ICS9248DF-39T

ICS9248-39 Frequency Generator & Integrated Buffers for PENTIUM/ProTM General Description The ICS9248-39 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 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 ±0.5% or ±0.25% modulation to reduce the EMI. Serial programming I2C interface 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. 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 150 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)