.........................Document #: 38-07459 Rev. *F Page 2 of 6
Zero-delay Buffer
When used as a zero-delay buffer the CY2SSTV855 will likely
be in a nested clock tree application. For these applications
the CY2SSTV855 offers a differential clock input pair as a PLL
reference. The CY2SSTV855 then can lock onto the reference
and translate with near zero delay to low-skew outputs. For
normal operation, the external feedback differential input,
FBINT/C, is connected to the feedback output, FBOUTT/C. By
connecting the feedback output to the feedback input the
propagation delay through the device is eliminated. The PLL
works to align the output edge with the input reference edge
thus producing a near zero delay. The reference frequency
affects the static phase offset of the PLL and thus the relative
delay between the inputs and outputs.
When AVDD is strapped LOW, the PLL is turned off and
bypassed for test purposes.
Pin Definition
[1, 2]
Pin Name I/O Description
6CLKINTITrue Clock Input. Low Voltage Differential True Clock Input.
7CLKINCIComplementary Clock Input. Low Voltage Differential Complementary Clock Input.
22 FBINC I Feedback Complementary Clock Input. Differential Input Connect to FBOUTC for
accessing the PLL.
23 FBINT I Feedback True Clock Input. Differential Input Connect to FBOUTT for accessing the
PLL.
3,12,17,26 YT(0:3) O True Clock Outputs. Differential Outputs.
2,13,16,27 YC(0:3) O Complementary Clock Outputs. Differential Outputs.
19 FBOUTT O Feedback True Clock Output. Differential Outputs. Connect to FBINT for normal
operation. A bypass delay capacitor at this output will control Input Reference/Output
Clocks phase relationships.
20 FBOUTC O Feedback Complementary Clock Output. Differential Outputs. Connect to FBINC for
normal operation. A bypass delay capacitor at this output will control Input
Reference/Output Clocks phase relationships.
24 PWRDWN I Control input to turn device in the power-down mode.
4,8,11,18,21,25 VDDQ 2.5V Power Supply for Output Clock Buffers.2.5V Nominal.
9AVDD2.5V Power Supply for PLL. 2.5V Nominal.
1,5,14,15,28 GND Ground
10 AGND Analog Ground. 2.5V Analog Ground.
Function Table
Inputs Outputs
PLLAVDD PWRDWN CLKINT CLKINC YT(0:3) YC(0:3) FBOUTT FBOUTC
GND H L
H
L H L H BYPASSED/OFF
GND H H L H L H L BYPASSED/OFF
2.5V H L H L H L H On
2.5V H H L H L H L On
2.5V X < 20 MHz < 20 MHz Hi-Z Hi-Z Hi-Z Hi-Z Off
Notes:
1. PU = internal pull-up.
2. A bypass capacitor (0.1F) should be placed as close as possible to each positive power pin (< 0.2”). If these bypass capacitors are not close to the pins their
high frequency filtering characteristic will be cancelled by the lead inductance of the traces.
