Cypress Clock CY7B991 User Manual

CY7B991  
CY7B992  
Programmable Skew Clock Buffer  
Features  
Functional Description  
All output pair skew <100 ps typical (250 maximum)  
3.75 to 80 MHz output operation  
The CY7B991 and CY7B992 Programmable Skew Clock Buffers  
(PSCB) offer user selectable control over system clock functions.  
These multiple output clock drivers provide the system integrator  
with functions necessary to optimize the timing of high perfor-  
mance computer systems. Each of the eight individual drivers,  
arranged in four pairs of user controllable outputs, can drive  
terminated transmission lines with impedances as low as 50Ω.  
They can deliver minimal and specified output skews and full  
swing logic levels (CY7B991 TTL or CY7B992 CMOS).  
User selectable output functions  
Selectable skew to 18 ns  
Inverted and non-inverted  
Operation at 12 and 14 input frequency  
Operation at 2x and 4x input frequency (input as low as 3.75  
MHz)  
Each output is hardwired to one of the nine delay or function  
configurations. Delay increments of 0.7 to 1.5 ns are determined  
by the operating frequency with outputs that skew up to ±6 time  
units from their nominal “zero” skew position. The completely  
integrated PLL allows cancellation of external load and trans-  
mission line delay effects. When this “zero delay” capability of the  
PSCB is combined with the selectable output skew functions,  
you can create output-to-output delays of up to ±12 time units.  
Zero input to output delay  
50% duty cycle outputs  
Outputs drive 50Ω terminated lines  
Low operating current  
32-pin PLCC/LCC package  
Jitter < 200 ps peak-to-peak (< 25 ps RMS)  
Divide-by-two and divide-by-four output functions are provided  
for additional flexibility in designing complex clock systems.  
When combined with the internal PLL, these divide functions  
enable distribution of a low frequency clock that are multiplied by  
two or four at the clock destination. This facility minimizes clock  
distribution difficulty, allowing maximum system clock speed and  
flexibility.  
Logic Block Diagram  
TEST  
PHASE  
FREQ  
DET  
FB  
VCO AND  
TIME UNIT  
GENERATOR  
FILTER  
REF  
FS  
4Q0  
4Q1  
4F0  
4F1  
SELECT  
INPUTS  
(THREE  
LEVEL)  
SKEW  
3Q0  
3F0  
3F1  
3Q1  
SELECT  
2Q0  
2F0  
2F1  
MATRIX  
2Q1  
1Q0  
1Q1  
1F0  
1F1  
Cypress Semiconductor Corporation  
Document Number: 38-07138 Rev. *B  
198 Champion Court  
San Jose, CA 95134-1709  
408-943-2600  
Revised June 22, 2007  
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CY7B991  
CY7B992  
Skew Select Matrix  
Block Diagram Description  
The skew select matrix contains four independent sections. Each  
section has two low skew, high fanout drivers (xQ0, xQ1), and  
two corresponding three level function select (xF0, xF1) inputs.  
Table 2 shows the nine possible output functions for each section  
as determined by the function select inputs. All times are  
measured with respect to the REF input assuming that the output  
Phase Frequency Detector and Filter  
The Phase Frequency Detector and Filter blocks accept inputs  
from the reference frequency (REF) input and the feedback (FB)  
input and generate correction information to control the  
frequency of the Voltage Controlled Oscillator (VCO). These  
blocks, along with the VCO, form a Phase Locked Loop (PLL)  
that tracks the incoming REF signal.  
connected to the FB input has 0t selected.  
U
Table 2. Programmable Skew Configurations  
VCO and Time Unit Generator  
Function Selects  
Output Functions  
The VCO accepts analog control inputs from the PLL filter block.  
It generates a frequency used by the time unit generator to  
create discrete time units that are selected in the skew select  
matrix. The operational range of the VCO is determined by the  
1F1,2F1, 1F0,2F0, 1Q0,1Q1,  
3F1, 4F1 3F0, 4F0 2Q0, 2Q1  
3Q0, 3Q1 4Q0, 4Q1  
LOW  
LOW  
LOW  
MID  
LOW  
MID  
–4t  
–3t  
–2t  
–1t  
Divide by 2 Divide by 2  
U
U
U
U
FS control pin. The time unit (t ) is determined by the operating  
–6t  
–4t  
–2t  
–6t  
–4t  
–2t  
U
U
U
U
U
U
U
frequency of the device and the level of the FS pin as shown in  
HIGH  
LOW  
MID  
[1]  
Table 1. Frequency Range Select and t Calculation  
U
MID  
0t  
0t  
0t  
U
U
U
f
(MHz)  
NOM  
MID  
HIGH  
LOW  
MID  
+1t  
+2t  
+3t  
+4t  
+2t  
+4t  
+6t  
+2t  
+4t  
+6t  
1
Approximate  
U
U
U
U
U
U
U
U
U
U
tU = -----------------------  
[2, 3]  
FS  
Frequency(MHz)At  
fNOM × N  
HIGH  
HIGH  
HIGH  
Min Max  
Which t = 1.0 ns  
U
where N =  
LOW  
MID  
15  
25  
40  
30  
50  
80  
44  
26  
16  
22.7  
38.5  
62.5  
HIGH  
Divide by 4 Inverted  
HIGH  
Notes  
1. For all tri-state inputs, HIGH indicates a connection to VCC, LOW indicates a connection to GND, and MID indicates an open connection. Internal termination circuitry  
holds an unconnected input to VCC/2.  
