Maxim Switch HFRD 340 User Manual
Reference Design:  
HFRD-34.0  
Rev. 3; 05/08  
REFERENCE DESIGN  
4 x 4 DVI KVM Switch  
Maxim Integrated Products  
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4 Application Diagrams  
HFRD-34.0 can be configured in a variety of application environments. Three possible applications are  
shown in Figures 1 through 3 below.  
DVI KVM SWITCH - App1  
(2-Person Work Station)  
USER 2  
USER 1  
DVI KVM Reference Design  
SHARED  
Figure 1. Typical application.  
DVI KVM SWITCH - App2  
(4-Person Work Station)  
USER 1  
USER 2  
USER 3  
USER 4  
DVI KVM Reference Design  
SHARED  
Figure 2. Typical application.  
Reference Design HFRD-34.0 (Rev.3, 05/08)  
Maxim Integrated Products  
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DVI KVM SWITCH - App3  
(Single User Work Station)  
USER 1  
DVI KVM Reference Design  
SHARED  
Figure 3. Typical application.  
5 Functional Diagrams  
HFRD-34.0  
Top-Level Functional Diagram  
DVI In2  
DVI Out1  
DVI Out2  
DVI Out3  
DVI Out4  
DVI In3  
Video Section  
MAX3845  
MAX4814  
MAX3814  
MAX3208  
Audio  
In3  
Audio  
In2  
Audio  
In4  
Audio  
In1  
Audio Section  
USB Section  
MAX4550  
MAX9723  
MAX9728  
Power  
USB2512  
USB2513  
MAX4906  
MAX3207  
MAX1953  
MAX1563  
MAX1853  
Controller  
ATMEGA168  
NAV  
Switch  
LCD Display  
USB  
HUB1  
USB  
HUB2  
Figure 4. HFRD-34.0 Top-level functional diagram.  
Reference Design HFRD-34.0 (Rev.3, 05/08)  
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Video-Section Functional  
I2C  
Diagram  
5
MAX4814  
x2  
5
5
5
Low-Speed Video Signals  
High-Speed Video Signals  
8
8
8
MAX3208  
MAX3814  
x2  
MAX3208  
x2  
DVI Out1  
DVI Out2  
DVI Out3  
DVI Out4  
DVI In1  
DVI In2  
DVI In3  
DVI In4  
MAX3208  
MAX3814  
x2  
MAX3208  
x2  
MAX3845  
x2  
MAX3208  
MAX3814  
x2  
MAX3208  
x2  
8
MAX3208  
MAX3814  
x2  
MAX3208  
x2  
Equalizers  
ESD  
ESD  
Switch/MUX  
Figure 5. Video-section functional diagram.  
Audio-Section Functional  
Diagram  
I2C  
MAX9723  
Audio  
In1  
Audio  
Out1  
Headphone  
Driver  
2
TVS  
MAX9723  
Audio  
In2  
TVS  
TVS  
Audio  
Out2  
MAX4550  
x2  
2
2
Headphone  
Driver  
TVS  
TVS  
With Click/Pop  
Suppression  
TVS  
Audio  
In3  
MAX9728  
Audio  
Out3  
2
TVS  
Line Out  
Driver  
TVS  
ESD  
MAX9728  
ESD  
Audio  
In4  
Audio  
Out4  
Line Out  
Driver  
Switch  
Audio Buffers  
Figure 6. Audio-section functional diagram.  
Reference Design HFRD-34.0 (Rev.3, 05/08)  
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USB-Section Functional  
I2C  
Diagram  
2
4
4
4
4
USB HUB 1  
2 - Port  
MAX3207  
USB2512  
MAX3208  
MAX3208  
MAX3208  
USB 1  
USB 2  
USB 3  
USB 4  
2
2
2
USB HUB 2  
2 - Port  
MAX3207  
MAX3207  
USB2512  
MAX4906  
x8  
USB HUB 3  
2 - Port  
USB2512  
USB2513  
USB HUB 4  
2 - Port  
MAX3207  
MAX3208  
HUB  
Controllers  
Switches  
ESD  
ESD  
Data  
Power  
2
2
MAX1558  
MAX1558  
MAX1558  
MAX1558  
MOSFETs  
x12  
2
2
Power  
Switches  
Main Supply  
Overcurrent  
Protection  
Figure 7. USB-section functional diagram.  
