ICS9248-131 Datasheet, PDF (3/16 Pages) Integrated Circuit Systems – Frequency Generator & Integrated Buffers for Celeron & PII/III™

ICS9248 - 131
General Description
The ICS9248-131 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.
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 ICS9248-131 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.
Mode Pin - Power Management Input Control
MODE, Pin 25
(Latched Input)
0
1
Pin 17
CPU_STOP#
(INPUT)
SDRAM 11
(OUTPUT)
Pin 18
PCI_STOP#
(INPUT)
SDRAM 10
(OUTPUT)
Pin 20
AGP_STOP#
(INPUT)
SDRAM 9
(OUTPUT)
Pin 21
PD#
(INPUT)
SDRAM 8
(OUTPUT)
Power Management Functionality
AGP_STOP# CPU_STOP# PCI_STOP#
1
0
1
AGP,
CPUCLK
Outputs
Stopped Low
PCICLK
(4:0)
Running
PCICLK_F,
REF, 48MHz
and SDRAM
Running
1
1
1
Running
Running
Running
1
1
0
Running Stopped Low Running
0
1
1
Running
Running
Running
Crystal
OSC
Running
Running
Running
Running
VCO
AGP
(1:0)
Running Running
Running Running
Running Running
Running Stopped Low
CPU 3.3#_2.5V Buffer selector for CPUCLK drivers.
CPU3.3#_2.5
Input level
(Latched Data)
1
0
Buffer Selected for
operation at:
2.5V VDD
3.3V VDD
3