SMSC Computer Hardware EMC2102 User Manual
Fan Speed Control with the EMC2102 Device  
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6.2.8  
Using the Tested Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38  
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List of Figures  
Figure 4.1 EMC2102 Fan Control Evaluation System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7  
Figure 4.2 EVB-EMC2102 Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7  
Figure 5.1 ChipMan Message for First Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8  
Figure 5.2 ChipMan Device Selection Window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9  
Figure 5.3 Selecting the Device and Master Controller Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10  
Figure 5.4 ChipMan Operation Window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10  
Figure 5.5 Changing Fan Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12  
Figure 5.6 Plotting from the ChipMan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12  
Figure 5.8 Plot Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13  
Figure 5.7 Plot Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13  
Figure 5.9 Plots for Proper Control Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14  
Figure 5.10 Effects of Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15  
Figure 5.11 Fan Control Parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16  
Figure 5.12 Forced Kick Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17  
Figure 5.13 60% Spin Level Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18  
Figure 5.14 Reduced Spin-up Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18  
Figure 5.15 Default Ramp Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20  
Figure 5.16 Default Step Size with Different UPDATE Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21  
Figure 5.17 Default UPDATE with Different Step Size Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21  
Figure 5.18 Exceptionally Slow Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22  
Figure 5.19 Update Time Modifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23  
Figure 5.20 Minimum Drive Setting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24  
Figure 5.21 Valid Tach Count Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24  
Figure 5.22 Fan Spin and Stall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27  
Figure 5.23 Fan Spin-up Routine Restarted Repeatedly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28  
Figure 5.24 Theoretical Plot of Case 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29  
Figure 5.25 Spin-up Case 1 Fix 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29  
Figure 5.26 Spin-up Case 1 Fix 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30  
Figure 5.27 Theoretical Plot of Case 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30  
Figure 5.28 Spin-up Case 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31  
Figure 5.29 Theoretical Plot of Case 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31  
Figure 5.30 Spin-up Case 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32  
Figure 5.31 Spin-up Routine Restarted During Normal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32  
Figure 5.32 Theoretical Plot of Case 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33  
Figure 5.33 Spin-up Case 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33  
Figure 5.34 Spin-up Case 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34  
Figure 5.35 Spin-up Case 5 Fix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34  
Figure 6.1 A Typical 2-pole DC Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35  
Figure 6.2 Output Signal of a 2-pole Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35  
Figure 6.3 Fan TACH Measurement With EMC2102 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36  
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List of Tables  
Table 5.1 Register Change Summary for Experiment 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15  
Table 5.2 Register Change Summary for Experiment 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19  
Table 5.3 Register Change Summary for Experiment 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22  
Table 5.4 Register Change Summary for Experiment 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25  
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1 Overview  
SMSC has introduced a series of Environmental Monitoring and Control (EMC) devices with integrated  
fan control. This fan controller family devices feature the advanced closed-loop fan control technology  
developed by SMSC’s engineering team.  
This user manual provides detailed information about fan control features supported by one of those  
EMC devices -- EMC2102, with detailed hand-on experiments for configuring the devices in real  
applications.  
2 Audience  
This user manual assumes that the reader is familiar with the functionality of the EMC2102 device and  
its evaluation board. The goal of the user manual is to help users to evaluate the new EMC device  
using Chip Manager (ChipMan) software provided by SMSC. This user manual also can be used as a  
reference material for other EMC devices which have fan control features.  
3 References  
The following documents should be referenced when using this user manual:  
„
„
„
„
EMC2102 Device Datasheet  
EVB-EMC2102 Evaluation Board User Manual  
EVB-EMC2102 Evaluation Board Schematics  
ChipMan Software User Manual  
4 The Evaluation System  
The evaluation system used for this user manual has two major parts, as shown in Figure 4.1,  
"EMC2102 Fan Control Evaluation System":  
„
„
An EMC2102 evaluation board (EVB-EMC2102) with on-board 5V DC fan (Figure 4.2)  
A PC with SMSC ChipMan software installed (requiring XML file for EMC2102 device)  
This user manual contains several groups of user experiments which cover most of the fan control  
features of the EMC2102 fan controller device. All examples are based on the 2102 device evaluation  
board (EVB-EMC2102) and its software, but the methods and the results will apply to other EMC2102  
applications.  
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USB Cable  
PC w/ ChipMan Software  
EVB-EMC2102  
Figure 4.1 EMC2102 Fan Control Evaluation System  
Figure 4.2 EVB-EMC2102 Board  
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5 Basic Operation Experiments  
In this chapter basic operation experiments will be provided to help users to get familiar with the  
system.  
5.1  
Experiment 1 - Manual Fan Control  
This experiment is designed to gain familiarity with both the EMC2102 device, and the application  
software, ChipMan.  
The ChipMan application can be used to configure the EMC2102 device and to monitor the status of  
the device. It includes tools to capture and plot data at rates up to 10Hz. Additionally, ChipMan can  
be used to review previously saved data.  
5.1.1  
ChipMan Installation  
Install the ChipMan application and device driver on a PC by running Setup.exe from the EMC2102  
Evaluation System Software CD provided by SMSC. A revision history and install/uninstall notes may  
be found in the readme.txt file on the disk.  
ChipMan uses definition files and data files to identify the devices it supports, to load specific values  
into registers, and monitor, plot, or record the values of any register set in the device. ChipMan  
definition files are XML files conforming to XML Version="1.0" and Encoding="utf-8". The data files for  
downloading values to the device are CMF files, specific to the ChipMan application.  
The CMF files may be located anywhere on the hard drive, but the XML files MUST reside in the  
ChipMan directory, typically located at: C:\Program Files\SMSC\ChipMan\Chips. An XML file usually  
names with the device name that supports (EMC2102.xml, EMC2103-2.xml, etc.)  
During the installation of the ChipMan application, it is possible to specify a non-default installation  
directory. If this was done, substitute the path provided at that installation for "C:\Program Files" to  
store the XML files in the proper location.  
Connect the USB cable to an available USB port on the PC, (The other end, “mini-B” end, of the USB  
cable should be connected to an EMC Evaluation Board). The “Find New Hardware” wizard will pop  
up on the PC’s screen for USB driver installation. Follow the instructions on the screen to complete  
the installation process.  