Reference Design HFRD-34.0 (Rev.3, 05/08)  
Maxim Integrated Products  
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6 IC Summary  
digital video equalizers, power-management  
products, and audio drivers. For additional  
information about other Maxim products for this  
and many other applications, please visit:  
www.maxim-ic.com.  
A summary of the ICs used in this reference  
design is provided below, along with links to  
additional information for each device.  
HFRD-34.0 demonstrates the operation of a small  
sample of Maxim’s digital and analog switches,  
Video Section Components  
Part Number  
Functional Description  
The MAX3845 is a TMDS® 2-to-4 fanout switch and cable driver for multimonitor distribution  
of DVI or HDMI™ (high-definition multimedia interface) signaling up to 1.65Gbps. Both inputs  
and outputs are standard TMDS signaling, as per DVI and HDMI standards. Because TMDS  
links are “point-to-point,” buffering is required for fanout applications. Four DVI/HDMI TMDS  
outputs are provided for fanout distribution. Each TMDS output can be independently  
sourced from either input or can be turned off. Each TMDS input or output is composed of  
four differential channels that can be arbitrarily assigned to the three data signals and the  
1/10th-rate clock. The data rate depends on resolution, but it can vary from 250Mbps (VGA)  
to 1.65Gbps (UXGA or 1080p/60).  
MAX3845  
Typical applications include multiroom display of the same video source, and industrial and  
commercial signage applications such as airport monitors or trading-room floor displays. The  
MAX3845 includes selectable output preemphasis that extends output cable reach up to an  
additional 7m.  
Additional information:  
www.maxim-ic.com/MAX3845  
The MAX3814 TMDS EQ/driver compensates for FR-4 and cable losses to the DVI/HDMI  
transmit connector, and provides a fully compliant DVI/HDMI TMDS output. The device can  
also be used in DVI/HDMI cable applications to extend reach and improve jitter margin of  
cable channels at the receive-side connector.  
MAX3814  
Additional information:  
www.maxim-ic.com/MAX3814  
The MAX4814E bidirectional 2:4 HDMI switch provides routing for low-frequency signals. The  
MAX4814E operates from a single +5.0V ±10% supply voltage and is ideal for connecting  
multiple HDMI sources to multiple loads.  
MAX4814E  
MAX3208  
Additional information:  
www.maxim-ic.com/MAX4814  
The MAX3208E is a low-capacitance, ±15kV ESD-protection diode array with an integrated  
transient voltage suppressor (TVS) clamp. The device is suitable for high-speed and general-  
signal ESD protection. Low input capacitance makes this device ideal for ESD protection of  
signals in HDTV; PC monitors (DVI, HDMI); PC peripherals (FireWire®, USB 2.0); server  
interconnect (PCI Express®, Infiniband®); datacom; and interchassis interconnect.  
Additional information:  
www.maxim-ic.com/MAX3208  
Reference Design HFRD-34.0 (Rev.3, 05/08)  
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USB Section Components  
Part Number  
Functional Description  
The MAX4906F analog multiplexer combines the low on-capacitance (CON) and low on-  
resistance (RON) necessary for high-performance switching applications. This device is  
designed for USB 2.0 Hi-Speed applications at 480Mbps. The MAX4906F also handles all  
the requirements for USB low- and full-speed signaling.  
MAX4906F  
Additional information:  
www.maxim-ic.com/MAX4906F  
SMSC’s USB251x is a family of versatile, cost-effective, and power-efficient USB 2.0 hub  
controllers. Leveraging innovative MultiTRAK™ technology that delivers industry-leading data  
throughput in mixed-speed USB environments, the USB251x family is a USB port-expansion  
solution for applications that demand low power and small footprint without compromising on  
performance.  
USB251x  
Additional information:  
www.smsc.com  
The MAX4899AE analog multiplexer combines the low on-capacitance (CON) and low on-  
resistance (RON) necessary for high-performance switching applications. This device is  
designed for USB 2.0 Hi-Speed applications at 480Mbps. The MAX4899AE also handles all  
the requirements for USB low- and full-speed signaling.  
