ICST AV9131-01CN16, ICS9131-01CN16, ICS9131-01CS16 Datasheet

Integrated
Circuit
Systems, Inc.

General Description Features

ICS9131

Block Diagram

32 KhZ Motherboard Frequency Generator

9131 Rev B 052897P

The ICS9131 offers a tiny footprint solution for generating
a selectable CPU clock from a 32.768 kHz crystal. The device
allows a variety of microprocessors to be clocked by changing
the state of address lines FS0, FS1, and FS2. The ICS9131 is
the ideal solution for replacing high speed oscillators and for
reducing clock speeds to save power in computers. The
device provides smooth, glitch-free frequency transitions so
that the CPU can continue to operate during slow down or
speed up. The rate of frequency change makes the ICS9131
compatible with all 386DX, 386SX, 486DX, 486DXZ, 486SX
and Pentium™ microprocessors.

The ICS9131 is driven from a single 32.768 kHz crystal. The
only external components required are the crystal and a 10M
ohm resistor. The device generates the 14.318 MHz system
clock, eliminating the need for a 14.318 MHz crystal. High­Performance applications may require high speed clock
termination components.

• Single 32.768 kHz crystal generates system clock and
selectable CPU clock

• Generates CPU clocks from 8 MHz to 100 MHz.

• Operates from 3.3V or 5.0V supply

• Operates up to 66 MHz at 3.3V

• Separate VDD for 32 kHz clock enables it to run from
battery

• STOPCLK feature allows for a glitch-free turn-on and
Pen-turn-off of the CPU clock to static processors

• Output enable tristates outputs

• 16-pin PDIP or SOIC package

• Frequency selects allow for a smooth transition of
the CPUCLK

VDD32 Supply

The ICS9131 has a separate power supply for the 32.768 kHz
oscillator circuitry. This allows the 32 kHz clock to run from
a battery or other source while the main power to the chip is
disconnected. The VDD32 supply is guaranteed to operate
down to +2.0V, with the clock consuming less than 10µA at
+3.3V and the main VDD at 0V.

The frequencies and power-down options in the ICS9131 are
mask programmable. Customer specific masks can be made
and prototypes delivered within 6-8 weeks from receipt of
order. ICS also offers standard versions, such as those de­scribed in this data sheet.

Pentium is a trademark of Intel.

Pin Configuration

16-Pin DIP or SOIC

2

ICS9131

Pin Descriptions

Functionality

FS2 FS1 FS0 CPUCLK ACTUALS

0
0
0
0
1
1
1
1

0
0
1
1
0
0
1
1

0
1
0
1
0
1
0
1

16
25

33.3
40
50
60

66.6
80

16.004

25.059

33.412

40.095

50.119

60.142

66.484

80.190

PIN NUMBER PIN NAME TYPE DESCRIPTION

1 32 kHz Output 32.768 kHz output.
2 X2 Output

Connect 32 kHz crystal, this input includes internal load
capacitor for crystal.

3 X1 Input

Connect 32 kHz crystal, this input includes internal load

capacitor for crystal.
4 VDD32 -- Power Supply for 32 kHz oscillator.
5 VCC -- Power Supply.
6 VSS -- Ground.
7 AGND -- Analog Ground.
8 OE Input OE tristates outputs when low.
9 FS2 Input CPU clock frequency select 2.

10 REFCLK Output 14.318 M Hz output.
11 STOPCLK# Input Stops CPU clock when low.
12 VSS -- Ground.
13 VCC -- Power supply.
14 CPUCLK Output CPU clock output (see Decoding table).
15 FS1 Input CPU clock frequency select 1.
16 FS0 Input CPU clock frequency select 0.

3

ICS9131

Recommended External Circuit

Notes:

1) The external components shown should be placed as close to the device as possible.

2) Pins 5 and 13 should be connected together externally. One decoupling capacitor may suffice for both pins.