2. The level is set on FS is determined by the “normal” operating frequency (fNOM) of the VCO and Time Unit Generator (see Logic Block Diagram). Nominal frequency  
(fNOM) always appears at 1Q0 and the other outputs when they are operated in their undivided modes (see Table 2). The frequency appearing at the REF and FB  
inputs are fNOM when the output connected to FB is undivided. The frequency of the REF and FB inputs are fNOM/2 or fNOM/4 when the part is configured for a  
frequency multiplication by using a divided output as the FB input.  
3. When the FS pin is selected HIGH, the REF input must not transition upon power up until VCC has reached 4.3V.  
Document Number: 38-07138 Rev. *B  
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CY7B991  
CY7B992  
Figure 1 shows the typical outputs with FB connected to a zero skew output.  
Figure 1. Typical Outputs with FB Connected to a Zero-Skew Output  
FBInput  
REFInput  
1Fx  
2Fx  
3Fx  
4Fx  
(N/A)  
LM  
– 6t  
– 4t  
– 3t  
U
U
U
LL  
LH  
LM  
(N/A)  
LH  
ML  
ML  
– 2t  
– 1t  
U
U
(N/A)  
MM  
MH  
HL  
MM  
(N/A)  
MH  
0t  
U
U
U
U
+1t  
+2t  
+3t  
HM  
(N/A)  
HH  
HL  
HM  
+4t  
+6t  
U
U
(N/A)  
(N/A)  
(N/A)  
LL/HH  
HH  
DIVIDED  
INVERT  
Test Mode  
The TEST input is a three level input. In normal system  
operation, this pin is connected to ground, enabling the  
CY7B991 or CY7B992 to operate as explained in “Skew Select  
Matrix” on page 3. For testing purposes, any of the three level  
inputs can have a removable jumper to ground, or be tied LOW  
through a 100Ω resistor. This enables an external tester to  
change the state of these pins.  
If the TEST input is forced to its MID or HIGH state, the device  
operates with its internal phase locked loop disconnected, and  
input levels supplied to REF directly controls all outputs. Relative  
output to output functions are the same as in normal mode.  
In contrast with normal operation (TEST tied LOW), all outputs  
function based only on the connection of their own function  
selects inputs (xF0 and xF1) and the waveform characteristics of  
the REF input.  
Note  
4. FB connected to an output selected for “zero” skew (i.e., xF1 = xF0 = MID).  
Document Number: 38-07138 Rev. *B  
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CY7B991  
CY7B992  
Maximum Ratings  
Operating Range  
Operating outside these boundaries affects the performance and  
life of the device. These user guidelines are not tested.  
Ambient  
Temperature  
Range  
V
CC  
Storage Temperature .................................65°C to +150°C  
Ambient Temperature with  
Power Applied ............................................55°C to +125°C  
Supply Voltage to Ground Potential................–0.5V to +7.0V  
DC Input Voltage ............................................–0.5V to +7.0V  
Output Current into Outputs (LOW)............................. 64 mA  
Commercial  
0°C to +70°C  
5V ± 10%  
5V ± 10%  
5V ± 10%  
5V ± 10%  
Industrial  
–40°C to +85°C  
–55°C to +125°C  
–55°C to +125°C  
[5]  
Military  
[5]  
Military  
Static Discharge Voltage............................................>2001V  
(MIL-STD-883, Method 3015)  
Latch Up Current .....................................................>200 mA  
Note  
5. Indicates case temperature.  
Document Number: 38-07138 Rev. *B  
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CY7B991  
CY7B992  
Electrical Characteristics  
Over the Operating Range  
CY7B991  
CY7B992  
Min Max  
Parameter  
Description  
Test Conditions  
= Min I = –16 mA  
Min  
Max  
Unit  
V
Output HIGH Voltage  
V
V
V
V
2.4  
V
OH  
CC  
CC  
CC  
CC  
OH  
= Min, I =–40 mA  
V
–0.75  
OH  
CC  
V
Output LOW Voltage  
= Min, I = 46 mA  
0.45  
V
OL  
OL  
= Min, I = 46 mA  
0.45  
OL  
V
V
V
V
V
I
Input HIGH Voltage  
(REF and FB inputs only)  
2.0  
V
V
1.35  
V
CC  
V
V
IH  
CC  
CC  
Input LOW Voltage  
(REF and FB inputs only)  
–0.5  
0.8  
–0.5  
1.35  
IL  
Three Level Input HIGH  
Voltage (Test, FS, xFn)  
Min V Max  
V
– 0.85  
V
V
– 0.85  
V
V
IHH  
IMM  
ILL  
CC  
CC  
CC  
CC  
CC  
Three Level Input MID  
Voltage (Test, FS, xFn)  
Min V Max  
V
/2 –  
V
/2 +  
V
/2 –  
V /2 +  
CC  
500 mV  
V
CC  
CC  
CC  
500 mV  
CC  
500 mV  
500 mV  
Three Level Input LOW  
Voltage (Test, FS, xFn)  
Min V  
0.0  
0.85  
0.0  
0.85  
V
CC  
Maximum  
InputHIGHLeakageCurrent  
(REF and FB inputs only)  
V
V
V
V
V
V
= Max, V = Max.  
