ICS8431-21 is a clock frequency synthesizer from ICS, suitable for IA64/32 applications, with a frequency range of 250MHz to 700MHz and an output frequency range of 62.5MHz to 350MHz. The output frequency can be programmed using the parallel interface M0 to M8 to the configuration logic and the output divider control pin DIV_SEL. Spread spectrum clocking is programmed via the control inputs SSC_CTL0 and SSC_CTL1. The ICS8431-21's programmable features support four operational modes: spread spectrum clock (SSC), non-spread spectrum clock, and two test modes controlled by the SSC_CTL[1:0] pins. Unlike other synthesizers, the ICS8431-21 can immediately change spread-spectrum operation without having to reset the device. In SSC mode, the output clock is modulated in order to achieve a reduction in EMI. In one of the PLL bypass test modes, the PLL is disconnected as the source to the differential output allowing an external source to be connected to the TEST_I/O pin. This is useful for in-circuit testing and allows the differential output to be driven at a lower frequency throughout the system clock tree.
The ICS8431-21 is a high-performance clock frequency synthesizer from ICS, designed for applications requiring precise timing. It features a fully integrated PLL, differential 3.3V LVPECL output, and supports spread spectrum clocking to reduce EMI. The device operates with a crystal input range of 14–25 MHz and can output frequencies from 62.5 MHz to 350 MHz. It includes programmable modes for testing and characterization, with cycle-to-cycle jitter as low as 30 ps.
The synthesizer is configured via a parallel interface (M0–M8) and control pins (SSC_CTL0, SSC_CTL1, DIV_SEL). It supports four operational modes including spread spectrum, non-spread spectrum, and two PLL bypass modes for in-circuit testing. The device is available in a 28-lead SOIC package and operates from 0°C to 85°C.
| Output Frequency Range | 62.5 MHz to 350 MHz |
|---|---|
| Crystal Input Frequency Range | 14 MHz to 25 MHz |
| VCO Range | 250 MHz to 700 MHz |
| Cycle-to-Cycle Jitter | 30 ps (maximum) |
| Supply Voltage | 3.3 V |
| Operating Temperature | 0°C to 85°C |
| Spread Spectrum Modulation | Fixed at 1/2% modulation |
The output frequency range is 62.5 MHz to 350 MHz.
The crystal input frequency range is 14 MHz to 25 MHz.
The cycle-to-cycle jitter is 30 ps (maximum).
The operating temperature range is 0°C to 85°C.