MAX4899AE  
MAX3207  
Additional information:  
www.maxim-ic.com/MAX4899AE  
The MAX3207E is a low-capacitance, ±15kV ESD-protection diode array with an integrated  
TVS clamp. The device is suitable for high-speed and general-signal ESD protection. Low  
input capacitance makes this device ideal for ESD protection of signals in HDTV; PC  
monitors (DVI, HDMI); PC peripherals (FireWire, USB 2.0); server interconnect (PCI Express,  
Infiniband); datacom; and interchassis interconnect.  
Additional information:  
www.maxim-ic.com/MAX3207  
The MAX1558H is a dual, current-limited switch with autoreset that latches the switch off if it  
is shorted for more than 20ms, thus saving system power. The shorted output is then tested  
to determine when the short is removed so the channel can restart automatically. Each  
channel delivers up to 1.2A and meets all IEC specifications for USB ports. The MAX1558H  
safety features ensure that the USB port is protected.  
MAX1558H  
Additional information:  
www.maxim-ic.com/MAX1558H  
Reference Design HFRD-34.0 (Rev.3, 05/08)  
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Audio Section Components  
Part Number  
Functional Description  
The MAX4550 serial-interface, programmable, dual 4x2 audio/video crosspoint switch is ideal  
for multimedia applications. It contains two identical crosspoint switch arrays, each with four  
inputs and two outputs. To improve off-isolation, the additional crosspoint inputs, SA and SB,  
can be used as shunts. The output is selectively programmable for clickless or regular mode  
operation. A set of internal resistive voltage-dividers supplies DC bias for each output when  
using AC-coupled inputs. Additionally, four auxiliary outputs control additional circuitry  
through the MAX4550’s 2-wire interface.  
MAX4550  
Additional information:  
www.maxim-ic.com/MAX4550  
The MAX9728A stereo headphone amplifier is designed for display and notebook  
applications or portable equipment where board space is at a premium. This device uses a  
unique, patented DirectDrive™ architecture to produce a ground-referenced output from a  
single supply, thereby eliminating the need for large DC-blocking capacitors. It saves cost,  
board space, and component height. The MAX9728A offers an externally adjustable gain and  
delivers up to 60mW per channel into a 32Ω load with 0.02% THD+N. An 80dB at 1kHz  
power-supply rejection ratio (PSRR) allows these devices to operate from noisy digital  
supplies without an additional linear regulator. Comprehensive click-and-pop circuitry  
suppresses audible clicks and pops at startup and shutdown.  
MAX9728A  
Additional information:  
www.maxim-ic.com/MAX9728A  
The MAX9723 stereo DirectDrive™ headphone amplifier with BassMax and volume control is  
ideal for portable audio applications where space is at a premium and high performance is  
essential. The MAX9723 operates from a single 1.8V to 3.6V power supply. The device  
includes features that reduce external component count, system cost, and board space; other  
features improve audio reproduction. The headphone amplifier uses Maxim’s patented  
DirectDrive architecture that produces a ground-referenced output from a single supply,  
thereby eliminating the need for large DC-blocking capacitors.  
The headphone amplifiers deliver 62mW into a 16Ω load, feature low 0.006% THD+N, and  
high 90dB PSRR. The MAX9723 features Maxim’s industry-leading click-and-pop  
suppression. The BassMax feature boosts the amplifier’s bass response, thus improving  
audio reproduction when inexpensive headphones are used. The integrated volume control  
features 32 discrete volume levels, eliminating the need for an external potentiometer.  
BassMax and the volume control are enabled through the I2C/SMBus™-compatible interface.  
Shutdown is controlled through either the hardware or software interfaces.  
MAX9723  
Additional information:  
www.maxim-ic.com/MAX9723  
Reference Design HFRD-34.0 (Rev.3, 05/08)  
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Control, Power Management, and Miscellaneous Components  
Part Number  
Functional Description  
The ATMega48 is a low-power CMOS 8-bit microcontroller based on the AVR enhanced  
RISC architecture. By executing instructions in a single clock cycle, the ATMega48 achieves  
throughputs approaching 1 MIPS per MHz, allowing the system designer to optimize power  
consumption versus processing speed.  
The ATMega48 features a multiple-input 10-bit ADC, an 8-bit and a 16-bit timer with two  
PWM outputs each, an internal 8MHz oscillator, a 2-wire compatible interface, and a POR  
and brown-out circuit. The ATMega48 provides 4k flash, 256B of EEPROM, and 512B of  
SRAM.  