10  
10  
μA  
μA  
μA  
μA  
μA  
mA  
mA  
IH  
CC  
CC  
IN  
IN  
I
I
I
I
I
I
Input LOW Leakage Current  
(REF and FB inputs only)  
= Max, V = 0.4V  
–500  
–50  
–500  
–50  
IL  
IN  
Input HIGH Current  
(Test, FS, xFn)  
= V  
200  
50  
200  
50  
IHH  
IMM  
ILL  
CC  
Input MID Current  
(Test, FS, xFn)  
= V /2  
IN  
CC  
Input LOW Current  
(Test, FS, xFn)  
= GND  
–200  
–250  
–200  
N/A  
IN  
Output Short Circuit  
= Max, V  
OUT  
OS  
CC  
Current  
= GND (25°C only)  
Operating Current Used by  
Internal Circuitry  
V
=V  
=Max, Com’l  
85  
90  
85  
90  
CCQ  
CCN  
CCQ  
All Input  
Selects Open  
Mil/Ind  
I
Output Buffer Current per  
Output Pair  
V
= V = Max,  
CCQ  
= 0 mA  
14  
19  
mA  
CCN  
CCN  
I
OUT  
Input Selects Open, f  
MAX  
PD  
Power Dissipation per  
Output Pair  
V
= V  
= 0 mA  
= Max,  
78  
mW  
CCN  
CCQ  
I
OUT  
Input Selects Open, f  
MAX  
Notes  
6. For more information see “Group A Subgroup Testing” on page 17.  
7. These inputs are normally wired to V , GND, or left unconnected (actual threshold voltages vary as a percentage of V ). Internal termination resistors hold  
CC  
CC  
unconnected inputs at V /2. If these inputs are switched, the function and timing of the outputs may glitch and the PLL may require an additional t  
CC  
time before  
LOCK  
all datasheet limits are achieved.  
8. CY7B991 must be tested one output at a time, output shorted for less than one second, less than 10% duty cycle. Room temperature only. CY7B992 outputs must  
not be shorted to GND. Doing so may cause permanent damage.  
9. Total output current per output pairis approximated by the following expression that includes device current plus load current:  
CY7B991:  
CY7B992:  
Where  
I
I
= [(4 + 0.11F) + [((835 – 3F)/Z) + (.0022FC)]N] x 1.1  
= [(3.5+ 0.17F) + [((1160 – 2.8F)/Z) + (.0025FC)]N] x 1.1  
CCN  
CCN  
F = frequency in MHz; C = capacitive load in pF; Z = line impedance in ohms; N = number of loaded outputs; 0, 1, or 2; FC = F < C.  
10. Total power dissipation per output pair can be approximated by the following expression that includes device power dissipation plus power dissipation due to the load  
circuit:  
CY7B991:PD = [(22 + 0.61F) + [((1550 – 2.7F)/Z) + (.0125FC)]N] x 1.1  
CY7B992:PD = [(19.25+ 0.94F) + [((700 + 6F)/Z) + (.017FC)]N] x 1.1  
See note 9 for variable definition.  
11. Applies to REF and FB inputs only. Tested initially and after any design or process changes that may affect these parameters.  
Document Number: 38-07138 Rev. *B  
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CY7B991  
CY7B992  
Capacitance  
CMOS output buffer current and power dissipation specified at 50 MHz reference frequency.  
Parameter  
Description  
Test Conditions  
Max  
Unit  
C
Input Capacitance  
T = 25°C, f = 1 MHz, V = 5.0V  
10  
pF  
IN  
A
CC  
AC Test Loads and Waveforms  
5V  
3.0V  
2.0V  
=1.5V  
0.8V  
0.0V  
2.0V  
=1.5V  
0.8V  
R1=130  
R2=91  
R1  
R2  
V
th  
V
th  
C = 50 pF (C =30 pF for –2 and –5 devices)  
L
L
C
L
(Includes fixture and probe capacitance)  
1ns  
1ns  
TTL ACTest Load (CY7B991)  
TTL Input Test Waveform (CY7B991)  
V
CC  
V
CC  
R1=100  
R2=100  
80%  
CC  
20%  
0.0V  
80%  
= V /2  
20%  
R1  
=30 pF for –2 and –5 devices)  
C = 50 pF (C  
L
L
V
th  
= V /2  
V
th  
CC  
(Includes fixture and probe capacitance)  
C
L
R2  
3ns  
3ns  
CMOS AC Test Load (CY7B992)  
CMOS Input Test Waveform (CY7B992)  
Document Number: 38-07138 Rev. *B  
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CY7B991  
CY7B992  
Switching Characteristics Over the Operating Range  
CY7B991–2  
CY7B992–2  
Parameter  
Description  
FS = LOW  
Min  
15  
Typ  
Max  
Min  
Typ  
Max  
Unit  
f
Operating Clock  
30  
50  
80  
15  
30  
50  
MHz  
NOM  
Frequency in MHz  
FS = MID  
25  
40  
25  
40  
FS = HIGH  
80  
t
t
t
t
REF Pulse Width HIGH  
REF Pulse Width LOW  
Programmable Skew Unit  
5.0  
5.0  
5.0  
ns  
ns  
RPWH  
RPWL  
U
5.0  
Zero Output Matched-Pair Skew  
0.05  
0.20  
0.05  
0.20  
ns  
SKEWPR  
(XQ0, XQ1)  
t
t
Zero Output Skew (All Outputs)  
0.1  
0.25  
0.5  
0.1  
0.25  
0.5  
ns  
ns  
SKEW0  
SKEW1  
Output Skew (Rise-Rise, Fall-Fall, Same  
0.25  
0.25  
Class Outputs)  
t
t
t
Output Skew (Rise-Fall, Nominal-Inverted,  
Divided-Divided)  
0.3  
0.25  
0.5  
0.5  
0.5  
0.9  
0.3  
0.25  
0.5  
0.5  
0.5  
0.7  
ns  
ns  
ns  
SKEW2  
SKEW3  
SKEW4  
Output Skew (Rise-Rise, Fall-Fall, Different  
Class Outputs)  
Output Skew (Rise-Fall, Nominal-Divided,  
Divided-Inverted)  
