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Wireless Systems Design

Low-Ohmic Switches Deliver Audio Fidelity

When dealing with audio applications, it's vital that the signal quality be protected. In space-constrained mobile applications, this obligation becomes even harder to fulfill. To help designers conquer these audio demons, three low-ohmic analog switch products have emerged. Hailing from Fairchild Semiconductor, they are the FSA4157 single-pole/double-throw (SPDT), FSA1156 normally open single-pole/single-throw (SPST NO), and the FSA1157 normally closed single-pole/single-throw (SPST NC) switches.

The devices' low On Resistance, which reaches a maximum of 1.0 to 1.35 Ω, preserves signal integrity. It also lowers the drive necessary to support audio- and signal-processing applications. The switches boast an operating voltage range from 1.65 to 5.5 V. This range should protect cell-phone batteries from the damage caused by overcharges. With their higher operating voltage, the Fairchild switches can accommodate overcharges of up to 4.6 V. Among their other features are a low THD of 0.002% typical and a low RON flatness of 0.02 Ω typical.

These analog switches incorporate features that are important to a range of customers and applications. As a result, they should make selection simpler while reducing qualification and inventory costs. With their high performance, they could even be reused in system upgrades. The switches' 350+-MHz bandwidth supports high-speed analog- and digital-signal routing in low-voltage applications. At the same time, they provide ESD protection of better than 7500 V (HBM).

The switches are available in Chip-scale MicroPak packaging. In 1000 pieces, the FSA4157 is priced at $0.45 each in six-lead SC70 or Chip-scale MicroPak. For the same quantity, the FSA1156 costs $0.38 each in six-lead SC70 or Chip-scale MicroPak. The FSA1157 is priced at $0.38 each per 1000 pieces in six-lead SC70 or Chip-scale MicroPak. The switches are available now with delivery from four weeks ARO.

Fairchild Semiconductor International
82 Running Hills Rd., South Portland, ME 04106; (207) 775-8761, FAX: (207) 775-8745,

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