CDC2536_14 Datasheet, PDF (1/15 Pages) Texas Instruments – 3.3V PHASE-LOCK LOOP CLOCK DRIVER

CDC2536
www.ti.com
SCAS377E – APRIL 1994 – REVISED JULY 2004
3.3-V PHASE-LOCK LOOP CLOCK DRIVER WITH 3-STATE OUTPUTS
FEATURES
• Low Output Skew for Clock-Distribution and
Clock-Generation Applications
• Operates at 3.3-V V_CC
• Distributes One Clock Input to Six Outputs
• One Select Input Configures Three Outputs to
Operate at One-Half or Double the Input
Frequency
• No External RC Network Required
• On-Chip Series Damping Resistors
• External Feedback Pin (FBIN) Is Used to
Synchronize the Outputs to the Clock Input
• Application for Synchronous DRAM,
High-Speed Microprocessor
• TTL-Compatible Inputs and Outputs
• Outputs Drive 50-Ω Parallel-Terminated
Transmission Lines
• State-of-the-Art EPIC-IIB™ BiCMOS Design
Significantly Reduces Power Dissipation
• Distributed V_CC and Ground Pins Reduce
Switching Noise
• Packaged in Plastic 28-Pin Shrink
Small-Outline Package
DB PACKAGE
(TOP VIEW)
AV_{CC 1}
AGND ₂
CLKIN 3
SEL ₄
OE ₅
GND ₆
1Y1 ₇
V_CC 8
GND 9
1Y2 10
V_{CC 11}
GND ₁₂
1Y3 ₁₃
V_CC 14
28 ^AVCC
27 ^AGND
26 FBIN
25 ^TEST
24 ^CLR
23 ^VCC
22 ^2Y1
21 GND
20 VCC
19 2Y2
18 ^GND
17 ^VCC
16 ^2Y3
15 GND
DESCRIPTION
The CDC2536 is a high-performance, low-skew, low-jitter clock driver. It uses a phase-lock loop (PLL) to
precisely align, in both frequency and phase, the clock output signals to the clock input (CLKIN) signal. It is
specifically designed for use with synchronous DRAMs and popular microprocessors operating at speeds from
50 MHz to 100 MHz or down to 25 MHz on outputs configured as half-frequency outputs. The CDC2536
operates at 3.3-V V_CC and is designed to drive a 50-W transmission line. The CDC2536 also provides on-chip
series-damping resistors, eliminating the need for external termination components.
The feedback (FBIN) input is used to synchronize the output clocks in frequency and phase to the input clock
(CLKIN). One of the six output clocks must be fed back to FBIN for the PLL to maintain synchronization between
CLKIN and the outputs. The output used as the feedback pin is synchronized to the same frequency as CLKIN.
The Y outputs can be configured to switch in phase and at the same frequency as CLKIN. The select (SEL) input
configures three Y outputs to operate at one-half or double the CLKIN frequency, depending on which pin is fed
back to FBIN (see Tables 1 and 2). All output signal duty cycles are adjusted to 50% independent of the duty
cycle at the input clock.
Output-enable (OE) is provided for output control. When OE is high, the outputs are in the high-impedance state.
When OE is low, the outputs are active. TEST is used for factory testing of the device and can be use to bypass
the PLL. TEST should be strapped to GND for normal operation.
Unlike many products containing PLLs, the CDC2536 does not require external RC networks. The loop filter for
the PLL is included on-chip, minimizing component count, board space, and cost.
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.
EPIC-IIB is a trademark of Texas Instruments.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 1994–2004, Texas Instruments Incorporated