t
t
t
t
t
t
t
t
t
Device-to-Device Skew  
0.75  
+0.25  
+0.65  
2.0  
0.75  
+0.25  
+0.5  
3.0  
ns  
ns  
ns  
ns  
ns  
ns  
ns  
ms  
ps  
ps  
DEV  
Propagation Delay, REF Rise to FB Rise  
–0.25  
–0.65  
0.0  
0.0  
–0.25  
–0.5  
0.0  
0.0  
PD  
Output Duty Cycle Variation  
ODCV  
PWH  
PWL  
ORISE  
OFALL  
LOCK  
JR  
Output HIGH Time Deviation from 50%  
Output LOW Time Deviation from 50%  
1.5  
3.0  
Output Rise Time  
0.15  
0.15  
1.0  
1.0  
1.2  
0.5  
0.5  
2.0  
2.0  
2.5  
Output Fall Time  
1.2  
2.5  
PLL Lock Time  
0.5  
0.5  
Cycle-to-Cycle Output  
Jitter  
RMS  
25  
25  
Peak-to-Peak  
200  
200  
Notes  
12. CMOS output buffer current and power dissipation specified at 50 MHz reference frequency.  
13. Test measurement levels for the CY7B991 are TTL levels (1.5V to 1.5V). Test measurement levels for the CY7B992 are CMOS levels (VCC/2 to VCC/2). Test  
conditions assume signal transition times of 2 ns or less and output loading as shown in the AC Test Loads and Waveforms unless otherwise specified.  
14. Guaranteed by statistical correlation. Tested initially and after any design or process changes that affect these parameters.  
15. Except as noted, all CY7B992–2 and –5 timing parameters are specified to 80 MHz with a 30 pF load.  
16. SKEW is defined as the time between the earliest and the latest output transition among all outputs for which the same tU delay is selected when all are loaded  
with 50 pF and terminated with 50Ω to 2.06V (CY7B991) or VCC/2 (CY7B992).  
17. tSKEWPR is defined as the skew between a pair of outputs (XQ0 and XQ1) when all eight outputs are selected for 0tU.  
18. tSKEW0 is defined as the skew between outputs when they are selected for 0tU. Other outputs are divided or inverted but not shifted.  
19. CL=0 pF. For CL=30 pF, tSKEW0=0.35 ns.  
20. There are three classes of outputs: Nominal (multiple of tU delay), Inverted (4Q0 and 4Q1 only with 4F0 = 4F1 = HIGH), and Divided (3Qx and 4Qx only in  
Divide-by-2 or Divide-by-4 mode).  
21. tDEV is the output-to-output skew between any two devices operating under the same conditions (VCC ambient temperature, air flow, and so on.)  
22. tODCV is the deviation of the output from a 50% duty cycle. Output pulse width variations are included in tSKEW2 and tSKEW4 specifications.  
23. Specified with outputs loaded with 30 pF for the CY7B99X–2 and –5 devices and 50 pF for the CY7B99X–7 devices. Devices are terminated through 50Ω to  
2.06V (CY7B991) or VCC/2 (CY7B992).  
24. tPWH is measured at 2.0V for the CY7B991 and 0.8 VCC for the CY7B992. tPWL is measured at 0.8V for the CY7B991 and 0.2 VCC for the CY7B992.  
25. tORISE and tOFALL measured between 0.8V and 2.0V for the CY7B991 or 0.8VCC and 0.2VCC for the CY7B992.  
26. tLOCK is the time that is required before synchronization is achieved. This specification is valid only after VCC is stable and within normal operating limits.  
This parameter is measured from the application of a new signal or frequency at REF or FB until tPD is within specified limits.  
Document Number: 38-07138 Rev. *B  
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CY7B991  
CY7B992  
Switching Characteristics  
Over the Operating Range  
(continued)  
CY7B991–5  
Typ  
CY7B992–5  
Typ  
Parameter  
Description  
FS = LOW  
Min  
15  
Max  
30  
Min  
15  
Max  
30  
Unit  
[1, 2]  
f
Operating Clock  
MHz  
NOM  
Frequency in MHz  
[1, 2]  
FS = MID  
25  
50  
25  
50  
FS = HIGH  
40  
80  
40  
80  
t
t
t
t
REF Pulse Width HIGH  
REF Pulse Width LOW  
Programmable Skew Unit  
5.0  
5.0  
5.0  
5.0  
ns  
ns  
RPWH  
RPWL  
U
Zero Output Matched-Pair Skew  
0.1  
0.25  
0.1  
0.25  
ns  
SKEWPR  
(XQ0, XQ1)  
t
t
Zero Output Skew (All Outputs)  
0.25  
0.6  
0.5  
0.7  
0.25  
0.6  
0.5  
0.7  
ns  
ns  
SKEW0  
SKEW1  
Output Skew (Rise-Rise, Fall-Fall, Same  
Class Outputs)  
t
t
t
Output Skew (Rise-Fall, Nominal-Inverted,  
Divided-Divided)  
0.5  
0.5  
0.5  
1.0  
0.7  
1.0  
0.6  
0.5  
0.6  
1.5  
