CY7B991V
3.3V RoboClock®
Low Voltage Programmable Skew Clock Buffer
Features
Functional Description
■
All Output Pair Skew <100 ps Typical (250 max)
■
3.75 MHz 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)
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).
■
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)
Each output is hardwired to one of nine delay or function configurations. 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.
Logic Block Diagram
TEST
PHASE
FREQ
DET
FB
REF
FILTER
VCO AND
TIME UNIT
GENERATOR
FS
4F0
4F1
3F0
3F1
4Q0
SELECT
INPUTS
(THREE
LEVEL)
4Q1
SKEW
3Q0
3Q1
SELECT
2F0
2F1
2Q0
MATRIX
2Q1
1Q0
1F0
1F1
1Q1
Cypress Semiconductor Corporation
Document Number: 38-07141 Rev. *E
•
198 Champion Court
•
San Jose, CA 95134-1709
•
408-943-2600
Revised September 10, 2009
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