CDC2516
3.3-V PHASE-LOCK LOOP CLOCK DRIVER
SCAS579A – OCTOBER 1996 – REVISED JANUARY 1998
DGG PACKAGE
(TOP VIEW)
Phase-Lock Loop Clock Distribution for
Synchronous DRAM Applications
Distributes One Clock Input to Four Banks
of Four Outputs
V
1Y0
1Y1
GND
GND
1Y2
1Y3
V
V
CC
1
2
3
4
5
6
7
8
9
48
47
46
45
44
43
42
41
40
CC
4Y0
4Y1
GND
GND
4Y2
4Y3
Separate Output Enable for Each Output
Bank
External Feedback Pin (FBIN) Is Used to
Synchronize the Outputs to the Clock Input
On-Chip Series-Damping Resistors
No External RC Network Required
V
CC
CC
1G
4G
Operates at 3.3-V V
CC
GND 10
AV
39 GND
Packaged in Plastic 48-Pin Thin Shrink
Small-Outline Package
AV
11
12
38
37
CC
CC
CLK
FBIN
AGND 13
AGND 14
GND 15
2G 16
36 AGND
35 FBOUT
34 GND
33 3G
description
The CDC2516 is a high-performance, low-skew,
low-jitter, phase-lock loop (PLL) clock driver. It
uses a PLL to precisely align, in both frequency
and phase, the feedback output (FBOUT) to the
clock (CLK) input signal. It is specifically designed
for use with synchronous DRAMs. The CDC2516
operates at 3.3-V V
series-damping resistors that make it ideal for
driving point-to-point loads.
V
17
32
V
CC
CC
2Y0 18
2Y1 19
GND 20
GND 21
2Y2 22
2Y3 23
31 3Y0
30 3Y1
29 GND
28 GND
27 3Y2
26 3Y3
and provides integrated
CC
V
24
25
V
CC
CC
Four banks of four outputs provide 16 low-skew,
low-jitter copies of the input clock. Output signal
duty cycles are adjusted to 50 percent,
independent of the duty cycle at the input clock.
Each bank of outputs can be enabled or disabled
separately via the 1G, 2G, 3G, and 4G control
inputs. When the G inputs are high, the outputs
switchinphaseandfrequencywithCLK;whenthe
G inputs are low, the outputs are disabled to the
logic-low state.
Unlike many products containing PLLs, the CDC2516 does not require external RC networks. The loop filter
for the PLL is included on-chip, minimizing component count, board space, and cost.
Because it is based on PLL circuitry, the CDC2516 requires a stabilization time to achieve phase lock of the
feedback signal to the reference signal. This stabilization time is required following power up and application
of a fixed-frequency, fixed-phase signal at CLK, as well as following any changes to the PLL reference or
feedback signals. The PLL may be bypassed for test purposes by strapping AV
to ground.
CC
The CDC2516 is characterized for operation from 0°C to 70°C.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
Copyright 1998, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
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