CY7B991V
3.3V RoboClock
®
Low Voltage Programmable Skew Clock Buffer
Features
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Functional Description
The CY7B991V Low voltage Programmable Skew Clock Buffer
(LVPSCB) offers 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-performance 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. This delivers minimal and specified output skews and
full swing logic levels (LVTTL).
Each output is hardwired to one of nine delay or function config-
urations. Delay increments of 0.7 to 1.5 ns are determined by the
operating frequency with outputs able to skew up to ±6 time units
from their nominal “zero” skew position. The completely
integrated PLL allows external load and transmission line delay
effects to be canceled. When this “zero delay” capability of the
LVPSCB is combined with the selectable output skew functions,
the user can create output-to-output delays of up to ±12 time
units.
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 is multiplied by
two or four at the clock destination. This facility minimizes clock
distribution difficulty allowing maximum system clock speed and
flexibility.
All output pair skew <100 ps typical (250 max)
3.75 to 80 MHz output operation
User selectable output functions
❐
Selectable skew to 18 ns
❐
Inverted and non-inverted
1
1
❐
Operation at
⁄
2
and
⁄
4
input frequency
❐
Operation at 2x and 4x input frequency (input as low as 3.75
MHz)
Zero input to output delay
50% duty cycle outputs
LVTTL outputs drive 50Ω terminated lines
Operates from a single 3.3V supply
Low operating current
32-pin PLCC package
Jitter 100 ps (typical)
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Logic Block Diagram
TEST
FB
REF
FS
4F0
4F1
PHASE
FREQ
DET
FILTER
VCO AND
TIME UNIT
GENERATOR
4Q0
SELECT
INPUTS
(THREE
LEVEL)
4Q1
SKEW
3Q0
3Q1
SELECT
2Q0
MATRIX
2Q1
1Q0
1Q1
3F0
3F1
2F0
2F1
1F0
1F1
Cypress Semiconductor Corporation
Document Number: 38-07141 Rev. *C
•
198 Champion Court
•
San Jose
,
CA 95134-1709
•
408-943-2600
Revised June 20, 2007
CYPRESS [ CYPRESS SEMICONDUCTOR ]
