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The LTC® 1474/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 TM 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-powere 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 startup 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 solu -tion.
LTC1474 Maximum Ratings
Input Supply Voltage (VIN) .........................0.3V to 20V Switch Current (SW, SENSE) .............................. 750mA Switch Voltage (SW) .......... (VIN 20V) to (VIN + 0.3V) VFB (Adjustable Versions) .........................0.3V to 12V VOUT (Fixed Versions) .............................. 0.3V to 20V LBI, LBO ....................................................0.3V to 20V RUN, SENSE ................................ 0.3V to (VIN + 0.3V) Operating Ambient Temperature Range Commercial ............................................ 0°C to 70°C Industrial ........................................... 40°C to 85°C Junction Temperature (Note 1) ........................ 125°C Storage Temperature Range ............65°C to 150°C Lead Temperature (Soldering, 10 sec................ 300°C
LTC1474 Features
* 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
LTC1474 Typical Application
* 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