General Description

The ICS9250-13 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 ICS9250-13 employs a proprietary closed loop design, which tightly controls the percentage of spreading over process and temperature variations.

Features

• 3.3V outputs: SDRAM, PCI, REF, 48/24MHz

• 2.5V or 3.3V outputs: CPU

• 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 CL=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%.

• 56 pin 300 mil SSOP package

• 3.3V operation, 5V tolerant input.

Recomended Application:

• 440LX/EX type chipset Motherboard single chip clock solution