ATMEGA48  
Additional information:  
www.atmel.com  
The MAX7312 2-wire-interfaced expander provides 16-bit parallel input/output (I/O) port  
expansion in SMBus and I2C applications. The MAX7312 consists of input port registers,  
output port registers, polarity inversion registers, configuration registers, a bus timeout  
register, and an I2C-compatible serial interface logic, compatible with SMBus.  
MAX7312  
Additional information:  
www.maxim-ic.com/MAX7312  
The MAX3397E ±15kV ESD-protected, bidirectional level translator provides level shifting for  
data transfer in a multivoltage system. Externally applied voltages, VCC and VL, set the logic  
levels on either side of the device. A logic-low signal present on the VL side of the device  
appears as a logic-low signal on the VCC side of the device, and vice versa. The MAX3397E  
utilizes a transmission and gate-based design to allow data translation in either direction on  
any single data line.  
MAX3397E  
Additional information:  
www.maxim-ic.com/MAX3397E  
The MAX6348 microprocessor (ꢁP) supervisory circuit monitors the power supplies in ꢁP and  
digital systems. This device provides excellent circuit reliability and low cost by eliminating  
external components and adjustments when it is used with 2.5, 3, 3.3, and 5V powered  
circuits. The MAX6348 asserts a reset signal whenever the VCC supply voltage declines  
below a preset threshold; the device keeps the signal asserted for at least 100ms after VCC  
has risen above the reset threshold.  
MAX6348  
MAX1563  
Additional information:  
www.maxim-ic.com/MAX6348  
The MAX1563 single, current-limited switch provides up to 4A to power up to eight USB  
ports. It operates from a 4V to 5.5V input supply, and consumes only 40ꢁA of quiescent  
current when operating and only 3ꢁA in shutdown.  
Additional information:  
www.maxim-ic.com/MAX1563  
Reference Design HFRD-34.0 (Rev.3, 05/08)  
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MAX1853  
The MAX1853 monolithic, CMOS charge-pump voltage inverter in the ultra-small SC70  
package features a low 15Ω output resistance, which permits loads up to 30mA with  
maximum efficiency. The MAX1853 is available with an operating frequency of 200kHz,  
allowing optimization of supply current or external component size. Small external  
components and micropower shutdown mode make this device ideal for both battery-  
powered and board-level voltage conversion applications.  
Additional information:  
www.maxim-ic.com/MAX1853  
The MAX6817 dual switch debouncer provides clean interfacing of mechanical switches to  
digital systems. The device accepts one or more bouncing inputs from a mechanical switch  
and produces a clean digital output after a short, preset qualification delay. Both the switch  
opening and closing bounces are removed. Robust switch inputs handle ±25V levels and are  
±15kV ESD protected for use in harsh industrial environments. The MAX6817 features  
single-supply operation from +2.7V to +5.5V. Undervoltage lockout circuitry ensures that the  
output is in the correct state upon power-up. The MAX6817 is offered in a SOT package and  
requires no external components.  
MAX6817  
Additional information:  
www.maxim-ic.com/MAX6817  
The MAX1953/MAX1954/MAX1957 is a family of versatile, economical, synchronous current-  
mode, pulse-width modulation (PWM) buck controllers. These step-down controllers are  
targeted for applications where cost and size are critical. The MAX1953 operates at a fixed  
1MHz switching frequency, thus significantly reducing external component size and cost.  
Additionally, excellent transient response is obtained using less output capacitance. The  
MAX1953 operates from low 3V to 5.5V input voltage and can supply up to 10A of output  
current. Selectable current limit is provided to tailor to the external MOSFETs’ on-resistance  
for optimal cost and performance. The output voltage is adjustable from 0.8V to 0.86VIN.  
MAX1953  
MAX4070  
Additional information:  
www.maxim-ic.com/MAX1953  
The MAX4069–MAX4072 low-cost, bidirectional, high-side, current-sense amplifiers are ideal  
for monitoring battery charge and discharge currents in notebook PCs, cell phones, and other  
portable equipment. The devices feature up to 24V input common-mode voltage range, low  
100ꢁA supply current (which drops to only 10ꢁA in shutdown), and a total output error of less  
than 1.5%. The wide 1.35V to 24V input common-mode range is independent of the supply  
voltage, thus ensuring that the current-sense feedback remains accurate even when  
connected to a battery pack in deep discharge.  
