CY2308
3.3V Zero Delay Buffer
Cypress Semiconductor Corporation
•
198 Champion Court
•
San Jose
, CA 95134-1709
•
408-943-2600
Document Number: 38-07146 Rev. *F
Revised September 19, 2008
Features
■ Zero input-output propagation delay, adjustable by
capacitive load on FBK input
■ Multiple configurations, see “Available CY2308
Configurations” on page 3
■ Multiple low skew outputs
■ Two banks of four outputs, three-stateable by two select
inputs
■ 10 MHz to 133 MHz operating range
■ 75 ps typical cycle-to-cycle jitter (15 pF, 66 MHz)
■ Space saving 16-pin 150 mil SOIC package or 16-pin TSSOP
■ 3.3V operation
■ Industrial Temperature available
Functional Description
The CY2308 is a 3.3V Zero Delay Buffer designed to distribute
high speed clocks in PC, workstation, datacom, telecom, and
other high performance applications.
The part has an on-chip PLL that locks to an input clock
presented on the REF pin. The PLL feedback is driven into the
FBK pin and obtained from one of the outputs. The
input-to-output skew is less than 350 ps and output-to-output
skew is less than 200 ps.
The CY2308 has two banks of four outputs each that is
controlled by the Select inputs as shown in the table “Select
Input Decoding” on page 2”. If all output clocks are not
required, Bank B is three-stated. The input clock is directly
applied to the output for chip and system testing purposes by
the select inputs.
The CY2308 PLL enters a power down state when there are
no rising edges on the REF input. In this mode, all outputs are
three-stated and the PLL is turned off resulting in less than
50
μA of current draw. The PLL shuts down in two additional
cases as shown in the table “Select Input Decoding” on
page 2.
Multiple CY2308 devices accept the same input clock and
distribute it in a system. In this case, the skew between the
outputs of two devices is less than 700 ps.
The CY2308 is available in five different configurations as
shown in the table “Available CY2308 Configurations” on
page 3. The CY2308–1 is the base part where the output
frequencies equal the reference if there is no counter in the
feedback path. The CY2308–1H is the high drive version of the
–1 and rise and fall times on this device are much faster.
The CY2308–2 enables the user to obtain 2X and 1X
frequencies on each output bank. The exact configuration and
output frequencies depend on the output that drives the
feedback pin. The CY2308–3 enables the user to obtain 4X
and 2X frequencies on the outputs.
The CY2308–4 enables the user to obtain 2X clocks on all
outputs. Thus, the part is extremely versatile and is used in a
variety of applications.
The CY2308–5H is a high drive version with REF/2 on both
banks.
REF
CLKA1
CLKA2
CLKA3
CLKA4
FBK
PLL
MUX
Select Input
Decoding
S2
S1
CLKB1
CLKB2
CLKB3
CLKB4
/2
Extra Divider (–2, –3)
/2
Extra Divider (–3, –4)
Extra Divider (–5H)
/2
Logic Block Diagram
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