ICS9148-75 Datasheet, PDF (1/17 Pages) Integrated Circuit Systems – Frequency Generator & Integrated Buffers for Mother Boards

Integrated
Circuit
Systems, Inc.
ICS9148 - 75
Preliminary Product Preview
Frequency Generator & Integrated Buffers for Mother Boards
General Description
The ICS9148-75 generates all clocks required for high speed
RISC or CISC microprocessor systems such as Intel
PentiumPro™, AMD™ or Cyrix™. Sixteen different reference
frequency multiplying factors are externally selectable with
smooth frequency transitions.
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 ICS9148-75
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
SDRAM12 output may be used as a feed back into an off chip
PLL.
Block Diagram
Features
• Generates the following system clocks:
- 3 CPU(2.5V/3.3V) up to 100MHz.
- 6 PCI(3.3V) @ 33.3MHz (including one free
running PCICLK)
- 3AGP(3.3V) @ 2 x PCI
- 13 SDRAMs(3.3V) up to 100MHz
- 1 REF (3.3V) @ 14.318MHz
- 1 - 48MHz (3.3V) fixed
• Skew characteristics:
- CPU – CPU<250ps
- CPU(early) – PCI : 1-4ns
- AGP – PCI: 250ps
- PCI – PCI <500ps
• Supports Spread Spectrum modulation & I²C
programming for Power Management, Frequency Select
• Efficient Power management scheme through power
down PCI, AGP and CPU_STOP clocks.
• Uses external 14.318MHz crystal
• 48 pin 300mil SSOP.
Pin Configuration
Power Groups
VDD1 = REF (0:1), X1, X2
VDD2 = PCICLK_F, PCICLK(0:5)
VDD3 = SDRAM (0:11), supply for PLL core
VDD4 = AGP (1:2)
VDD5 = Fixed PLL, 48MHz , AGP0
VDDL = CPUCLK (0:3)
9148-75 Rev C 3/01/00
48-Pin SSOP
* Internal Pull-up Resistor of
240K to 3.3V on indicated inputs
Pentium is a trademark of Intel Corporation
I²C is a trademark of Philips Corporation
PRODUCT PREVIEW documents contain information on new
products in the sampling or preproduction phase of development.
Characteristic data and other specifications are subject to change
without notice.