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Power supply selector switch has low dropout

Posted: 17 Jan 2008 ?? ?Print Version ?Bookmark and Share

Keywords:power supply selector switches? power switches? power dissipation?


Advanced Analogic Technologies Inc. (AnalogicTech) announced today two new dual input, single-output power supply selector switches with low dropout capability. Designed to operate from batteries or any power source up to 6V, the AAT4674 and AAT4674-1 integrate reverse blocking, current sensing, a programmable current limit and single control pin switching in a compact footprint.

"Designers of digital photo frames, mobile phones, STBs and many other electronic devices typically resort to discrete switches when they need to support more than one power source," said CJ Zhang, product line director for AnalogicTech. "By combining two inputs with a low 200mV drop out in a compact TSOPJW package, the AAT4674 and AAT4674-1 offer high system integrity in a smaller, more integrated solution size."

Minimizing power dissipationThe AAT4674 and AAT4674-1 operate from an input supply range of 2.5V to 6V. Both devices integrate a reverse blocking diode, current sensing, programmable current limit and single control pin switching functions.

The AAT4674 and AAT4674-1 connect the supply voltage on IN1 and IN2 to the output through very low RDS(ON)power MOSFETs that minimize voltage drops and power dissipation. The enable (EN) and select (SEL) pin voltages control the operational state of the internal power MOSFET switches. A break-before-make switchover feature minimizes output voltage droop during the transition between the input supplies on IN1 and IN2 to the output (OUT).

To power the output, both input supplies must be above the under-voltage lockout (UVLO) threshold. If both supplies are above the threshold and the device is enabled, both devices will connect the supply from IN1 to OUT when the SEL pin voltage is logic low and connect the supply from IN2 to OUT when the SEL pin voltage is logic high. If either input voltage is below the UVLO threshold on the AAT4674, then the output floats. When only one of the input voltages is above the UVLO threshold on the AAT4674-1, the device passes through the input that is above the UVLO threshold to the output.

Qualified across the -40C to 85C temperature range, the AAT4674 and AAT4674-1 are available in a Pb-free, 12-pin TSOPJW packages. The ICs sell for 73 cents in 1,000 quantities.

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