ICS2495 Datasheet, PDF (1/7 Pages) Integrated Circuit Systems – Dual Video/Memory Clock Generator

Integrated
Circuit
Systems, Inc.
ICS2495
Dual Video/Memory Clock Generator
Features
• Low cost - eliminates need for multiple crystal clock • Buffered Xtal Out
oscillators in video display subsystems
• Integral Loop Filter components
• Mask-programmable frequencies
• Fast acquisition of selected frequencies, strobed or non-
• Pre-programmed versions for Industry Standard VGA
strobed
chips
• Guaranteed performance up to 135 MHz
• Glitch-free frequency transitions
• Excellent power supply rejection
• Internal clock remains locked when the external frequency
input is selected
• Low power CMOS device technology
• Advanced PLL for low phase-jitter
• Frequency change detection circuitry enhances new fre-
quency acquisition and eliminates problems caused by
• Small footprint - 16-pin DIP or SOIC
programs that rewrite frequency information
Description
Pin Configuration
The ICS2495 Clock Generator is an integrated circuit dual
phase-locked loop frequency synthesizer capable of generating
16 video frequencies and 4 memory clock frequencies for use
with high performance video display systems. Utilizing CMOS
technology to implement all linear, digital and memory func-
tions, the ICS2495 provides a low-power, small-footprint,
low-cost solution to the generation of video dot clocks. Outputs
are compatible with XGA, VGA, EGA, MCGA, CGA, MDA,
as well as the higher frequencies needed for advanced applica-
tions in desktop publishing and workstation graphics. Provi-
sion is made via a single level custom mask to implement
customer specific frequency sets. Phase-locked loop circuitry
permits rapid glitch-free transitions between clock frequencies.
In addition to providing 16 clock rates, the ICS2495 has
provisions to multiplex an externally-generated signal source
into the VCLK signal path. Internal phase-locked frequencies
continue to remain locked at their preset values when this mode
is selected. This feature permits instantaneous transition from
an external frequency to an internally-generated frequency.
Printed circuit board testing is simplified by the use of these modes
as an external clock generated by the ATE tester can be fed
through, permitting synchronous testing of the entire system.
XTAL2
1
EXTFREQ
2
FS0
3
FS1
4
STROBE
5
FS2
6
FS3
7
MS0
8
16
XTAL1
15
VCLK
14
XTALOUT
13
VSS
12
VDD
11
N/C
10
MCLK
9
MS1
16-Pin DIP or SOIC
Notes:
1. ICS2495M(SOIC) pinout is identical to ICS2495N(DIP).
ICS2595RevA090694