Electronic Design

Clock Generators Support Multiple MIPS-Family Processors

With spread-spectrum support, a clock-generator pair from PMC-Sierra supplies flexible timing and low emitted RF radiation for the company's RM5000, 7000, and 9000 lines of MIPS processors. These generators operate from 50 to 200 MHz and include a single phase-locked loop. Also, an available low-skew clock buffer provides dual 1-to-8 fanouts and can handle clock speeds of up to 200 MHz.

The CM5371 clock generator, which can be used with both the RM7000 and 5000 CPU families, delivers four single-ended low-voltage TTL outputs. It typically consumes about 360 mW. Designed for the RM9000 series of CPUs, the CM5391L generator delivers one differential low-voltage differential-signalling output and two single-ended low-voltage TTL outputs. It typically consumes just 300 mW. The CM74CB218 clock buffer works with either clock generator and consumes 425 mW.

Both generators' integrated spread-spectrum control lowers the level of electromagnetic interference generated by the high-speed clock signal. By doing so, it plays a significant role in complying with radiation emissions rules, such as Federal Communications Commission (FCC) Class B guidelines. It also reduces the amount of shielding that systems might otherwise require, lowering cost and simplifying the manufacturing process.

All three devices are available in environmentally friendly lead-free small-outline packages.The clock generators come in 20-lead packages, while the buffer is housed in a 28-lead package. The CM5371 and CM5391L cost $4.50 and $7.50 each, respectively, while the CM74CB218 buffer goes for $3.45 each, all in lots of 10,000 units.

PMC-Sierra Inc.

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