0.7  
1.7  
ns  
ns  
ns  
SKEW2  
SKEW3  
SKEW4  
Output Skew (Rise-Rise, Fall-Fall, Different  
Class Outputs)  
Output Skew (Rise-Fall, Nominal-Divided,  
Divided-Inverted)  
t
t
t
t
t
t
t
t
t
Device-to-Device Skew  
1.25  
+0.5  
+1.0  
2.5  
3
1.25  
+0.5  
+1.2  
4.0  
ns  
ns  
ns  
ns  
ns  
ns  
ns  
ms  
ps  
ps  
DEV  
Propagation Delay, REF Rise to FB Rise  
–0.5  
–1.0  
0.0  
0.0  
–0.5  
–1.2  
0.0  
0.0  
PD  
Output Duty Cycle Variation  
ODCV  
PWH  
PWL  
ORISE  
OFALL  
LOCK  
JR  
Output HIGH Time Deviation from 50%  
Output LOW Time Deviation from 50%  
4.0  
Output Rise Time  
0.15  
0.15  
1.0  
1.0  
1.5  
1.5  
0.5  
25  
0.5  
0.5  
2.0  
2.0  
3.5  
Output Fall Time  
3.5  
PLL Lock Time  
0.5  
Cycle-to-Cycle Output  
Jitter  
RMS  
25  
[14]  
Peak-to-Peak  
200  
200  
Document Number: 38-07138 Rev. *B  
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CY7B991  
CY7B992  
Switching Characteristics  
Over the Operating Range  
(continued)  
CY7B991–7  
Typ  
CY7B992–7  
Typ  
Parameter  
Description  
Operating Clock FS = LOW  
Min  
15  
Max  
30  
Min  
15  
Max  
30  
Unit  
f
MHz  
NOM  
Frequency in MHz  
FS = MID  
25  
50  
25  
50  
FS = HIGH  
40  
80  
40  
80  
t
t
t
t
REF Pulse Width HIGH  
REF Pulse Width LOW  
Programmable Skew Unit  
5.0  
5.0  
5.0  
5.0  
ns  
ns  
RPWH  
RPWL  
U
Zero Output Matched-Pair Skew  
0.1  
0.25  
0.1  
0.25  
ns  
SKEWPR  
(XQ0, XQ1)  
t
t
Zero Output Skew (All Outputs)  
0.3  
0.6  
0.75  
1.0  
0.3  
0.6  
0.75  
1.0  
ns  
ns  
SKEW0  
SKEW1  
Output Skew (Rise-Rise, Fall-Fall, Same  
Class Outputs)  
t
t
t
Output Skew (Rise-Fall, Nominal-Inverted,  
Divided-Divided)  
1.0  
0.7  
1.2  
1.5  
1.2  
1.7  
1.0  
0.7  
1.2  
1.5  
1.2  
1.7  
ns  
ns  
ns  
SKEW2  
SKEW3  
SKEW4  
Output Skew (Rise-Rise, Fall-Fall, Different  
Class Outputs)  
Output Skew (Rise-Fall, Nominal-Divided,  
Divided-Inverted)  
t
t
t
t
t
t
t
t
t
Device-to-Device Skew  
1.65  
+0.7  
+1.2  
3
1.65  
+0.7  
+1.5  
5.5  
ns  
ns  
ns  
ns  
ns  
ns  
ns  
ms  
ps  
ps  
DEV  
Propagation Delay, REF Rise to FB Rise  
–0.7  
–1.2  
0.0  
0.0  
–0.7  
–1.5  
0.0  
0.0  
PD  
Output Duty Cycle Variation  
ODCV  
PWH  
PWL  
ORISE  
OFALL  
LOCK  
JR  
Output HIGH Time Deviation from 50%  
[23, 24]  
Output LOW Time Deviation from 50%  
3.5  
2.5  
2.5  
0.5  
25  
5.5  
[23, 25]  
Output Rise Time  
0.15  
0.15  
1.5  
1.5  
0.5  
0.5  
3.0  
3.0  
5.0  
[23, 25]  
Output Fall Time  
5.0  
PLL Lock Time  
0.5  
Cycle-to-Cycle Output  
Jitter  
RMS  
25  
Peak-to-Peak  
200  
200  
Document Number: 38-07138 Rev. *B  
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CY7B991  
CY7B992  
AC Timing Diagrams  
t
t
RPWL  
REF  
t
RPWH  
REF  
t
t
ODCV  
PD  
t
ODCV  
FB  
Q
t
JR  
t
t
t
t
SKEWPR,  
SKEW0,1  
SKEWPR,  
SKEW0,1  
OTHERQ  
t
SKEW2  
t
SKEW2  
INVERTED Q  
t
SKEW3,4  
t
t
SKEW3,4  
t
SKEW3,4  
REF DIVIDED BY 2  
REF DIVIDED BY 4  
t
SKEW1,3, 4  
SKEW2,4  
Document Number: 38-07138 Rev. *B  
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CY7B991  
CY7B992  
Operational Mode Descriptions  
Figure 2. Zero Skew and Zero Delay Clock Driver  
REF  
LOAD  
Z
Z
0
L1  
L2  
FB  
SYSTEM  
CLOCK  
REF  
FS  
LOAD  
LOAD  
4Q0  
4Q1  
4F0  
4F1  
0
3Q0  
3Q1  
3F0  
3F1  
L3  
L4  
2F0  
2F1  
2Q0  
2Q1  
Z
0
1F0  
1F1  
1Q0  
1Q1  
LOAD  
TEST  
Z
0
LENGTH L1 = L2 = L3 = L4  
Figure 2 shows the PSCB configured as a zero skew clock buffer. In this mode the 7B991/992 is used as the basis for a low-skew  
clock distribution tree. When all of the function select inputs (xF0, xF1) are left open, the outputs are aligned and each drives a  
terminated transmission line to an independent load. The FB input is tied to any output in this configuration and the operating frequency  
range is selected with the FS pin. The low-skew specification, coupled with the ability to drive terminated transmission lines (with  
impedances as low as 50 ohms), enables efficient printed circuit board design.  
