
CDC913
PC MOTHERBOARD CLOCK GENERATOR
WITH DUAL 1-TO-4 BUFFERS AND 3-STATE OUTPUTS
SCAS502C – APRIL 1995 – REVISED MAY 1996
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POST OFFICE BOX 655303
DALLAS, TEXAS 75265
Generates Programmable CPU Clock
Output (50 MHz, 60 MHz, or 66 MHz)
Generates 33-MHz Clock for Asynchronous
PCI
One 14.318-MHz Reference Clock Output
All Output Clock Frequencies Derived From
a Single 14.31818-MHz Crystal Input
LVTTL-Compatible Inputs and Outputs
Internal Loop Filters for Phase-Lock Loops
Eliminate the Need for External
Components
Operates at 3.3-V V
CC
Package Options Include Plastic
Small-Outline (DW) and Shrink
Small-Outline (DB) Packages
description
The CDC913 is a high-performance clock generator with integrated dual 1-to-4 buffers, which simplifies clock
system design for PC motherboards. The CDC913 consists of a crystal oscillator, two phase-locked loops (PLL),
and two 1-to-4 buffers. The CDC913 generates all frequencies using a single 14.318-MHz crystal.
The CPUCLK output is programmable to one of three frequencies (50 MHz, 60 MHz, or 66 MHz) via the SEL0
and SEL1 inputs. PCICLK outputs a 33-MHz clock, independent of the CPUCLK frequency. REFCLK provides
a buffered copy of the 14.318-MHz reference. The oscillator and PLLs in the CDC913 are bypassed when in
the TEST mode, i.e., SEL1 = SEL0 = H. When in the TEST mode, a test clock can be driven over the X1 input
and buffered out from the PCICLK, CPUCLK, and REFCLK outputs.
Outputs 1Yn and 2Yn are 3-state outputs and are enabled via OE. When OE is high, the outputs are in the
high-impedance state. When OE is low, the outputs are enabled.
Since the CDC913 is based on PLL circuitry, it requires a stabilization time to achieve phase lock of the PLL.
This stabilization time is required following power up and application of a fixed-frequency, fixed-phase signal
at the X1 input, and following any changes to the SELn inputs.
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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X1
X2
AGND
V
CC
1Y1
1Y2
1Y3
1Y4
GND
1A
CPUCLK
SEL0
A
VCC
REFCLK
OE
VCC
2Y1
2Y2
2Y3
2Y4
GND
2A
PCICLK
SEL1
DB OR DW PACKAGE
(TOP VIEW)
Copyright
1996, Texas Instruments Incorporated
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.