Frequency Generator & Integrated Buffers - Integrated Circuit Systems
Description
Integrated Circuit Systems, Inc.
ICS9148-17
Frequency Generator & Integrated Buffers for PENTIUM/ProTM
General Description
The ICS9148-17 generates all clocks required for high speed RISC or CISC microprocessor systems such as Intel PentiumPro or Cyrix.
Eight different reference frequency multiplying factors are externally selectable with smooth frequency transitions.
Features include four CPU, six PCI, two AGP (=2xPCI) and Twelve SDRAM clocks.
Two reference outputs are available equal to the crystal frequency.
One 48 MHz for USB, and one 24 MHz clock for Super IO.
Built in ±1.
5%, 0.
6% center or down spread spectrum modulation to reduce EMI.
Serial programming I2C interface allows changing functions, stop clock programing and frequency selection.
Additionally, the device meets the Pentium power-up stabilization, which requires that CPU and PCI clocks be stable within 2ms after power-up.
High drive PCICLK and SDRAM outputs typically provide greater than 1 V/ns slew rate into 30pF loads.
CPUCLK outputs typically provide better than 1V/ns slew rate into 20pF loads while maintaining 50±5% duty cycle.
The REF and 24 and 48 MHz clock outputs typically provide better than 0.
5V/ns slew rates.
Features
3.
3V outputs: SDRAM, AGP, PCI, REF, 48/24 MHz 2.
5V or 3.
3V outputs: CPU 20 ohm CPU clock output impedance 20 ohm PCI clock output impedance CPU to PCI skew = 2 to 6ns No external load cap for CL=18pF crystals 250 ps max CPU, PCI clock skew Smooth CPU frequency transition among all CPU frequencies.
I2C interface for programming 2ms power up clock stable time Clock duty cycle 45-55%.
48 pin 300 mil SSOP package 3.
3V operation, 5V tolerant inputs.
Pin Configuration
Block Diagram
PLL2 /2 X1 X2 XTAL OSC
STOP
48MHz 24MHz REF (0:1) AGP(0:1)
2
PLL1 Spread Spectrum FS(0:2) MODE CPU3.
3#_2.
5
STOP
4
CPUCLK (0:3)
48-Pin SSOP
* Internal Pull-up Resistor of 240K to 3.
3V on indicated inputs
CPU_STOP
3
LATCH
PCI CLOCK DIVDER
12
SDRAM (0:11)
5
POR
ST...
Similar Datasheet
