Integrated
Circuit
Systems, Inc.
ICS90C65
Dual Voltage Video/Memory Clock Generator
Introduction
The Integrated Circuit Systems
ICS90C65
is a dual clock
generator for VGA applications. It simultaneously generates
two clocks. One clock is for the video memory, and the other
is the video dot clock.
The
ICS90C65
has been specifically designed to serve the
portable PC market with operation at either 3.3V or 5V with a
comprehensive power-saving shut-down mode.
This data sheet supplies sales order information, a functional
overview, signal pin details, a block diagram, AC/DC charac-
teristics, timing diagrams, and package mechanical information.
Features
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Specified for dual voltage operation (V
DD
=3.3V or 5V),
but operates continuously from 3.0V to 5.25V
Designed to be powered-down for extended battery life
Backward compatibility to the ICS90C64 and ICS90C63
Dual Clock generator for the IBM-compatible Western
Digital Imaging Video Graphics Array (VGA) LSI
devices, and 8514/A chip sets
Integral loop filter components, reduce cost and phase
jitter
Generates fifteen video clock frequencies (including
25.175 and 28.322 MHz) derived from a 14.318 MHz
system clock reference frequency
On-chip generation of eight memory clock frequencies
Video clock is selectable among the 15 internally gener-
ated clocks and one external clock
CMOS technology
Available in 20-pin PLCC, SOIC and DIP packages
Description
The Integrated Circuit Systems Video Graphics Array Clock
Generator (ICS90C65) is capable of producing different out-
put frequencies under firmware control. The video output
frequency is derived from a 14.318 MHz system clock avail-
able in IBM PC/XT/AT and Personal System/2 computers. It
is designed to work with Western Digital Imaging Video
Graphics Array and 8514/A devices to optimize video subsys-
tem performance.
The video dot clock output may be one of 15 internally-
generated frequencies or one external input. The selection of
the video dot clock frequency is done through four inputs.
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VSEL0
VSEL1
VSEL2
VSEL3
VSEL0 and VSEL1 are latched by the SELEN signal. VSEL2
and VSEL3 are used as direct inputs to the VCLK selection.
Table 1-1 is the truth table for VCLK selection.
The input and truth table have been designed to allow a direct
connection to one of the many Western Digital Imaging VGA
controllers or 8514/A chip sets.
The MCLK output is one of eight internally-generated frequen-
cies as shown in Table 1-2. The various VCLK and MCLK
frequencies are derived from the 14.318 MHz input frequency.
The VCLKE and MCLKE input can tristate the VCLK and
MCLK outputs to facilitate board level testing.
Note:ICS90C65N (DIP) pin-out is identical to ICS90C65M (SOIC) pin-out.
90C65ARevA111095
ICS [ INTEGRATED CIRCUIT SYSTEMS ]