Figure 3. Programmable Skew Clock Driver  
REF  
LOAD  
Z
0
L1  
L2  
FB  
REF  
FS  
SYSTEM  
CLOCK  
LOAD  
LOAD  
4Q0  
4Q1  
4F0  
4F1  
Z
0
3Q0  
3Q1  
3F0  
3F1  
L3  
L4  
2F0  
2F1  
2Q0  
2Q1  
Z
0
1F0  
1F1  
1Q0  
1Q1  
LOAD  
TEST  
Z
0
LENGTH L1 = L2  
L3 < L2 by 6 inches  
L4 > L2 by 6 inches  
Figure 3 shows a configuration to equalize skew between metal  
traces of different lengths. In addition to low skew between  
outputs, the PSCB is programmed to stagger the timing of its  
outputs. Each of the four groups of output pairs are programmed  
to different output timing. Skew timing is adjusted over a wide  
range in small increments with the appropriate strapping of the  
function select pins. In this configuration the 4Q0 output is fed  
back to FB and configured for zero skew. The other three pairs  
of outputs are programmed to yield different skews relative to the  
feedback. By advancing the clock signal on the longer traces or  
retarding the clock signal on shorter traces, all loads can receive  
the clock pulse at the same time.  
In this illustration the FB input is connected to an output with 0-ns  
skew (xF1, xF0 = MID) selected. The internal PLL synchronizes  
Document Number: 38-07138 Rev. *B  
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CY7B991  
CY7B992  
F
the FB and REF inputs and aligns their rising edges to ensure  
that all outputs have precise phase alignment.  
Figure 5. Frequency Multiplier with Skew Connectrions  
Clock skews are advanced by ±6 time units (tU) when using an  
output selected for zero skew as the feedback. A wider range of  
delays is possible if the output connected to FB is also skewed.  
Since “Zero Skew”, +tU, and –tU are defined relative to output  
groups, and since the PLL aligns the rising edges of REF and  
FB, you can create wider output skews by proper selection of the  
xFn inputs. For example, a +10 tU between REF and 3Qx is  
achieved by connecting 1Q0 to FB and setting 1F0 = 1F1 = GND,  
3F0 = MID, and 3F1 = High. (Since FB aligns at –4 tU and 3Qx  
skews to +6 tU, a total of +10 tU skew is realized.) Many other  
configurations are realized by skewing both the outputs used as  
the FB input and skewing the other outputs.  
REF  
FB  
20 MHz  
REF  
FS  
40 MHz  
4Q0  
4Q1  
4F0  
4F1  
20 MHz  
80 MHz  
3Q0  
3Q1  
3F0  
3F1  
2F0  
2F1  
2Q0  
2Q1  
1Q0  
1Q1  
1F0  
1F1  
Figure 4. Inverted Output Connections  
TEST  
REF  
Figure 5 shows the PSCB configured as a clock multiplier. The  
3Q0 output is programmed to divide by four and is sent to FB.  
This causes the PLL to increase its frequency until the 3Q0 and  
3Q1 outputs are locked at 20 MHz while the 1Qx and 2Qx  
outputs run at 80 MHz. The 4Q0 and 4Q1 outputs are  
programmed to divide by two, that results in a 40 MHz waveform  
at these outputs. Note that the 20 and 40 MHz clocks fall simul-  
taneously and are out of phase on their rising edge. This enables  
FB  
REF  
FS  
4Q0  
4Q1  
4F0  
4F1  
1
1
the designer to use the rising edges of the frequency and ⁄  
2
4
3Q0  
3Q1  
3F0  
3F1  
frequency outputs without concern for rising edge skew. The  
2Q0, 2Q1, 1Q0, and 1Q1 outputs run at 80 MHz and are skewed  
by programming their select inputs accordingly. Note that the FS  
pin is wired for 80 MHz operation because that is the frequency  
of the fastest output.  
2Q0  
2Q1  
2F0  
2F1  
1Q0  
1Q1  
1F0  
1F1  
TEST  
Figure 6. Frequency Divider Connections  
REF  
Figure 4 shows an example of the invert function of the PSCB.  
In this example the 4Q0 output used as the FB input is  
programmed for invert (4F0 = 4F1 = HIGH) while the other three  
pairs of outputs are programmed for zero skew. When 4F0 and  
4F1 are tied high, 4Q0 and 4Q1 become inverted zero phase  
outputs. The PLL aligns the rising edge of the FB input with the  
rising edge of the REF. This causes the 1Q, 2Q, and 3Q outputs  
to become the “inverted” outputs with respect to the REF input.  
It is possible to have 2 inverted and 6 non-inverted outputs or 6  
inverted and 2 non-inverted outputs by selecting the output  
connected to FB. The correct configuration is determined by the  
need for more (or fewer) inverted outputs. 1Q, 2Q, and 3Q  
outputs can also be skewed to compensate for varying trace  
delays independent of inversion on 4Q.  
FB  
REF  
FS  
20 MHz  
10 MHz  
4Q0  
4F0  
4Q1  
4F1  
5 MHz  
3Q0  
3Q1  
3F0  
3F1  
20 MHz  
2Q0  
2Q1  
2F0  
2F1  
1F0  
1F1  
1Q0  
1Q1  
TEST  
Figure 6 demonstrates the PSCB in a clock divider application.  
2Q0 is fed back to the FB input and programmed for zero skew.  
