Clock distribution ICs offer more control

Claiming a market first for precision clock management in embedded and handheld applications by providing per-channel output-enable controls, STMicroelectronics has unveiled the first six devices in a series of clock-distribution ICs.

The two-channel STCD1020, three-channel STCD1030, and four-channel STCD1040 have been designed to significantly reduce component count, as they distribute a single master clock to multiple clock domains, allowing designers to eliminate multiple individual-crystal clock sources. Fewer crystal components also benefit the design in terms of greater physical ruggedness.

With application in multi-mode devices such as cellular handsets and machine-to-machine communications, minimising power consumption is an issue. This is achieved in a variety of ways; namely through the device's individual output-enable controls, a fast startup time, 2.6mA typical quiescent current and 1 microamp standby current for the STCD1040. ST claims that the STCD1040 draws 30% less current than a discrete 4-channel solution, which requires five individual emitter-follower circuits and typically occupies over 60% more PCB area. Other advantages over discrete components are a high channel isolation that ensures low crosstalk, and low phase noise which benefits signal quality.

Designed for transmission of a single-ended sine-wave or square-wave in the range 10MHz to 52MHz, these clock-distribution ICs also integrate an AC coupling capacitor. They are capable of driving loads up to 20pF to simplify output circuitry. The standard supply voltage is 2.5V to 3.6V, while the option of 1.65V-2.75V operation allows use with low-voltage peripherals. The specified operating temperature range of -40 degrees C to +85 degrees C allows use in a wide variety of commercial and industrial applications.

The devices come in TDFN packages, with the STCD1020 offered in a 2 x 2mm 8-lead package, the STCD1030 in a 2 x 2.5mm 10-lead package, and the STCD1040 in a 2 x 3mm 12-lead package.

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