General Description

The ICS9148-47 is part of a reduced pin count two-chip clock solution for designs using an Intel BX style chipset. Companion SDRAM buffers are ICS9179-11 and -12.

There are two PLLs, with the first PLL capable of spread spectrum operation. Spread spectrum typically reduces system EMI by 8-10dB. The second PLL provides support for USB (48MHz) and 24MHz requirements. CPU frequencies up to 100MHz are supported.

The I2C interface allows stop clock programming, frequency selection, and spread spectrum operation to be programmed. Clock outputs include two CPU (2.5V or 3.3V), seven PCI (3.3V), one REF (3.3V), one IOAPIC (2.5V or 3.3V), one 48MHz, and one selectable 48/24MHz.

Features

• Generates system clocks for CPU, PCI, IOAPIC, 14.314 MHz, 48 and 24MHz.

• Supports single or dual processor systems

• Skew from CPU (earlier) to PCI clock 1 to 4ns

• Separate 2.5V and 3.3V supply pins

• 2.5V outputs: CPU, IOAPIC

• 3.3V outputs: PCI, REF

• No power supply sequence requirements

• 28 pin SOIC

• Spread Sectrum operation optional for PLL1

• CPU frequencies to 100MHz are supported.