5.1.2  
Setting Up the ChipMan  
Once the ChipMan has been installed, start the software by selecting Start -> Programs -> SMSC ->  
Chip Manager. If this is the first operation, the application will guide you to select a device, as shown  
in Figure 5.1 below.  
Figure 5.1 ChipMan Message for First Operation  
Answer "Yes", then the device selection menu as shown in Figure 5.2, "ChipMan Device Selection  
Window" will appear.  
Click on the Pull-Down menu at the top, select EMC2102 as shown in Figure 5.3, "Selecting the Device  
and Master Controller Type", and click OK. The ChipMan operation window will then appear, as shown  
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in Figure 5.4, "ChipMan Operation Window". Click on the HWM icon to show the different windows  
available.  
The EMC2102 WatchDog will have timed out at this point, and the on-board DC fan will be running at  
100%.  
Note: Starting the ChipMan application without the USB cable/EVB connected to the PC, an error  
message "Supported company ID on device not found" will pop-up. Plug in the USB cable and  
click on “Abort”, another pop-up window will ask if you want to select an SMSC device. Click  
on “Yes” and then select the device as shown in Figure 5.3.  
In the same device selection window the user also has the options to chose the SMBus Slave Address  
(Default is 7A for EVB-EMC2102, use “Select automatically” is recommended), the Master Controller  
type (Default is USB SMBus Bridge, see note 1 below) and if the ChipMan needs to be configured to  
run in simulation mode. In the simulation mode, users can practice the software functions without  
connecting a USB cable/EVB to the PC.  
For more help with ChipMan, select Help -> Contents for an html based help document.  
Figure 5.2 ChipMan Device Selection Window  
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Figure 5.3 Selecting the Device and Master Controller Type  
Figure 5.4 ChipMan Operation Window  
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Notes:  
1. The EVB-EMC2102 needs to be configured using the USB SMBus Bridge to work properly. If in  
the device selection window the Master Controller type is set to I/O Controller Hub then the  
"Supported company ID on device not found" message will pop-up again.  
2. Disconnecting the USB cable and reconnecting it without restarting the ChipMan may cause  
register reading errors (all zeros). This problem can be cleared by re-selecting the EMC2102 device  
through the device selection window (Options -> Select Device).  
3. The SMBus Slave Address could vary depending on the device. If a correct XML file is installed,  
the ChipMan should be able to select the correct slave address automatically. Refer to the device  
datasheet for more details about the SMBus protocol and its configurations.  
4. The SMSC ChipMan application allows viewing and changing register values for a variety of  
devices. The ChipMan software only needs to be installed once to support all of these devices.  
The list of supported devices may be found in the pulldown menu under Options -> Select Device.  
The next step will be to load the CMF file. Simply select File at the top of the window, and "Import"  
from the pull-down menu. A pop-up window will let the user to locate the right CMF.  
Select the appropriate file and click "open". The CMF file will then load up the values into the EMC2102  
device.  
SMSC provides all CMF files for the operation experiments introduced in this user manual to help  
customers to evaluate the EMC2102 device. Customers can also export their own configurations to  
CMF files through the pull-down menu File -> Export/Export As.  
The CMF file used for the Experiment 1 is EMC2102_manual.cmf.  
To ensure the ChipMan application and the EMC2102 are communicating, select File -> Import and  
then select the file emc2102_manual.cmf. This will import a configuration file to disable EMC2102’s  
RPM control function and then set a valid fan control output value. The on-board DC fan’s speed will  
be reduced to about 5000 rpm at this time.  
Select "3: Fan Settings" in the ChipMan window by double-clicking. The window as shown in  
Figure 5.5, "Changing Fan Speed" will open. Double-click the "last value" of Fan Driver Setting register  
(51h) and enter a new drive value (should be greater than 9Ah for the on-board DC fan). The fan  
should respond, and the TACH Reading register (58h) should indicate an RPM reading.  
It is recommended to set Autorefresh Registers option in ChipMan for all experiments in this user  
manual. Select Options -> Autorefresh registers.  
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Figure 5.5 Changing Fan Speed  
5.1.3  
Plotting From ChipMan  
The ChipMan software has the ability to plot register values in real-time, up to 10Hz continuous rate.  
To select a register to plot, highlight its name or value, and right-click. A menu with a single entry "Add  
register to Plot" will appear (Figure 5.6, "Plotting from the ChipMan"). Click the entry then a plot window  
should appear, with a legend on top. When additional registers with the same data type are selected,  
they are added to the existing plot window. In the experiment shown in Figure 5.7, "Plot Windows",  
Drive Setting, TACH Target, and TACH Reading were selected. Note both the Tach registers are being  
plotted on the same graph.  
The last step is to start the plots. All plots can be started simultaneously by selecting the "Control"  
pulldown from the main application window and then "Plot -> start all plots". Individual plots may be  
paused at any time without loss of captured data on the other plot windows.  
Figure 5.6 Plotting from the ChipMan  
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Figure 5.7 Plot Windows  
The two plots shown in Figure 5.8, "Plot Examples" are in sync. If the scaled data is desired for  
analysis or archival, the data may be stored in a semi-colon separated text file from each of the plot  
windows. Simply select File Export, and enter a filename in the Save window.  
TACH Target (57h)  
Fan Driver Setting (51h)  
TACH Reading (58h)  
Figure 5.8 Plot Examples  
5.2  
Experiment 2 - RPM Based Closed-Loop Fan Control  
The experiment 2 is designed to gain familiarity with the closed-loop RPM controller implemented in  
the EMC2102. This experiment will discuss the effects of gain, spin-up, and minimum settings on the  
closed-loop performance.  
The cmf file for this experiment is EMC2102_RPM.cmf.  
5.2.1  
Getting Started  
For all these tests, the Fan Drive Setting register (51h), the TACH Target register (57h) and the TACH  
Reading registers (58h) are selected to plot. As bits are switched in each of the tests, the register name  
and address will be provided.  