Additional information:  
www.maxim-ic.com/MAX4070  
Reference Design HFRD-34.0 (Rev.3, 05/08)  
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The MAX3420E contains the digital logic and analog circuitry necessary to implement a full-  
speed USB peripheral compliant to USB specification rev 2.0. A built-in full-speed transceiver  
features ±15kV ESD protection and programmable USB connect and disconnect. An internal  
serial-interface engine (SIE) handles low-level USB protocol details such as error checking  
and bus retries. The MAX3420E operates using a register set accessed by an SPI™  
interface that operates up to 26MHz. Any SPI master (microprocessor, ASIC, DSP, etc.) can  
add USB functionality by using the simple 3- or 4-wire SPI interface.  
MAX3420  
MAX4788  
Additional information:  
www.maxim-ic.com/MAX3420  
The MAX4785–MAX4788 family of switches feature internal current limiting to prevent host  
devices from being damaged due to faulty load conditions. These analog switches have a low  
0.7Ω on-resistance and operate from a 2.3V to 5.5V input voltage range. They are available  
with guaranteed 50mA and 100mA current limits, making them ideal for load-switching  
applications.  
Additional information:  
www.maxim-ic.com/MAX4788  
7 Navigation Menu  
based interface, the user can set, save, and load  
configurations and control a variety of other  
features available in the reference design. The  
table below details the menu options available.  
HFRD-34.0 is controlled through an easy-to-use  
navigation switch (up, down, left, right, and push  
to select) and LCD display. Through this menu-  
Table 1. Navigation Menu Details  
Menu* Index LCD Label  
Action Taken by Pushing “Select” on Menu Item  
Configuration Menu (CM) is opened  
MM  
MM  
MM  
MM  
MM  
MM  
CM  
1
2
3
4
5
6
1
Configuration  
Video Switch  
Audio Switch  
USB Switch  
Video Switch Menu (VSM) is opened  
Audio Switch Menu (ASM) is opened  
USB Switch Menu (USM) is opened  
Audio Control Menu (ACM) is opened  
Advanced Control Menu (ADVM) is opened  
Audio Control  
Advanced Ctrl  
Load Config  
Opens a menu to allow the user to load one of four saved  
configurations.  
Opens menu to allow the user to save the current configuration to  
one of four memory locations. Saved configurations are retained  
during power cycles.  
CM  
2
Save Config  
Reference Design HFRD-34.0 (Rev.3, 05/08)  
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Sets the default configuration for the reference design  
(Audio/Video/USB In1 to Audio/Video/USB Out1;  
Audio/Video/USB In2 to Audio/Video/USB Out2, etc.)  
CM  
CM  
3
4
Default  
Puts the reference design into a demonstration mode. When in this  
mode, the controller will loop through the default and saved  
configurations at a preset time interval. This operation allows for  
automatic switching of the DVI and audio signals. Please note: The  
USB configuration is not switched in demo mode (only DVI and  
Audio).  
Demo Mode  
Return to Main Menu  
CM  
5
1
Main Menu  
DVI Out1  
Allows the user to switch DVI output 1 to any DVI input (1 through  
4). The current switch selection is highlighted.  
VSM  
Allows the user to switch DVI output 2 to any DVI input (1 through  
4). The current switch selection is highlighted.  
VSM  
VSM  
VSM  
2
3
4
DVI Out2  
DVI Out3  
DVI Out4  
Allows the user to switch DVI output 3 to any DVI input (1through  
4). The current switch selection is highlighted.  
Allows the user to switch DVI output 4 to any DVI input (1through  
4). The current switch selection is highlighted.  
Return to Main Menu  
VSM  
ASM  
5
1
Main Menu  
Allows the user to switch headphone output 1 to any audio input (1  
through 4). The current switch selection is highlighted.  
HeadphoneOut1  
Allows the user to switch headphone output 2 to any audio input (1  
through 4). The current switch selection is highlighted.  
ASM  
ASM  
ASM  
2
3
4
HeadphoneOut1  
Line Out1  
Allows the user to switch line output 1 to any audio input (1 through  
4). The current switch selection is highlighted.  
Allows the user to switch line output 2 to any audio input (1 through  
4). The current switch selection is highlighted.  
