Thursday, January 17, 2008

AnalogicTech power supply selector switch reduces system size

Designers of digital photo frames, mobile phones, set-top boxes and many other electronic devices typically resort to discrete switches when they need to support more than one power source. 

By combining two inputs with a low, 200mV dropout in a compact TSOPJW package, AnalogicTech's AAT4674 and AAT4674-1 offer high system integrity in a smaller, more integrated solution size.

The two dual input, single output power supply selector switches have low dropout capability and are 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.

The devices 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 minimise 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 minimises 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 -40 to +85C temperature range, the AAT4674 and AAT4674-1 are available in a Pb-free, 12-pin TSOPJW packages.

Contact details

For further information contact Phil Dewsbury, Advanced Analogic Technologies on +44 (0) 1189 657 763 or .

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