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5.2.2  
Basic RPM Based Fan Control  
The EMC2102 defaults will enable closed-loop operation. Prior to other options, examine the various  
parameters on ChipMan window page 3: Fan Settings. The registers of most interest are the FAN  
Minimum Drive (55h), and Valid Tach Count (56h). The closed-loop controller will not drive below the  
minimum drive value, and will not respond to a TACH Target RPM speed less than the speed defined  
by the Valid Tach Count register.  
Note: The TACH reading is a reciprocal function of the fan speed, i.e. a higher TACH reading value  
means a slower fan rpm speed. Refer to 6 "Appendix" for more details.  
Same as Experiment 1, select Fan Drive Setting (51h), TACH Target (57h), and TACH Reading (58h)  
for plotting. Start the plot windows in order to see the response, and command a series of Tach  
Targets, starting at 4500 RPM, and going up in 500 RPM steps. The plots in Figure 5.9, "Plots for  
Proper Control Settings" will be representative of the response generated.  
TACH Target (57h)  
Fan Driver Setting (51h)  
TACH Reading (58h)  
Figure 5.9 Plots for Proper Control Settings  
Using this basic setup, it is possible to explore how well the fan is controlled using default values.  
5.2.3  
Effects of Loading  
The EMC2102 has the ability to overcome changes in fan current requirements for a given RPM setting  
due to aging, a blocked vent, dust, etc. This is because the controller does not rely on absolute drive  
settings, but rather on driving the PID loop error to "0" (i.e., driving the TACH reading to equal to the  
TACH target). To illustrate this feature, simply command an RPM setting (6000 RPM for this  
experiment), and then use a piece of paper to cover the window of the fan. This will reduce the air  
flow through the fan and decrease the wind resistance. With the same Fan Drive Setting value (~240d  
in register 51h, set by devices’ RPM controller), less wind resistance will make the fan running faster.  
Once the PID controller inside the EMC2102 detects the difference between the TACH reading and  
the TACH target (6000 RPM), it will adjust the output values (down to ~210d in this experiment) to  
bring the fan speed back to the target, as shown in Figure 5.10, "Effects of Loading".  
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Fan was covered  
The cover was removed  
Figure 5.10 Effects of Loading  
5.2.4  
Register Change Summary  
Table 5.1, "Register Change Summary for Experiment 2" lists all register value changes from the  
default cmf load to accomplish the tests.  
Table 5.1 Register Change Summary for Experiment 2  
REGISTER  
NAME  
DEFAULT  
VALUE  
NEW  
VALUE  
ADDRESS  
COMMENT  
Fan  
Configuration  
52h  
4Bh  
(0100 1011b)  
CBh  
(1100 1011b)  
Enables the RPM based closed-loop fan  
control Algorithm  
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5.3  
Experiment 3 - Spin-up Configuration Options  
This experiment is designed to gain familiarity with the various spin-up options available in the  
EMC2102 devices.  
This experiment will discuss the effects of Spin-Up Time and Spin-Up Levels. These parameters are  
important to ensure a valid start, while minimizing the turn-on overshoot for initial low RPM settings.  
(More examples regarding these two parameters can be found in Section 5.7.1, "Repetitious Spin-up  
Routine Caused by Incorrect Settings").  
The CMF file for this experiment is the same as for Experiment 1, EMC2102_default.cmf.  
5.3.1  
Fan Control Parameters  
The spin-up routine is a special algorithm that the EMC2102 uses to boot up the fan. In manual control  
(open loop) mode, it is only invoked when starting from a ‘0’ value in the FAN Drive Setting register  
51h.  
In the RPM control (closed-loop) mode, the spin-up routine is invoked when the device is driving a  
stalled fan to a valid target speed, i.e., the raw data value in register 57h (TACH Target) is smaller  
than the one in register 56h (Valid TACH Count). During the normal operation while the fan is running,  
the spin-up routine could also be invoked if the fan speed fell to below the valid fan speed, i.e, the raw  
data value in register 58h (TACH Reading) is greater than the one in register 56h (Valid TACH Count),  
since the fan will be considered as stalled by the controller.  
There are several parameters that control the fan’s behavior during and after the spin-up routine, as  
shown in Figure 5.11, "Fan Control Parameters".  
When the spin-up routine is operating, the fan driver is set to full scale for one quarter of the total user  
defined spin up time. For the remaining spin up time, the fan driver output is set a user defined level  
(60% or 75% of full drive). After the spin-up routine has finished, the RPM algorithm controls the fan  
speed to the TACH targets. At this point if the EMC2102 cannot detect a valid fan speed (the  
hexadecimal value in the TACH Reading register is higher than the Valid TACH Count register setting,  
which means the fan speed is below the valid speed), it will try to restart the fan.  
Fan Drive Setting  
(51h)  
Use Normal  
Closed-loop Algorithm  
Use Spin-Up Algorithm  
100%  
Spin Up Level =  
60% ~ 75%  
(53h[2])  
Fan Step  
(54h[5:0])  
New Target Count  
Algorithm controlled drive  
Prev Drive  
¼ of Spin Up Time  
Update Time  
(52h[2:0])  
Spin Up Time  
(53h[1:0])  
Check TACH  
Target Count  
Reached  
TACH Target  
Changed  
Figure 5.11 Fan Control Parameters  
The spin-up LEVEL (60% or 75%, defined by 53h[2]) has corresponding Fan Driver Setting  
hexadecimal values (register 51h) which cab be calculated using FFh as 100% and 00h as 0%. For  
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the 60% drive the register 51h value is 153d or 99h, and for 75% it is 191d or BFh. Those two drive  
settings will run a DC fan at two different speeds and we will call them rpm60 and rpm75. Depending  
on the fan, the speed for the same drive setting will vary.  
All data and plot examples in this document were taken using an EVB-EMC2102 board with the on-  
board DC fan. This fan has an rpm60 of 4500 rpm, and an rpm75 of 5650 rpm.  
5.3.2  
5.3.3  
Getting Started  
For all these tests, the Fan Drive Setting register (51h), the TACH Target register (57h) and the TACH  
Reading registers (58h) are selected to plot. As bits are switched in each of the tests, the register name  
and address will be provided.  
