Electronic Design

Tiny Analog Switches Are The Seeds Of Invention

Three analog-switch ICs from Fairchild Semiconductor come with an unusual warning: Keep away from poppy-seed bagels. Housed in 1.45- by 1.2-mm MicroPak packages, the FSA4157, FSA4156, and FSA1157 could easily get lost among any stray poppy-seed crumbs (a fate that allegedly befell a Fairchild application engineer). Their small size tops a list of features tailored to suit portable, battery-powered applications.

The devices specify an on-resistance of 1.1 Ω, a level available from other analog-switch ICs but not in a package as small as the MicroPak. Previously, the MicroPak's lowest on-resistance was 5.0 Ω. In portable audio applications, the 1.1-Ω on-resistance reduces the power needed to drive a speaker.

Other audio-related parameters include an on-resistance flatness of 0.2 Ω and a total harmonic distortion of just 0.002%. The switches also provide a high 7500-V electrostatic-discharge rating. Their wide 1.65- to 5.5-V supply range simplifies component selection. With competitive offerings, multiple components may be required to cover the various supply voltages.

Along with the MicroPak, the FSA4157, FSA4156, and FSA-1157 switches come in SC-70s. Pricing starts at $0.38 each in lots of 1000.

Fairchild Semiconductor

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