ICS9248-81 Datasheet, PDF (1/18 Pages) Integrated Circuit Systems – Frequency Generator & Integrated Buffers

Integrated
Circuit
Systems, Inc.
ICS9248- 81
Frequency Generator & Integrated Buffers
General Description
The ICS9248-81 is the single chip clock solution for Desktop/
Notebook designs using the SIS style chipset. It provides all
necessary clock signals for such a system.
Spread spectrum may be enabled through I²C programming.
Spread spectrum typically reduces system EMI by 8dB to
10dB. This simplifies EMI qualification without resorting to
board design iterations or costly shielding. The ICS9248-81
employs a proprietary closed loop design, which tightly
controls the percentage of spreading over process and
temperature variations.
Serial programming I²C interface allows changing functions,
stop clock programming and frequency selection. The SD_SEL
latched input allows the SDRAM frequency to follow the
CPUCLK frequency(SD_SEL=1) or other clock frequencies
(SD_SEL=0)
Block Diagram
Features
• Generates the following system clocks:
- 3 CPU(2.5V/3.3V) up to 133.3MHz.
- 6 PCI(3.3V) (including 1 free-running)
- 13 SDRAMs(3.3V) up to 133.3MHz.
- 3 REF (3.3V) @ 14.318MHz
- 1 clock @ 24/14.3 MHz selectable output for SIO
- 1 Fixed clock at 48MHz (3.3V)
- 1 IOAPIC @ 2.5V / 3.3V
• Skew characteristics:
- CPU – CPU<175ps
- SDRAM – SDRAM < 250ps
- CPU–SDRAM < 500ps
- CPU(early) – PCI : 1-4ns (typ. 3ns)
- PCI – PCI <500ps
• Supports Spread Spectrum modulation ±0.25 & ±0.5%
center spread
• Serial I²C interface for Power Management, Frequency
Select, Spread Spectrum.
• Efficient Power management scheme through PCI,
SDRAM, CPU STOP CLOCKS and PD#.
• Uses external 14.318MHz crystal
• 48 pin 300mil SSOP.
Pin Configuration
Power Groups
VDDREF = REF [2:0], X1, X2
VDDPCI = PCICLK_F, PCICLK [4:0]
VDDSD/C = SDRAM [11:0], supply for PLL core, 24 MHz, 48MHz
VDD/CPU = CPUCLK [3:1]
VDDLAPIC = IOAPIC
GNDFIX = Ground for fixed clock PLL and output buffers
9248-81 Rev E 10/12/99
48-Pin SSOP
* Internal Pull-up Resistor of
120K to 3.3V on indicated inputs
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.