Forced Kick Function  
The EMC2102 has a forced 100% kick at turn-on. This feature drives the fan at maximum voltage for  
¼ of the time set by the SPINUP_TIME[1:0] bits in register 53h. The plots in Figure 5.12, "Forced Kick  
Function" illustrate this function with a spin-up time of 2.0 sec while the TACH Target register (57h) is  
changed from 0 rpm to 5200 rpm.  
Selecting a different "Time per Division" value in the pull-down menu in the center bottom of the plotting  
window, to make the 100% kick pulse can be viewed. This scale change affects both playback, and  
real-time mode. The rate at which data is recorded is unaffected by changing this parameter.  
100% Kick Pulse for 500 ms  
(1/4 of Spin-Up Time)  
75% Spin-Up  
Level  
Normal Fan Drive  
(for 5200 rpm)  
Spin-Up  
Time = 2 s  
Figure 5.12 Forced Kick Function  
5.3.4  
Spin-Up Level  
Depending on the application, the value of LEVEL (spin-up level, bit[1] in register 53h) may need to  
be adjusted to achieve the best fan control result. The plots in Figure 5.13, "60% Spin Level Setting"  
show the same experiment as Section 5.3.3, "Forced Kick Function" with a 60% spin-up level. Note  
the a smaller overshoot at the lower LEVEL setting.  
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Invalid TACH Count  
Figure 5.13 60% Spin Level Setting  
Note: When a fan starts, the first TACH count captured by the EMC2102 may not reflect the fan’s  
speed correctly, since the counting clock (32.768 kHz) could only partially fill the counting  
window, which will cause a higher speed reading. Also for some fans, the tachometer may not  
work immediately after the fan starts therefore some invalid TACH signals (very short, noisy  
pulses) could be sent out at the beginning. In either case, the invalid TACH counts could be  
displayed on the ChipMan plots (Figure 5.13), but will never be used to control the fan because  
the EMC2102 will not look at the TACH reading until the end of spin-up routine.  
5.3.5  
Spin-Up Time  
The EMC2102 FAN Spin Up Configuration register (53h) contains 2 bits to set the overall spin-up time.  
This parameter allows for tailoring of rapid and slow response fans. Repeat the experiment in  
Section 5.3.3 with 500 ms SPINUP_TIME. This will provide a quicker response with smaller overshoot,  
as shown in Figure 5.14, "Reduced Spin-up Time".  
In general, spin-up time should be tailored for the fan type being used or the effect may be undesirable.  
Figure 5.14 Reduced Spin-up Time  
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5.3.6  
Register Change Summary  
Table 5.2, "Register Change Summary for Experiment 3" lists all register value changes from the  
default cmf load to accomplish the tests.  
Table 5.2 Register Change Summary for Experiment 3  
REGISTER  
NAME  
DEFAULT  
VALUE  
NEW  
VALUE  
ADDRESS  
COMMENT  
SPINUP_TIME of 2.0 sec  
Change the LEVEL from 60% to 75%  
FAN Spin Up  
Configuration  
53h  
01h  
(00000001b)  
03h  
05h  
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5.4  
Experiment 4 - RPM Drive Mode Rate Controls  
This experiment is designed to gain familiarity with the rate control options available in the EMC2102  
devices.  
This experiment will discuss the effects of Maximum Fan Step and Update rate that can be used to  
control the ramp rate of a fan. The two parameters ensure the fan reaches the desired drive in a  
reasonable time with no oscillations.  
The CMF file for this experiment is the same as for Experiment 1, EMC1202_default.cmf.  
5.4.1  
5.4.2  
General Setup  
For all these tests, the Fan Drive Setting register (51h) and the TACH Reading registers (58h) are  
selected to plot. As bits are switched in each of the tests, the register name and address will be  
provided.  
Controlling the Ramp Rate  
Controlling the ramp rate can improve the performance of the fan control loop by limiting the slew rate  
of the fan drive. The EMC2102 uses the UPDATE bits in the FAN Configuration register (52h, bits [2:0])  
to determine the time interval between two updates of the controller output, and uses the FAN Step  
register (54h) to determine the maximum allowed hexadecimal count (STEP) of the output (Refer to  
Figure 5.11 "Fan Control Parameters" for more details). These two parameters can only work in the  
RPM control mode. When the RPM control function is disabled (52h[7]= 0), any change in the Fan  
Drive Setting register (51h) will immediately change the output.  
The plots in Figure 5.15, "Default Ramp Rate" illustrate the drive and response with the default  
UPDATE (400ms) and default STEP SIZE (Max. 16 drive settings per update), while changing the fan  
target speed from 4000 rpm to 6000rpm.  
Figure 5.15 Default Ramp Rate  
The ramping rate in this mode can be accelerated or slowed down, depending on application and the  
values of register 52h (UPDATE) and 54h (STEP SIZE). In the next experiment (Figure 5.16, "Default  
Step Size with Different UPDATE Settings"), the default STEP SIZE with different UPDATE (400 ms  
and 100 ms) were used, The 100 ms setting has the effect of speeding the loop up by a factor of 4,  
as that is the ratio between minimum (100ms) and default (400ms) UPDATE settings.  
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UPDATE  
= 100 ms  
UPDATE  
= 400 ms  
Figure 5.16 Default Step Size with Different UPDATE Settings  
In the next experiment (Figure 5.17, "Default UPDATE with Different Step Size Settings"), two different  
maximum step sizes, 16 and 63, were used. with the 63 STEP SIZE setting, the output takes less  
steps (updates) from 4000 rpm to 7500 rpm because it gives the fan more power to follow the desired  
rpm settings.  
STEp SIZE  
= 63  
STEp SIZE  
= 16  
Figure 5.17 Default UPDATE with Different Step Size Settings  
In the last experiment, an extremely slow ramp rate is demonstrated. The UPDATE was set to  
maximum (1600 ms), and the STEP SIZE was changed to 01h (Figure 5.18, "Exceptionally Slow  
Rate"). Note the large scale of the “Time per division” in the figure.  
