Low Quiescent Current High Efficiency Step-Down Converters

The LTC1474/LTC1475 series are high efficiency step-down converters with internal P-channel MOSFET power switches that draw only 10µA typical DC supply current at no load while maintaining output voltage. The LTC1474 uses logic-controlled shutdown while the LTC1475 features pushbutton on/off.

The low supply current coupled with Burst Mode™ operation enables the LTC1474/LTC1475 to maintain high efficiency over a wide range of loads. These features, along with their capability of 100% duty cycle for low dropout and wide input supply range, make the LTC1474/LTC1475 ideal for moderate current (up to 300mA) battery-powered applications.

The peak switch current is user-programmable with an optional sense resistor (defaults to 325mA minimum if not used) providing a simple means for optimizing the design for lower current applications. The peak current control also provides short-circuit protection and excellent start-up behavior. A low-battery detector that remains functional in shutdown is provided.

The LTC1474/LTC1475 series availability in 8-lead MSOP and SO packages and need for few additional components provide for a minimum area solution.

Applications

* Cellular Telephones and Wireless Modems

* 4mA to 20mA Current Loop Step-Down Converter

* Portable Instruments

* Battery-Operated Digital Devices

* Battery Chargers

* Inverting Converters

* Intrinsic Safety Applications

* High Efficiency: Over 92% Possible

* Very Low Standby Current: 10µA Typ

* Available in Space Saving 8-Lead MSOP Package

* Internal 1.4Ω Power Switch (VIN = 10V)

* Wide VIN Range: 3V to 18V Operation

* Very Low Dropout Operation: 100% Duty Cycle

* Low-Battery Detector Functional During Shutdown

* Programmable Current Limit with Optional Current Sense Resistor (10mA to 400mA Typ)

* Short-Circuit Protection

* Few External Components Required

* Active Low Micropower Shutdown: IQ = 6µA Typ

* Pushbutton On/Off (LTC1475 Only)

* 3.3V, 5V and Adjustable Output Versions