ICS9248-195 Datasheet, PDF (3/16 Pages) Integrated Circuit Systems – Frequency Generator & Integrated Buffers for PENTIUM II/III & K6

ICS9248 - 195
General Description
The ICS9248-195 is the single chip clock solution for Notebook designs using the 440BX, MX, VIA PM/PL/PLE 133
style chip set, with Coppermine or Tualatin processor, for Note book applications. 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-
195 employs a proprietary closed loop design, which tightly controls the percentage of spreading over process and
temperature variations.
Serial Configuration Command Bitmap
Byte0: Functionality and Frequency Select Register (default = 0)
Bit
Description
Bit 7 ^{0 = Center Spread Spectrum Modulation}
1 = Down Spread Spectrum Modulation
FS3 FS2 FS1 FS0
Center
Down
Bit2 Bit6 Bit5 Bit4 ^{CPUCLK PCICLK} Spread % Spread%
Bit 2,
6:4
Bit 3
Bit 1
Bit 0
0 0 0 0 66.67 33.33 ±0.35% -0.70%
0 0 0 1 100.00 33.33 ±0.35% -0.70%
0 0 1 0 66.67 33.33 ±0.60% -1.20%
0 0 1 1 133.33 33.33 ±0.35% -0.70%
0 1 0 0 66.67 33.33 ±0.23% -0.45%
0 1 0 1 100.00 33.33 ±0.23% -0.45%
0 1 1 0 100.00 33.33 ±0.60% -1.20%
0 1 1 1 133.33 33.33 ±0.23% -0.45%
1 0 0 0 66.67 33.33 ±0.45% -0.90%
1 0 0 1 100.00 33.33 ±0.45% -0.90%
1 0 1 0 90.00 30.00 ±0.35% -0.70%
1 0 1 1 133.33 33.33 ±0.45% -0.90%
1 1 0 0 70.00 35.00 ±0.35% -0.70%
1 1 0 1 105.00 35.00 ±0.35% -0.70%
1 1 1 0 133.33 33.33 ±0.60% -1.20%
1 1 1 1 140.00 35.00 ±0.35% -0.70%
0 - Frequency is selected by hardware select pins. Latched inputs.
1 - Frequency is controlled by I²C programming.
0 - Normal
1 - Spread Spectrum Enabled
0 - Running
1 - Tristate all outputs
PWD
1
Note1
0011
0
1
0
Notes:
1, Default at Power-up will be for latched logic inputs to define frequency. Bit [2, 6:4] are default to 0011.
2, PWD = Power-Up Default
0375D—02/02/04
3