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Figure 5.18 Exceptionally Slow Rate  
5.4.3  
Register Change Summary  
Table 5.3, "Register Change Summary for Experiment 4" lists all register value changes from the  
default cmf load to accomplish the tests.  
Table 5.3 Register Change Summary for Experiment 4  
REGISTER  
NAME  
DEFAULT  
VALUE  
NEW  
VALUE  
ADDRESS  
COMMENT  
FAN Step  
54h  
52h  
10h  
01h  
Demonstrate RRC long duration  
Fan  
Configuration  
CBh  
C8h, CFh  
Demonstrate min (C8h) and max (CFh) UPDATE rates  
applied to RRC  
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5.5  
Experiment 5 - Optimizing RPM Control Response  
This experiment is designed to gain familiarity with the parameters that affect the closed-loop controller  
implemented in the EMC2102. All these registers are located on the Fan Setting page in ChipMan.  
This experiment will go through each register, examining the effects of parametric changes on the  
closed-loop controller in RPM mode.  
5.5.1  
5.5.2  
General Setup  
For all these tests, the Fan Drive Setting register (51h), the TACH Target register (57h) and the TACH  
Reading registers (58h) are selected to plot. As bits are switched in each of the tests, the register name  
and address will be provided.  
Fan Configuration Register (52h)  
The Fan Configuration Register stores the basic operation parameters of the closed-loop controller.  
The EN bit turns on the RPM controller, and locks out manual updates to the Fan Drive Setting register  
(51h).  
The next two parameters, LIMIT2K and EDGES[1:0] (both in register 52h) describe the fan itself. The  
EDGES[1:0] tell the controller how many tach edges to examine to determine the fan speed. The  
LIMIT2K parameter tells the RPM controller how to interpret the TACH Target register (57h). The value  
of this parameter provides an operating range for the fan by specifying the minimum rpm: the 500 rpm  
setting is for low speed fans and the 2000 rpm setting is typical for notebook and desktop fans (high  
speed fans). (Please refer to Section 6.1, "DC Fan Basics - Poles, Tach Meter Pulses and Edges" for  
more details about the TACH edges and ranges.)  
For all experiments in this suite, the default values have been used. This keeps the scaling of those  
values fixed, allowing the ChipMan application to appropriately scale the counts to RPM values.  
The UPDATE[2:0] parameter controls the speed at which the RPM controller updates the output drive,  
as already been discussed in Section 5.4, "Experiment 4 - RPM Drive Mode Rate Controls". This  
parameter is independent of the TACH Reading updates, which are controlled by the EDGES[1:0]  
parameter. The plots in Figure 5.19, "Update Time Modifications" show the effect of UPDATE on the  
closed-loop performance when starting the on-board fan. The numbers (in unit of second) in the left  
plot indicate the UPDATE value used for that sequence. By experimenting with the different update  
times you can determine the most stable setting for the fan to be controlled.  
0.1s  
0.2s  
0.4s  
0.8s  
1.6s  
Invalid TACH signals  
(Ignored by Controller)  
Figure 5.19 Update Time Modifications  
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5.5.3  
FAN Minimum Drive Register (55h) and Valid TACH Count (56h)  
These two registers assist the user in defining the operational environment for a given fan. The  
Minimum Drive register is an absolute minimum value the RPM controller may drive to in an attempt  
to achieve low RPM settings. The Valid Tach Count register is used to compare against the Tach Target  
register. No value less than the Valid Tach Count will be accepted by the controller. To examine this  
feature, set the minimum drive to C0h, and command an RPM setting of less than 5500 RPM. The fan  
will start at about 5600 rpm (51h = C0h). Set the target to 6000 rpm, and the fan speed follows. Drop  
the fan target speed from 6000 rpm to 4500 rpm, the real fan speed will only drop to about 5560 rpm,  
as shown in Figure 5.20, "Minimum Drive Setting".  
Fan starts at  
Minimum Drive  
Fan will not run below  
Minimum Drtive  
Figure 5.20 Minimum Drive Setting  
Likewise, the Valid TACH Count register operation is simple to show. Start the fan at 6000 RPM with  
all default setting, and then set the Valid TACH register to 5000 RPM. Enter a command of 4800 RPM,  
and the fan will not respond as shown in Figure 5.21, "Valid Tach Count Setting".  
Target of 4800 rpm  
Figure 5.21 Valid Tach Count Setting  
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5.5.4  
Register Change Summary  
Table 5.4, "Register Change Summary for Experiment 7" lists all register value changes from the  
default cmf load to accomplish the tests.  
Table 5.4 Register Change Summary for Experiment 7  
REGISTER  
NAME  
DEFAULT  
VALUE  
NEW  
VALUE  
ADDRESS  
COMMENT  
Fan  
52Bh  
CBh  
ABh  
4Bh  
Disable RPM based fan control algorithm  
Demonstrate UPDATE effect  
Configuration  
C8h - CFh  
5000d  
Valid Tach  
Count  
56H  
2010d  
Changed from 2010 RPM to 5000 RPM to show  
the effect in closed-loop  
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5.6  
Experiment 6 - Limits and Alerts  
This experiment is designed to gain familiarity with the control registers for generating fan related  
alarms and alerts associated with the EMC2102.  
The CMF file for this experiment is EMC2102_default.cmf.  
5.6.1  
5.6.2  
General Setup  
For all these tests, the Fan Drive Setting register (51h), the TACH Target register (57h) and the TACH  
Reading registers (58h) are selected to plot. As bits are switched in each of the tests, the register name  
and address will be provided.  
Fan Spin and Stall Interrupts  
The Configuration/Status page in the ChipMan application contains all the Interrupt configuration and  
status registers for the fan. In this experiment, the Fan Stall and Fan Spin status bits will be checked.  
In order to see the status bits change, the Interrupt Status 2 register (23h) is plotted along with other  
registers listed above. The Interrupt Mask register (24h) should be set to 10h (default) for this set of  
experiments.  
