ICS9148B-04 Datasheet, PDF (1/14 Pages) Integrated Circuit Systems – Frequency Generator & Integrated Buffers for PENTIUM/ProTM

Integrated
Circuit
Systems, Inc.
ICS9148 B -04
Frequency Generator & Integrated Buffers for PENTIUM/Pro^TM
General Description
The ICS9148B-04 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, seven PCI and Twelve SDRAM
clocks. Two reference outputs are available equal to the
crystal frequency. Plus the IOAPIC output powered byVDDL1.
One 48 MHz for USB, and one 24 MHz clock for Super IO.
Spread Spectrum built in - ±1.5% modulation to reduce the
EMI. Serial programming I²C interface allows changing
functions, stop clock programing and Frequency selection.
Rise time adjustment for VDD at 3.3V or 2.5V CPU.
Additionally, the device meets the Pentium power-up
stabilization, which requires that CPU and PCI clocks be
stable within 2ms after power-up. It is not recommended to
use I/O dual function pin for the slots (ISA, PCI, CPU, DIMM).
The add on card might have a pull up or pull down.
Features
• 3.3V outputs: SDRAM, PCI, REF, 48/24MHz
• 2.5V or 3.3V outputs: CPU, IOAPIC
• 20 ohm CPU clock output impedance
• 20 ohm PCI clock output impedance
• Skew from CPU (earlier) to PCI clock - 1 to 4 ns, center
2.6 ns.
• No external load cap for C_L=18pF crystals
• ±250 ps CPU, PCI clock skew
• 400ps (cycle to cycle) CPU jitter
• Smooth frequency switch, with selections from 50 to 83.3
MHz CPU.
• 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 input.
Pin Configuration
Block Diagram
9148-04 Rev B 01/20/98
48-Pin SSOP
* Internal Pull-up Resistor of
240K to 3.3V on indicated inputs
Power Groups
VDD1 = REF (0:1), X1, X2
VDD2 = PCICLK_F, PCICLK(0:5)
VDD3 = SDRAM (0:11), supply for PLL core,
24MHz, 48MHz
VDDL1 = IOAPIC
VDDL2 = CPUCLK (0:3)
Pentium is a trademark of Intel Corporation
I²C is a trademark of Philips Corporation
ICS reserves the right to make changes in the device data identified in this
publication without further notice. ICS advises its customers to obtain the latest
version of all device data to verify that any information being relied upon by the
customer is current and accurate.