Document
Integrated Circuit Systems, Inc.
AV9155
Low Cost 20-Pin Frequency Generator
General Description
The AV9155 is a low cost frequency generator designed specifically for desktop and notebook PC applications. Its CPU clocks provide all necessary CPU frequencies for 286, 386 and 486 systems, including support for the latest speeds of processors. The device uses a 14.318 MHz crystal to generate the CPU and all peripheral clocks for integrated desktop motherboards. The dual 14.318 MHz clock outputs allows one output for the system and one to be the input to an ICS graphics frequency generator such as the AV9194. The CPU clock offers the unique feature of smooth, glitch-free transitions from one frequency to the next, making this ideal device to use whenever slowing the CPU speed. The AV9155 makes a gradual transition between frequencies, so that it obeys the Intel cycle-to-cycle timing specification for 486 systems. The simultaneous 2X and 1X CPU clocks offer controlled skew to within 1.5ns (max) of each other. ICS offers several versions of the AV9155. The different devices are shown below:
Features
Compatible with 286, 386, and 486 CPUs Supports turbo modes Generates communications clock, keyboard clock, floppy disk clock, system reference clock, bus clock and CPU clock Output enable tristates outputs Up to 100 MHz at 5V or 3.3V 20-pin DIP or SOIC All loop filter components internal Skew-controlled 2X and 1X CPU clocks Power-down option
ICS has been shipping motherboard frequency generators since April 1990, and is the leader in the area of multiple output clocks on a single chip. The AV9155 is a third generation device, and uses ICSs patented analog CMOS phase-locked loop technology for low phase jitter. ICS offers a broad family of frequency generators for motherboards, graphics and other applications, including cost-effective versions with only one or two output clocks. Consult ICS for all of your clock generation needs.
PART
DESCRIPTION
AV9155C-01 Motherboard clock generator with 16 MHz BUS CLK AV9155C-02 Motherboard clock generator with 32 MHz BUS CLK AV9155C-23 Includes Pentium™ frequencies AV9155C-36 Features a special 40 MHz SCSI clock
Block Diagram
Pentium is a trademark of Intel Corporation.
9155 Rev B 8/24/98
AV9155
Pin Configuration
20-Pin DIP or SOIC
20-Pin DIP or SOIC
Pin Descriptions for AV 9155-01, 9155-02
PIN N UM BER 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 X2 X1 VDD GN D 16 M Hz/32 M Hz 24 M Hz 12 M Hz AGN D OE FS2 PD# 14.318 M Hz 14.318 M Hz GN D VDD 2XC PU C PU FS1 FS0 PIN N AM E 1.843 M Hz TYPE O utput O utput Input O utput O utput O utput Input Input Input O utput O utput O utput O utput Input Input 1.84 M Hz clock output. C rystal connection. C rystal connection. Digital power supply (3.3V or 5.0V). Digital Ground. 16 M Hz (-01) or 32 M Hz (-02) clock output. 24 M Hz floppy disk/combination I/O clock output. 12 M Hz keyboard clock output. Analog ground (original version). O utput enable. Tristates all outputs when low. (Has internal pull-up.) C PU clock frequency select #2. (Has internal pull-up.) Power-down. Shuts off entire chip when low. (Has internal pull-up.) 14.318 M Hz reference clock output. 14.318 M Hz reference clock output. Digital ground. Digital power supply (3.3V or 5.0V). 2X C PU clock output. 1X C PU clock output. C PU clock frequency select #1. (Has internal pull-up.) C PU clock frequency select #0. (Has internal pull-up.) DESC RIPTIO N
2
AV9155
Functionality - AV9155-01
(Using 14.318 MHz input. All frequencies in MHz.) CLOCK#2 CPU and 2XCPU
FS2 (Pin 11) 0 0 0 0 1 1 1 1 FS1 (Pin 19) 0 0 1 1 0 0 1 1 FS0 (Pin 20) 0 1 0 1 0 1 0 1 2XCPU (Pin 17) 8 16 32 40 50 66.66 80* 100* CPU (Pin 18) 4 8 16 20 25 33.33 40* 50*
PERIPHERAL CLOCKS
COMMCLK (Pin 1) 1.843* BUSCLK (Pin 6) 16* FDCLK (Pin 7) 24* KBCLK (Pin 8) 12*
REFERENCE CLOCKS
REFCLK1 (Pin 13) 14.318 REFCLK2 (Pin 14) 14.318
*5V only.
Functionality - AV9155-02
CLOCK#2 CPU and 2XCPU
FS2 (Pin 11) 0 0 0 0 1 1 1 1 FS1 (Pin 19) 0 0 1 1 0 0 1 1 FS0 (Pin 20) 0 1 0 1 0 1 0 1
(Using 14.318 MHz input. All frequencies in MHz.) PERIPHERAL CLOCKS
2XCPU (Pin 17) 8 16 32 40 50 66.66 80* 100* CPU (Pin 18) 4 8 16 20 25 33.33 40* 50*
COMMCLK (Pin 1) 1.843* BUSCLK (Pin 6) 32* FDCLK (Pin 7) 24* KBCLK (Pin 8) 12*
REFERENCE CLOCKS
REFCLK1 (Pin 13) 14.318 REFCLK2 (Pin 14) 14.318
*5V only.
Frequency Transitions
A key feature of the AV9155 is its ability to provide smooth, glitch-free frequency transitions on the CPU and 2XCPU clocks when the frequency select pins are changed. These frequency transitions do not violate the Intel 486 specification of less than 0.1% frequency change per clock period.
Using an Input Clock as Reference
The AV9155 is designed to accept a 14.318 MHz crystal as the input reference. With some external changes, it is possible to use a crystal oscillator or clock input. Please see application note AN04 for details on driving the AV9155 with a clock.
3
AV9155
Pin Configuration.