Start the plotting function within ChipMan, and force the fan to stop spinning. This will induce a Fan  
Stall condition. The plot of the Status Register will show a peak of 1 count for the stall condition,  
followed by peaks of 2 counts for each time the spin-up routine is invoked, as shown in Figure 5.22,  
"Fan Spin and Stall". In order to see the spikes mentioned above, the max scale on the register 27h  
plot needs to be modified. To do this, simply double click the 255 at the top of the "Y" axis, type a  
different maximum value (10) and enter. And then double click the 0 at the bottom of the "Y" axis, type  
a minimum value and enter. The scale will be changed.  
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TACH Target (57h)  
Fan Drive Setting  
(51h)  
TACH Reading (58h)  
Stall  
Interrupt Status 2  
(23h)  
Figure 5.22 Fan Spin and Stall  
5.6.3  
Register Change Summary  
All register values are default for the tests in this section.  
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5.7  
Experiment 7 - Troubleshooting  
5.7.1  
Repetitious Spin-up Routine Caused by Incorrect Settings  
At the end of spin-up routine (see Section 5.3.1, "Fan Control Parameters"), the EMC2102 checks the  
TACH Reading register (58h). If the value in this register is greater than the Valid TACH Count (56h),  
which means the fan is running at a speed slower than the minimum valid speed, the spin-up routine  
will be restarted (Figure 5.23, "Fan Spin-up Routine Restarted Repeatedly").  
Figure 5.23 Fan Spin-up Routine Restarted Repeatedly  
Depending on the fan characters and EMC2102 settings, there are several situations at the end of  
spin-up routine which will be discussed.  
Notes: For ease of understanding, all TACH values will be converted to RPM values in the following  
examples.  
5.7.1.1  
Case 1 - Spin-up Lvel RPM < Valid RPM < Target RPM  
In this case, the spin-up level rpm (rpm60 or rpm75) is smaller than both valid rpm (function of 56h)  
and target rpm (function of 57h). The theoretical plot of this situation is shown in Figure 5.24,  
"Theoretical Plot of Case 1".  
Since the fan speed at the end of spin-up routine is always below the minimum valid speed (a function  
of 56h), the EMC2102 will think the fan is not running, and will try to restart the fan with spin-up routine  
over and over.  
Using the EVB-EMC2102 to test this situation with rpm60 (~4500 rpm), simply set the Valid TACH  
register (56h) with 4800 rpm and start the fan with TACH Target (57h) = 5000 rpm. The repeating spin-  
up routines can be observed (Figure 5.25, "Spin-up Case 1 Fix 1").  
For rpm75 (~5650 rpm), set 56h = 6000 rpm and 57h = 6500 rpm, as shown in Figure 5.26, "Spin-up  
Case 1 Fix 2".  
There are mainly two ways to fix this problem. If the spin-up LEVEL in 53h is 60%, then change it to  
75%, as shown in Figure 5.25.  
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Fan Speed  
(RPM)  
RPM for  
100% Drive  
Target Speed  
Valid Speed  
rpm60 or rpm75  
Fan Speed  
¼ of Spin Up Time  
Spin Up Time  
Check TACH  
Figure 5.24 Theoretical Plot of Case 1  
Spin Up Level  
Changed to 75%  
Figure 5.25 Spin-up Case 1 Fix 1  
If the fan is already set to 75% level, we will need to lower the valid speed (function of 56h, Valid  
TACH) to a value below the rpm75, to fix the problem.  
To test this situation, set spin-up level to 75% (53h[2] = 1), set the Valid TACH Count (56h) = 6000  
rpm and then start the fan (57h) with 6500 rpm. The spin-up routine will run repeatedly.  
Change the Valid TACH Count (56h) to 5800 rpm, the problem cannot be fixed since the valid speed  
is still higher than the fan speed (rpm75 = 5650 rpm).  
Set 56h = 5580 rpm which is below 5650 rpm (the rpm75), the system gets out of the spin-up routine  
(Figure 5.26).  
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Valid Speed = 6000 rpm  
Fan Drive Setting (51h)  
Valid Speed = 5800 rpm  
Valid Speed = 5580 rpm  
Figure 5.26 Spin-up Case 1 Fix 2  
5.7.1.2  
Case 2 - Valid RPM << Target RPM < Spin-up Level RPM  
In this case, the target speed is smaller than the spin-up level speed (rpm60 or rpm75) and is much  
bigger than the valid speed. The theoretical plot of this situation is shown in Figure 5.27, "Theoretical  
Plot of Case 2".  
Since the fan speed at the end of spin-up routine is always higher than the minimum valid speed, the  
EMC2102 will go to the normal operation after the spin-up routine.  
Using the EVB-EMC2102 to test this situation with rpm75 (~5650 rpm), simply set the Valid TACH  
register (56h) with 4500 rpm and start the fan with TACH Target (57h) = 5500 rpm (Figure 5.28, "Spin-  
up Case 2").  
Fan Speed  
RPM for  
(RPM)  
100% Drive  
rpm60 or rpm75  
Fan Speed  
Target Speed  
Valid Speed  
¼ of Spin Up Time  
Spin Up Time  
Check TACH  
Figure 5.27 Theoretical Plot of Case 2  
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Fan Drive Setting (51h)  
Figure 5.28 Spin-up Case 2  
Case 3 - Valid RPM =< Target RPM << Spin-up Level RPM  
5.7.1.3  
In this case, the target speed is only a little greater than the valid speed, and both of them are much  
smaller than the spin-up level speed (rpm60 or rpm75). The theoretical plot of this situation is shown  
in Figure 5.29, "Theoretical Plot of Case 3".  
Fan Speed  
RPM for  
(RPM)  
100% Drive  
rpm60 or rpm75  
Fan Speed  
Target Speed  
Valid Speed  
¼ of Spin Up Time  
Spin Up Time  
Check TACH  
Figure 5.29 Theoretical Plot of Case 3  
Since the fan speed at the end of spin-up routine is higher than the minimum valid speed, the  
EMC2102 should go to the normal operation after the spin-up routine. However, because the large  
speed difference between the spin-up level speed (rpm60 or rpm75) and the target speed, the closed-  
loop controller will try to make a big adjustment of its output to reach the target speed. With incorrect  
settings (such as big output step or short update time), this adjustment could easily cause an  
undershoot and make the fan speed below the valid rpm, and than make the spin-up routine restart.  
