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


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


Specifications

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


Description

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.