ICS9248-90

Features:

• 3.3V outputs: SDRAM, PCI, REF, 48/24MHz
• 2.5V outputs: CPU, IOAPIC
• 20 ohm CPU clock output impedance
• 20 ohm PCI clock output impedance
• Skew from CPU (earlier) to PCI clock - 1.5 to 4 ns, center 2.6 ns.
• No external load cap for CL=18pF crystals
• ±175 ps CPU clock skew
• 250ps (cycle to cycle) CPU jitter
• Smooth frequency switch, with selections from 66.8 to 133 MHz CPU.
• I2C interface for programming
• 3ms power up clock stable time
• Clock duty cycle 45-55%.
• 48 pin 300 mil SSOP package
• 3.3V operation, 5V tolerant inputs (with series R)
• <5ns propagation delay SDRAM from Buffer Input


Pinout




Specifications

Supply Voltage . . . . . . . . . . . . . . . . . . . .. . . . . . . .  . . . . . . 7.0 V
Logic Inputs . . . . . . . . . . . . . . .  . . . . GND 0.5 V to VDD +0.5 V
Ambient Operating Temperature . . . . . . . .. . .  . . . . 0 to +70
Case Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
Storage Temperature . . . . . . . . . . . . . . . . . . . . 65 to +150


Description

The ICS9248-90 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.
Features include two CPU, six PCI and thirteen SDRAM clocks. Two reference outputs of the ICS9248-90 are available equal to the crystal frequency. Plus the IOAPIC output powered by VDDL1. One 48 MHz for USB, and one 24 MHz clock for Super IO. Spread Spectrum built in at ±0.25% modulation to reduce the EMI.

Serial programming I2C interface of the ICS9248-90 allows changing functions, stop clock programing and Frequency selection. Additionally, the device meets the Pentium power-up stabilization, which requires that CPU and PCI clocks be stable within 2ms after power-up. It is not recommended to use I/O dual function pin for the slots (ISA, PIC, CPU, DIMM). The add on card might have a pull up or pull down.

High drive PCICLK and SDRAM outputs of the ICS9248-90 typically provide greater than 1 V/ns slew rate into 30pF loads. CPUCLK outputs typically provide better than 1V/ns slew rate into 20pF loads while maintaining 50 ±5% duty cycle. The REF and 24 and 48 MHz clock outputs typically provide better than 0.5V/ns slew rates into 20pF.