Line Out2  
Return to Main Menu  
ASM  
USM  
5
1
Main Menu  
Allows the user to switch USB hub 1 to any USB input (1 through  
4). The current switch selection is highlighted. Note: Fanout is not  
supported in the USB switch.  
USB HUB1 Out  
Allows the user to switch USB hub 2 to any USB input (1 through  
4). The current switch selection is highlighted. Note: Fanout is not  
supported in the USB switch.  
USM  
USM  
USM  
2
3
4
USB HUB2 Out  
USB HUB3 Out  
USB HUB4 Out  
Allows the user to switch USB hub 3 to any USB input (1 through  
4). The current switch selection is highlighted. Note: Fanout is not  
supported in the USB switch.  
Allows the user to switch USB hub 4 to any USB input (1through 4).  
The current switch selection is highlighted. Note: Fanout is not  
supported in the USB switch.  
Return to Main Menu  
USM  
ACM  
5
1
Main Menu  
HP1 Volume  
Allows the user to adjust headphone 1 output volume (1 through 7).  
Reference Design HFRD-34.0 (Rev.3, 05/08)  
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The current volume selection is highlighted.  
Allows the user to adjust headphone 2 output volume (1through 7).  
The current volume selection is highlighted.  
ACM  
2
HP2 Volume  
Return to Main Menu  
ACM  
3
1
Main Menu  
Allows the user to adjust DVI Out 1 preemphasis level between 0dB,  
3dB, and 6dB. The preemphasis can be increased to improve signal  
integrity when using long cables between HFRD-34.0 and the  
monitor.  
ADVM  
DVI1 Pre-Emph  
Allows the user to adjust DVI Out 2 preemphasis level between 0dB,  
3dB, and 6dB. The preemphasis can be increased to improve signal  
integrity when using long cables between HFRD-34.0 and the  
monitor.  
ADVM  
ADVM  
ADVM  
ADVM  
2
3
4
5
DVI2 Pre-Emph  
DVI3 Pre-Emph  
DVI4 Pre-Emph  
Main Menu  
Allows the user to adjust DVI Out 3 preemphasis level between 0dB,  
3dB, and 6dB. The preemphasis can be increased to improve signal  
integrity when using long cables between HFRD-34.0 and the  
monitor.  
Allows the user to adjust DVI Out 4 preemphasis level between 0dB,  
3dB, and 6dB. The preemphasis can be increased to improve signal  
integrity when using long cables between HFRD-34.0 and the  
monitor.  
Return to Main Menu  
*Abbreviations: MM: Main Menu; CM: Configuration Menu; VSM: Video Switch Menu; ASM: Audio  
Switch Menu; USM: USB Switch Menu; ACM: Audio Control Menu; ADVM: Advanced Control Menu.  
Reference Design HFRD-34.0 (Rev.3, 05/08)  
Maxim Integrated Products  
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these features and configurations are set  
through the ꢀC firmware.  
8 Schematics, Component List,  
and Layout Drawings  
3. The USB HUB reset connection for the  
four HUBs (pin 26 of USB2512 and  
USB2513 devices) are tied together on the  
current version of the reference design.  
Splitting these connections to have  
individual control will improve the  
overall USB switching operation.  
The full schematics, component list, and PCB  
layout drawings are available to download in PDF  
format at:  
http://www.maxim-  
ic.com/tools/other/appnotes/4232/4232_softwar  
e.zip.  
4. If desired, U47 (MAX3420) is provided  
to facilitate control of the switch through  
a USB interface. Currently these features  
are not preprogrammed into the reference  
design.  
See sections 10 and 11 for additional details  
regarding the use of the schematics and layout  
drawings for new designs.  
9 Gerber Files and Firmware  
5. USB HUB 4 is a self-powered HUB  
(power is drawn from the HFRD-34.0  
supply). USB HUBs 1-3 are powered  
from the host. All USB HUBs include  
overcurrent shutdown protection.  
The Gerber files and firmware assist design  
engineers in developing their projects, and are  
available to Maxim customers upon request. See  
sections 10 and 11 for additional details regarding  
the use of Gerber files and firmware. To receive  
the Gerber or firmware files, please send an email  
to [email protected] with HFRD-  
34.0 in the subject line. Include the following  
information:  
6. It is recommended that you increase the  
supply filtering (i.e., add series inductance  
and bulk capacitance) of the host USB  
power supplies (for HUBs 1-3) in order to  
reduce crosstalk from the USB power-  
supply noise to the audio outputs.  
