PI6C991 View Datasheet(PDF) - Pericom Semiconductor
Part Name
Description
View to exact match
PI6C991 Datasheet PDF : 9 Pages
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5V High-Speed Programmable
Skew Clock Buffer - SuperClockTM
Product Features
• Four pairs of programmable skew outputs
• 3.75 to 80 MHz output operation
• User-selectable output functions:
− Selectable skews
− Inverted and noninverted
− Operation at ½ and ¼ input frequency
− Operation at 2X and 4X input frequency
• Low skew <100ps typical, same pair. 250ps max.
• Allow REF clock input to have Spread Spectrum
modulation for EMI reduction
• 2X, 4X, ½ and ¼ outputs
• 3-level inputs for skew and output frequency control
• External feedback, internal loop filter
• Low cycle-to-cycle Jitter: <25ps RMS
• Duty cycle of output clock signals: 45% min. 55% max.
• Compatible with Pentium based processor
• Same pinout as Cypress CY7B991
• Packaged in Plastic 32-pin PLCC Package
Description
The PI6C991 is a low-skew, low jitter, 5V phase-lock loop (PLL)
programmable skew clock driver, for high performance comput-
ing and networking applications. This part offers user selectable
skew-control of 4 output pairs, providing the timing delays neces-
sary to optimize high performance clock distribution circuits.
Each output can be hardwired to one of nine delay or function
configurations. Delay increments are determined by the input clock
frequency and the configurations selected by the user.
The PI6C991 allows the REF clock input to have Spread Spectrum
modulation for EMI reduction.
The PI6C991 is pin-compatible with Cypress RoboClock CY7B991,
with improved AC/DC characteristics.
Logic Block Diagram
TEST
FB Phase
REF
Freq
Det
Filter
FS
4F0
4F1
3F0
3F1
Three Level
Select Inputs
2F0
2F1
1F0
1F1
Vco and
Time Unit
Generator
SKEW
SELECT
MATRIX
Pin Configuration
4Q0
4Q1
3Q0
3Q1
2Q0
2Q1
1Q0
1Q1
3F1
4F0
4F1
VCCQ
VCCN
4Q1
4Q0
GND
GND
4 3 2 1 32 31 30
5
29
6
28
7
27
32-Pin
8
J
26
9
25
10
24
11
23
12
22
13
21
14 15 16 17 18 19 20
2F0
GND
1F1
1F0
VCCN
1Q0
1Q1
GND
GND
1
PS8448 10/10/00
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