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Using the EVB-EMC2102 to test this situation with rpm75 (~5650 rpm), simply set the Valid TACH  
register (56h) with 4500 rpm, set the UPDATE (52h[2:0]) = 100ms and start the fan with 4700 rpm, the  
spin-up routine starts over ‘and over (Figure 5.30, "Spin-up Case 3").  
To fix this problem, change the UPDATE (52h[2:0]) back to 400 ms. It will give the fan more time to  
reach the speed of the previous step and reduce the overshoot/undershoot. Another solution is to  
decrease the Fan Step settings which will force the controller to take smaller steps to achieve the target  
speed.  
When the target speed is too close to the valid speed, the problem will not only occur when the fan  
starts. It may also cause problems in the normal operation after the spin-up, since the fan speed  
reading errors (caused by fan load changes, tachometer truncation errors, circuit noises, etc.) could  
drop it below the valid speed and cause a spin-up routine restart. (Figure 5.31, "Spin-up Routine  
Restarted During Normal Operation").  
UPDATE = 400 ms  
UPDATE = 100 ms  
Undershoots cause  
the fun runs below  
valid speed  
Figure 5.30 Spin-up Case 3  
Figure 5.31 Spin-up Routine Restarted During Normal Operation  
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5.7.1.4  
Case 4 - 4.Valid RPM < Spin-up Level RPM (rpm60 or rpm75) < Target RPM  
In this case, the spin-up level speed (rpm60 or rpm75) is greater than the valid speed and smaller than  
the target speed, as shown in Figure 5.32, "Theoretical Plot of Case 4".  
At the end of spin-up routine, the closed-loop control will drive the fan up to reach the target, therefore  
the fan speed will never be lower than the valid speed. The EMC2102 will go to the normal operation  
after the spin-up routine.  
Using the EVB-EMC2102 to test this situation with rpm60 (~4500 rpm), simply set the Valid TACH  
register (56h) with 3500 rpm and start the fan with TACH Target (57h) = 5000 rpm (Figure 5.33, "Spin-  
up Case 4").  
Fan Speed  
RPM for  
(RPM)  
100% Drive  
Target Speed  
rpm60 or rpm75  
Fan Speed  
Valid Speed  
¼ of Spin Up Time  
Spin Up Time  
Check TACH  
Figure 5.32 Theoretical Plot of Case 4  
Figure 5.33 Spin-up Case 4  
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5.7.1.5  
Case 5 - Correct RPM Relationships with a Slow Response DC Fan  
In this case, the spin-up routine is too short to make the fan reach a speed higher than the valid speed.  
Since the EMC2102 cannot detect a valid TACH at the end of spin-up routine, it will try to restart the  
fan. Depending on the fan, it is possible that after several spin-up cycles, the fan can reach the valid  
speed and operate normally.  
Using the EVB-EMC2102 to test this situation with rpm60 (~4500 rpm), simply set the SPINUP_TIME  
(53h[1:0]) = 250 ms, Valid TACH (56h) = 4400 rpm, and start the fan with TACH Target (57h) = 5500  
rpm. Multiple spin-up routines will be observed (Figure 5.34, "Spin-up Case 5").  
Figure 5.34 Spin-up Case 5  
To fix this problem, stop the fan and set the SPINUP_TIME = 2s, and restart the fan with 5500 rpm.  
Increasing Spin-up time will make a longer 100% "kick" time and provide the fan with more power to  
speed-up (Figure 5.35, "Spin-up Case 5 Fix").  
The problem also can be fixed by changing the spin up level from 60% to 75% if not done already, as  
previously discussed.  
Longer 100% kick provides more  
driving power to speed-up the fan  
Figure 5.35 Spin-up Case 5 Fix  
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6 Appendix  
6.1  
DC Fan Basics - Poles, Tach Meter Pulses and Edges  
An n-pole fan has n pairs of North-South magnetic poles which are generated by electromagnet coils.  
At anytime, only one pair of coils are driven and which coil pair gets driven is determined by a  
component called Hall Sensor. The architecture of a typical 2-pole DC fan is shown in Figure 6.1, "A  
Typical 2-pole DC Fan".  
Protection  
Diode  
VDD  
Hall  
Motor  
Winding  
1
Motor  
Winding  
2
Sensor  
N +  
-
TACH  
1
S -  
S -  
+
+
Motor  
Winding  
Driver  
Hall  
Sensor  
-
N +  
GND  
Figure 6.1 A Typical 2-pole DC Fan  
The output of the hall sensor is also the TACH (or Tachometer) signal. When the magnetic field around  
the Hall Sensor changes its direction, the sensor’s output level will follow the change to create a square  
wave signal as shown in Figure 6.2, "Output Signal of a 2-pole Fan".  
Assuming 2-pole fan is running at a speed of 6000 RPM, it will rotate 100 revolutions per second. With  
2 pulses per revolution, the TACH pulse signal frequency will be 200Hz (Figure 6.2). Since a higher  
RPM will yield a higher TACH frequency, or a shorter period between pulses, the TACH signal can be  
used by the EMC devices to determine the speed of the fan. Generally speaking, we have:  
TACH Pulse Frequency (in HZ) = (RPM / 60) x (# of Pole)  
1 complete fan revolution  
= 2 pulses (5 edges)  
Fan Tach Signal  
Figure 6.2 Output Signal of a 2-pole Fan  
EMC2102 uses a clock (32.768KHz for example) to fill in a window between a programmable number  
of Tachometer edges. A counter starts on a specific rising edge and keeps counting until it sees the  
‘set’ number of edges, and then saves the counted pulse numbers into register 58h, the TACH Reading  
register.  
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Note: Although users can set the number of edges (in register 52h) to either 3, 5, 7 or 9, it is strongly  
recommended using the default value 5 while driving a 2-pole DC fan. This equal to one  
complete fan revolution for a 2-pole fan.  