3Qx is programmed to divide by four. 4Qx is programmed to  
divide by two. Note that the falling edges of the 4Qx and 3Qx  
outputs are aligned. This enables the use of rising edges of the  
1
1
frequency and  
frequency without concern for skew  
2
4
mismatch. The 1Qx outputs are programmed to zero skew and  
are aligned with the 2Qx outputs. In this example, the FS input  
is grounded to configure the device in the 15 MHz to 30 MHz  
Document Number: 38-07138 Rev. *B  
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CY7B991  
CY7B992  
range since the highest frequency output is running at 20 MHz.  
Figure 7 shows some of the functions that are selectable on the  
3Qx and 4Qx outputs. These include inverted outputs and  
outputs that offer divide-by-2 and divide-by-4 timing. An inverted  
output enables the system designer to clock different  
subsystems on opposite edges, without suffering from the pulse  
asymmetry typical of non-ideal loading. This function enables  
each of the two subsystems to clock 180 degrees out of phase  
and align within the skew specifications.  
of the divider adds to the skew between the different clock  
signals.  
These divided outputs, coupled with the Phase Locked Loop,  
enables the PSCB to multiply the clock rate at the REF input by  
either two or four. This mode enables the designer to distribute  
a low frequency clock between various portions of the system,  
and then locally multiply the clock rate to a more suitable  
frequency, still maintaining the low skew characteristics of the  
clock driver. The PSCB performs all of the functions described in  
this section at the same time. It multiplies by two and four or  
divides by two (and four) at the same time. In other words, it is  
shifting its outputs over a wide range or maintaining zero skew  
between selected outputs.  
The divided outputs offer a zero delay divider for portions of the  
system that need the clock divided by either two or four, and still  
remain within a narrow skew of the “1X” clock. Without this  
feature, an external divider is added, and the propagation delay  
Figure 7. Multi-Function Clock Driver  
REF  
LOAD  
Z
0
80 MHz  
INVERTED  
FB  
REF  
FS  
20 MHz  
DISTRIBUTION  
CLOCK  
LOAD  
LOAD  
4Q0  
4Q1  
4F0  
4F1  
20 MHz  
Z
0
3Q0  
3Q1  
2Q0  
2Q1  
3F0  
3F1  
2F0  
2F1  
80 MHz  
ZERO SKEW  
Z
0
1Q0  
1Q1  
1F0  
LOAD  
80 MHz  
SKEWED –3.125 ns (–4tU)  
1F1  
TEST  
Z
0
Document Number: 38-07138 Rev. *B  
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CY7B991  
CY7B992  
Figure 8. Board-to-Board Clock Distribution  
LOAD  
LOAD  
REF  
Z
0
L1  
FB  
SYSTEM  
CLOCK  
REF  
FS  
4F0  
4F1  
L2  
Z
0
4Q0  
4Q1  
3Q0  
3Q1  
3F0  
3F1  
LOAD  
L3  
2F0  
2F1  
2Q0  
2Q1  
Z
0
1F0  
1F1  
1Q0  
1Q1  
L4  
FB  
REF  
TEST  
FS  
LOAD  
4Q0  
4Q1  
3Q0  
3Q1  
2Q0  
2Q1  
1Q0  
1Q1  
4F0  
4F1  
3F0  
3F1  
2F0  
2F1  
1F0  
1F1  
TEST  
Z
0
LOAD  
Figure 8 shows the CY7B991 and 992 connected in series to construct a zero skew clock distribution tree between boards. Delays  
of the downstream clock buffers are programmed to compensate for the wire length (that is, select negative skew equal to the wire  
delay) necessary to connect them to the master clock source, approximating a zero delay clock tree. Cascaded clock buffers accumu-  
lates low frequency jitter because of the non-ideal filtering characteristics of the PLL filter. Do not connect more than two clock buffers  
in series.  
Document Number: 38-07138 Rev. *B  
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CY7B991  
CY7B992  
Ordering Information  
Accuracy  
Ordering Code  
(ps)  
Operating  
Range  
Package Type  
32-Pb Plastic Leaded Chip Carrier  
250  
CY7B991–2JC  
CY7B991–2JCT  
CY7B991–5JC  
CY7B991–5JCT  
CY7B991–5JI  
Commercial  
32-Pb Plastic Leaded Chip Carrier - Tape and Reel  
32-Pb Plastic Leaded Chip Carrier  
Commercial  
Commercial  
Commercial  
Industrial  
500  
32-Pb Plastic Leaded Chip Carrier - Tape and Reel  
32-Pb Plastic Leaded Chip Carrier  
CY7B991–5JIT  
CY7B991–7JC  
CY7B991–7JCT  
CY7B991–7JI  
32-Pb Plastic Leaded Chip Carrier - Tape and Reel  
32-Pb Plastic Leaded Chip Carrier  
Industrial  
750  
Commercial  
Commercial  
Industrial  
32-Pb Plastic Leaded Chip Carrier - Tape and Reel  
32-Pb Plastic Leaded Chip Carrier  
CY7B991–7LMB  
CY7B992–2JC  
CY7B992–2JCT  
CY7B992–5JC  
CY7B992–5JCT  
32-Pin Rectangular Leadless Chip Carrier  
32-Pb Plastic Leaded Chip Carrier  
Military  
250  
500  
Commercial  
Commercial  
Commercial  
Commercial  
Industrial  
32-Pb Plastic Leaded Chip Carrier - Tape and Reel  
32-Pb Plastic Leaded Chip Carrier  
32-Pb Plastic Leaded Chip Carrier - Tape and Reel  
32-Pb Plastic Leaded Chip Carrier  
[27]  
