Clock Buffer. CY7C9915 Datasheet
3.3V Programmable Skew Clock Buffer
• All output pair skew <100 ps (typical)
• Input Frequency Range: 3.75 MHz to 150 MHz
• Output Frequency Range: 3.75 MHz to 150 MHz
• User-selectable output functions
— Selectable skew to 18 ns
— Inverted and non-inverted
— Operation at 1⁄2 and 1⁄4 input frequency
— Operation at 2x and 4x input frequency (input as low
as 3.75 MHz)
• 3.3V power supply
• ± 3.0% Output Duty Cycle Distortion
• LVTTL outputs drive 50Ω terminated lines
• Low operating current
• 32-pin PLCC package
• Jitter < 100ps peak-to-peak (< 15 ps RMS)
The CY7C9915 RoboClock is a 150-MHz Low-voltage
Programmable Skew Clock Buffer that offers user-selectable
control over system clock functions. This multiple-output clock
driver provides the system integrator with functions necessary
to optimize the timing of high-performance computer systems.
Eight individual drivers, arranged as four pairs of user-control-
lable outputs, can each drive terminated transmission lines
with impedances as low as 50Ω while delivering minimal and
specified output skews and full-swing logic levels (LVTTL).
Each output can be hardwired to one of nine delay or function
configurations. Delay increments of 0.42 to 1.6 ns are deter-
mined 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 trans-
mission 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
allow distribution of a low-frequency clock that can be multi-
plied by two or four at the clock destination. This facility
minimizes clock distribution difficulty while allowing maximum
system clock speed and flexibility.
4 3 2 1 32 31 30
14 15 16 17 18 19 20
Cypress Semiconductor Corporation • 3901 North First Street • San Jose, CA 95134 • 408-943-2600
Document #: 38-07687 Rev. *A
Revised April 29, 2005
Pin Definitions (CY7C9915)
26,27 1F0, 1F1
29,30 2F0, 2F1
4,5 3F0, 3F1
6,7 4F0, 4F1
23,24 1Q0, 1Q1
19,20 2Q0, 2Q1
14,15 3Q0, 3Q1
Reference Clock Input
Feedback Clock Input
Three Level Frequency Range Select
Three level function select for 1Q0,1Q1
Three level function select for 2Q0,2Q1
Three level function select for 3Q0,3Q1
Three level function select for 4Q0,4Q1
Three level select for test modes
3.3V Power Supply for output pair 1Q0 and 1Q1.
3.3V Power Supply for output pair 2Q0 and 2Q1.
3.3V Power Supply for output pair 3Q0 and 3Q1.
3.3V Power Supply for output pair 4Q0 and 4Q1.
3.3V Core Power
Block Diagram Description
Phase Frequency Detector and Filter
These two 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.
Table 1. Frequency Range Select and tU Calculation
FS Min. Max.
tU = f---N---O----M-1-----×----N---
where N =
At WhicnhstU = 1.0
LOW 15 30
MID 25 50
VCO and Time Unit Generator
HIGH 40 150
The VCO accepts analog control inputs from the PLL filter
block and generates a frequency that is 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 deter-
mined by the FS control pin. The time unit (tU) is determined
by the operating frequency of the device and the level of the
FS pin as shown in Table 1.
Skew Select Matrix
The skew select matrix is comprised of 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 below 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 connected to the FB input has
For all three-state inputs, HIGH indicates a connection
circuitry holds an unconnected input to VCC/2.
to VCC, LOW
connection. Internal termination
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Document #: 38-07687 Rev. *A
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