5 EDGES  
3 EDGES  
Fan Tach Signal  
7 EDGES  
32.768kHz  
Clock  
n-EDGE WINDOW  
TWINDOW  
Figure 6.3 Fan TACH Measurement With EMC2102  
ChipMan translates TACH counts to the RPM value and displays the fan speed. For applications not  
using ChipMan software, the following equation can be used to convert the TACH Reading values to  
the real RPM speeds.  
where:  
EDGES = number of edges set by register 52h[4:3]  
EDGES −1 983040  
RPM =  
*
* m  
COUNT = TACH Reading (58h) value  
[1]  
Poles  
COUNT  
Poles = number of pole pairs in the DC fan  
m = factor defined by LIMIT2K (52h[6])  
(m = 1 for 500 rpm and m = 4 for 2000 rpm)  
6.2  
Characterizing a DC Fan with EVB-EMC2102 and ChipMan  
As a very important component in the closed-loop, the DC fan’s characteristics have a great impact  
on the control system’s performance. Using the EVB-EMC2102 and ChipMan software tool, a 5V DC  
fan’s characteristics can be easily tested.  
In general, the following parameters need to be characterized:  
„
„
„
„
„
Minimum Startup Speed  
Stall Speed  
Minimum Valid TACH Speed  
Maximum Fan Speed  
Spin-up Level (i.e., rpm60 and rpm75. Refer to Section 5.3.1, "Fan Control Parameters" for more  
details)  
6.2.1  
General Setup  
„
Setup the system and make sure the hardware and software are working as discussed in Section  
5.1, "Experiment 1 - Manual Fan Control".  
„
„
Unplug the on-board DC fan from connector P1  
Connect the DC fan to be tested to P1 (refer to EVB-EMC2102 User Manual for the DC fan  
connector pinouts)  
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„
Verify the device is in Manual Mode (52h[7] = 0)  
6.2.2  
6.2.3  
Set the Correct LIMIT2K Value  
„
Register 52h (FAN Configuration) bit 6 (LIMIT2K) is a fan dependent parameter as discussed in  
Section 5.5.2, "Fan Configuration Register (52h)". When reading the TACH Reading register (58h),  
ChipMan uses the default LIMIT2K value (2000 rpm) to convert it to an rpm speed  
„
If the RANGE is set to 500 rpm, the TACH Reading value on the ChipMan display should be  
multiplied by 0.5  
Determine the Number of Poles and the Maximum Fan Speed  
„
„
„
Set the device in Manual Mode (52h[7] = 0)  
Start the fan with 100% output drive (register 51h = 255h)  
EMC2102 assumes that it is driving a 2-pole fan by default. If the fan speed in register 58h does  
not match the fan’s maximum speed specified in its datasheet, then it is not a 2-pole fan. The  
EDGES value in register 52h has to be modified, or all speed readings displayed by ChipMan have  
to be re-calculated using Equation 1  
„
The value in 58h also can be compared to the fan’s tachometer output frequency obtained by an  
oscilloscope to verify its correctness  
„
„
Record the rpm values in the TACH Reading register (58h) as the maximum fan speed  
The maximum fan speed for the EVB-EMC2102 on-board DC fan is about 7000 rpm  
6.2.4  
Determine the Minimum Startup Speed  
„
„
„
„
Set the device in Manual Mode (52h[7] = 0)  
Write a value (for example 80h) to Fan Driver Setting register (51h)  
If the fan cannot start, then increase the drive value until the fan start  
If the fan starts at the first drive value, then stop the fan (51h = 0) and write a smaller value to  
register 51h  
„
„
Repeat the above steps until the minimum startup speed is determined. Record the drive value in  
51h and the fan speed in register 58h  
The minimal start speed for the EVB-EMC2102 on-board DC fan is about 4500 rpm with output  
drive of 9Eh  
6.2.5  
6.2.6  
Determine the Stall Speed  
„
„
„
While the fan is running, reduce the fan drive value in register 51h, step by step, until the fan stops  
Write down the drive value in 51h and the fan speed in register 58h before the fan stops  
The stall speed for the EVB-EMC2102 on-board DC fan is about 3000 rpm (~70h)  
Determine the Minimum Valid TACH Speed  
„
„
„
„
While the fan is running in non-RPM mode, reduce the fan drive value in register 51h, step by step  
Monitor the rpm values in the TACH Reading register (58h)  
Using an oscilloscope to observe the fan’s Tachometer signal  
When invalid, the TACH signal will become erratic with incorrect values (usually much less TACH  
counts or very high rpm) in register 58h  
„
The TACH signal may be valid until the fan stalls. If it happens, the fan’s stall speed could be used  
as the minimum valid TACH speed  
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6.2.7  
6.2.8  
Determine the Spin-up Levels (rpm60 and rpm75)  
„
Drive the fan with 60% of the maximum output (register 51h = 99h) and the rpm value in the TACH  
Reading register (58h) will be the fan’s rpm60  
„
Drive the fan with 75% of the maximum output (register 51h = BFh) and the rpm value in the TACH  
Reading register (58h) will be the fan’s rpm75  
Using the Tested Parameters  
All parameters discussed above will vary from fan to fan and with fan aging, therefore some margins  
have to be added when selecting the fan control settings. A minimum of 10% of full fan speed is  
recommended for margins.  
6.2.8.1  
6.2.8.2  
6.2.8.3  
Spin-up LEVEL (Register 53h[2])  
This parameter has to be set so that the corresponding fan speed is greater than Minimum Startup  
Speed + Margin.  
Minimum Fan Speed  
To avoid stalling, the fan speed (a function of Fan Driver Setting [51h] or a function of TACH Target  
[57h]) needs to be greater than Stall Speed + Margin at all times.  
Valid TACH Count Speed (Function of Register 56h)  
The EMC2102 will not respond to any TACH Target (57h) value that has a corresponding speed slower  
than Minimum Valid TACH Speed + Margin, unless the value is FFh which will stop the fan. This  
ensures that the RPM control algorithm will not drive too low.  
6.2.8.4  
Maximum Fan Speed  
Use the measured maximum fan speed minus margin as the Maximum Fan Speed.  
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