LTC1877| Datasheet

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LTC1877 High Efficiency Monolithic Synchronous Step-Down Regulator
FEATURES
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DESCRIPTIO

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High Efficiency: Up to 95% Very Low Quiescent Current: Only 10uA During Operation 600mA Output Current at VIN = 5V 2.65V to 10V Input Voltage Range 550kHz Constant Frequency Operation Synchronizable from 400kHz to 700kHz Selectable Burst ModeTM Operation or Pulse Skipping Mode No Schottky Diode Required Low Dropout Operation: 100% Duty Cycle 0.8V Reference Allows Low Output Voltages Shutdown Mode Draws < 1uA Supply Current 2% Output Voltage Accuracy Current Mode Control for Excellent Line and Load Transient Response Overcurrent and Overtemperature Protected Available in 8-Lead MSOP Package

The LTC 1877 is a high efficiency monolithic synchronous buck regulator using a constant frequency, current mode architecture. Supply current during operation is only 10uA and drops to < 1uA in shutdown. The 2.65V to 10V input voltage range makes the LTC1877 ideally suited for both single and dual Li-Ion battery-powered applications. 100% duty cycle provides low dropout operation, extending battery life in portable systems. Switching frequency is internally set at 550kHz, allowing the use of small surface mount inductors and capacitors. For noise sensitive applications the LTC1877 can be externally synchronized from 400kHz to 700kHz. Burst Mode operation is inhibited during synchronization or when the SYNC/MODE pin is pulled low, preventing low frequency ripple from interfering with audio circuitry. The internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode. Low output voltages are easily supported with the 0.8V feedback reference voltage. The LTC1877 is avai
lable in a space saving 8-lead MSOP package. Lower input voltage applications (less than 7V abs max) should refer to the LTC1878 data sheet.
, LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a trademark of Linear Technology Corporation.

APPLICATIO S
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Cellular Telephones Wireless Modems Personal Information Appliances Portable Instruments Distributed Power Systems Battery-Powered Equipment

TYPICAL APPLICATIO
VIN 2.65V TO 10V 7 10uF** CER 6 1 2 220pF 4 SYNC VIN RUN ITH GND VFB 3 SW LTC1877 5

Efficiency vs Output Current
100 95 90
VOUT 3.3V 47uF*** 887k

High Efficiency Step-Down Converter
10uH* 20pF

VIN = 3.6V

85

+

EFFICIENCY (%)

80 75 70 65 60 55

280k

*TOKO D62CB A920CY-100M **TAIYO-YUDEN CERAMIC LMK325BJ106MN ***SANYO POSCAP 6TPA47M VOUT CONNECTED TO VIN FOR 2.65V < VIN < 3.3V

50 0.1
1877 TA01

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VIN = 10V VIN = 7.2V VIN = 5V VOUT = 3.3V L = 10uH Burst Mode OPERATION 1.0 100 10 OUTPUT CURRENT (mA) 1000
1877 TA02

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LTC1877 DATASHEET