1. Your name  
2. Company name  
3. Company website  
4. Brief description of your project  
7. The power MOSFET transistors (Q2-  
Q13) used for switching the USB host  
power are flipped over due to a layout  
error in the pin order. When copying this  
section of the design, the transistor  
footprint should be corrected.  
10 Design Notes  
Please review the following design notes:  
8. The ATMEL ꢀC (U49, ATMEGA168)  
can be in-circuit reprogrammed to  
perform custom features. Use the  
AVRISP-MKII programmer and the  
connections provided through J15.  
1. Line Out1 and Line Out2 are designed to  
drive an audio line impedance (> 1kΩ)  
with typical line-out voltage levels. These  
two audio outputs can be optimized to  
drive headphone loads by changing  
external component values. See the  
MAX9728 data sheet for additional  
information.  
9. A 10kΩ pull-up resistor should be added  
to pin 9 of the MAX3420 (U47) in any  
design revisions.  
2. The USB hub controllers (U26, U27,  
U36, and U39) have configurations and  
settings that can be adjusted through a 2-  
wire bus controlled by the ꢀC. Currently  
10. Connecting pins 14 and 16 together on  
each DVI input will increase the  
Reference Design HFRD-34.0 (Rev.3, 05/08)  
Maxim Integrated Products  
Page 15 of 18  
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compatibility of the reference design with  
a wider variety of DVI video cards.  
2. 0.5oz copper foil before platting.  
3. For USB signal-transmission lines: 10mil  
W, 8mil S -> 90Ω Differential  
4. For DVI signal-transmission lines: 8mil  
W, 8mil S -> 100Ω Differential  
11 Evaluation/Use Notes  
Table 2. HFRD-34.0 Layer Profile  
This reference design aids designers and is not  
intended to replace the entire design process. The  
designer should evaluate the reference design and  
modify it, as necessary, to meet the specification  
for a particular project. The designer should also  
carefully consider safety and EMI issues related to  
the specific application.  
Dielectric  
Thickness  
(inches)  
Copper  
Clad  
Layer  
Desc.  
Layer  
1
2
0.5  
0.5  
0.5  
0.5  
0.5  
0.5  
0.5  
0.5  
0.5  
0.5  
SIGNAL  
PLANE  
SIGNAL  
SIGNAL  
PLANE  
SIGNAL  
PLANE  
SIGNAL  
PLANE  
SIGNAL  
0.0081  
0.005  
Maxim cannot assume responsibility for use of  
any circuitry other than circuitry entirely  
embodied in a Maxim product. No circuit patent  
licenses are implied. Maxim reserves the right to  
change the circuitry and specifications without  
notice at any time.  
3
0.0036  
0.005  
4
5
0.0088  
0.005  
6
12 Layer Profile  
7
0.0036  
0.005  
The HFRD-34.0 DVI KVM switch includes  
controlled-impedance transmission lines. The  
layer profile is based on the following  
assumptions:  
8
9
0.0081  
1. Dielectric material is FR-4 with  
dielectric constant of ~ 4.2.  
a
10  
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim  
product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and  
specifications without notice at any time.  
Reference Design HFRD-34.0 (Rev.3, 05/08)  
Maxim Integrated Products  
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1312  
Board Dimensions  
Figure 8. HFRD-34.0 Board dimensions (not to scale).  
Reference Design HFRD-34.0 (Rev.3, 05/08)  
Maxim Integrated Products  
Page 17 of 18  
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DVI is a trademark of Digital Display Working Group (DDWG).  
FireWire is a registered trademark of Apple Computer, Inc.  
HDMI is a trademark of HDMI Licensing, LLC.  
InfiniBand is a registered trademark of InfiniBand Trade Association.  
MultiTRAK is a trademark of Standard Microsystems Corporation.  
PCI Express is a registered trademark of PCI-SIG Corp.  
SMBus is a trademark of Intel Corporation.  
SPI is a trademark of Motorola, Inc.  
TMDS is a registered trademark of Silicon Image, Inc.  
Reference Design HFRD-34.0 (Rev.3, 05/08)  
Maxim Integrated Products  
Page 18 of 18  
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