CY7B992–5JI  
CY7B992–5JIT  
CY7B992–7JC  
CY7B992–7JCT  
CY7B992–7JI  
32-Pb Plastic Leaded Chip Carrier - Tape and Reel  
32-Pb Plastic Leaded Chip Carrier  
Industrial  
750  
Commercial  
Commercial  
Industrial  
32-Pb Plastic Leaded Chip Carrier - Tape and Reel  
32-Pb Plastic Leaded Chip Carrier  
CY7B992–7LMB  
32-Pin Rectangular Leadless Chip Carrier  
Military  
Pb-Free  
250  
CY7B991–2JXC  
32-Pb Plastic Leaded Chip Carrier  
Commercial  
Commercial  
Commercial  
Commercial  
Industrial  
CY7B991–2JXCT  
CY7B991–5JXC  
CY7B991–5JXCT  
CY7B991–5JXI  
CY7B991–5JXIT  
CY7B991–7JXC  
CY7B991–7JXCT  
CY7B992–5JXI  
CY7B992–5JXIT  
32-Pb Plastic Leaded Chip Carrier - Tape and Reel  
32-Pb Plastic Leaded Chip Carrier  
500  
32-Pb Plastic Leaded Chip Carrier - Tape and Reel  
32-Pb Plastic Leaded Chip Carrier  
32-Pb Plastic Leaded Chip Carrier - Tape and Reel  
32-Pb Plastic Leaded Chip Carrier  
Industrial  
750  
500  
Commercial  
Commercial  
Industrial  
32-Pb Plastic Leaded Chip Carrier - Tape and Reel  
32-Pb Plastic Leaded Chip Carrier  
32-Pb Plastic Leaded Chip Carrier - Tape and Reel  
Industrial  
Note  
27. Not recommended for the new design.  
Document Number: 38-07138 Rev. *B  
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CY7B991  
CY7B992  
Military Specifications  
Group A Subgroup Testing  
DC Characteristics  
Parameter  
Subgroups  
V
1, 2, 3  
1, 2, 3  
1, 2, 3  
1, 2, 3  
1, 2, 3  
1, 2, 3  
1, 2, 3  
1, 2, 3  
1, 2, 3  
1, 2, 3  
1, 2, 3  
1, 2, 3  
1, 2, 3  
1, 2, 3  
OH  
V
OL  
V
IH  
V
IL  
V
IHH  
V
IMM  
V
ILL  
I
IH  
I
IL  
I
IHH  
I
IMM  
I
ILL  
I
CCQ  
I
CCN  
Package Diagrams  
Figure 9. 32-Pin Plastic Leaded Chip Carrier  
51-85002-*B  
Document Number: 38-07138 Rev. *B  
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CY7B991  
CY7B992  
Package Diagrams (continued)  
Figure 10. 32-Pin Rectangular Leadless Chip Carrier  
MIL-STD-1835 C-12  
51-85002-*B  
Document Number: 38-07138 Rev. *B  
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CY7B991  
CY7B992  
Document History  
Document Title: CY7B991/CY7B992 Programmable Skew Clock Buffer  
Document Number: 38-07138  
Orig. of  
Change  
REV.  
ECN NO. Issue Date  
Description of Change  
**  
110247  
12/19/01  
SZV  
Change from Specification number: 38-00513 to 38-07138  
*A  
1199925  
See ECN KVM/AESA Add Pb-free part numbers. Update package names in Ordering Information  
table. Remove Pentium reference on page 1.  
*B  
1286064  
See ECN  
AESA  
Change status to final  
© Cypress Semiconductor Corporation, 2001-2007. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the use of  
any circuitry other than circuitry embodied in a Cypress product. Nor does it convey or imply any license under patent or other rights. Cypress products are not warranted nor intended to be used for  
medical, life support, life saving, critical control or safety applications, unless pursuant to an express written agreement with Cypress. Furthermore, Cypress does not authorize its products for use as  
critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress products in life-support systems  
application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges.  
Any Source Code (software and/or firmware) is owned by Cypress Semiconductor Corporation (Cypress) and is protected by and subject to worldwide patent protection (United States and foreign),  
United States copyright laws and international treaty provisions. Cypress hereby grants to licensee a personal, non-exclusive, non-transferable license to copy, use, modify, create derivative works of,  
and compile the Cypress Source Code and derivative works for the sole purpose of creating custom software and or firmware in support of licensee product to be used only in conjunction with a Cypress  
integrated circuit as specified in the applicable agreement. Any reproduction, modification, translation, compilation, or representation of this Source Code except as specified above is prohibited without  
the express written permission of Cypress.  
Disclaimer: CYPRESS MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARD TO THIS MATERIAL, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES  
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Cypress reserves the right to make changes without further notice to the materials described herein. Cypress does not  
assume any liability arising out of the application or use of any product or circuit described herein. Cypress does not authorize its products for use as critical components in life-support systems where  
a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress’ product in a life-support systems application implies that the manufacturer  
assumes all risk of such use and in doing so indemnifies Cypress against all charges.  
Use may be limited by and subject to the applicable Cypress software license agreement.  
Document Number: 38-07138 Rev. *B  
Revised June 22, 2007  
Page 19 of 19  
PSoC Designer™, Programmable System-on-Chip™, and PSoC Express™ are trademarks and PSoC® is a registered trademark of Cypress Semiconductor Corp. All other trademarks or registered  
2
trademarks referenced herein are property of the respective corporations. Purchase of I C components from Cypress or one of its sublicensed Associated Companies conveys a license under the  
2
2
2
Philips I C Patent Rights to use these components in an I C system, provided that the system conforms to the I C Standard Specification as defined by Philips. All products and company names  
mentioned in this document may be the trademarks of their respective holders.  
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