LTC1875 15µA Quiescent Current 1.5A Monolithic Synchronous Step-Down Regulator UFEATURESDESCRIPTIO ■ High Efficiency: Up to 95% The LTC®1875 is a high efficiency 1.5A monolithic syn- ■ Low Quiescent Current: Only 15 µ A with No Load chronous buck regulator using a constant frequency, ■ 550kHz Constant Frequency Operation current mode architecture. Operating supply current is ■ 2.65V to 6V Input Voltage Range only 15µA with no load and drops to < 1µA in shutdown. ■ VOUT from 0.8V to VIN, IOUT to 1.5A The input supply voltage range of 2.65V to 6V makes the ■ True PLL Frequency Locking from 350kHz to 750kHz LTC1875 ideally suited for single Li-Ion battery-powered ■ Power Good Output Voltage Monitor applications. 100% duty cycle provides low dropout op- ■ Low Dropout Operation: 100% Duty Cycle eration, extending battery life in portable systems. ■ Burst Mode® or Pulse Skipping Operation The switching frequency is internally set to 550kHz, allow- ■ Current Mode Operation for Excellent Line and Load ing the use of small surface mount inductors and capaci- Transient Response tors. For noise sensitive applications, the LTC1875 can be ■ Shutdown Mode Draws < 1µA Supply Current externally synchronized from 350kHz to 750kHz. Burst ■ ±2% Output Voltage Accuracy Mode operation is inhibited during synchronization or ■ Overcurrent and Overtemperature Protected when the SYNC/MODE pin is pulled low. ■ Available in 16-Lead SSOP Package The internal synchronous switch increases efficiency and U eliminates the need for an external Schottky diode. Low APPLICATIO S output voltages are easily supported with a 0.8V feedback reference voltage. The LTC1875 is available in a 16-lead ■ Portable Computers SSOP package. ■ Portable Instruments ■ Wireless Modems , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. UTYPICAL APPLICATIOHigh Efficiency Step-Down ConverterEfficiency vs Output Load Current VIN 2.65V TO 6V 100 CIN 22µF VIN = 3.6V SV 95 IN RUN/SS PVIN 90 L1 V SYNC/MODE SWP 6.8µH 85 IN = 4.2V V LTC1875 OUT* VIN = 6V 3.3V 80 PGOOD SWN + 75 150k COUT I 47µF TH PGND EFFICIENCY (%) 70 88.7k 47pF 220pF 65 VFB Burst Mode OPERATION SGND 28.0k 60 VOUT = 3.3V L = 6.8µH 55 1875 TA01 0.1 1 10 100 1000 CIN: TAIYO YUDEN CERAMIC JMK325BJ226MM OUPUT CURRENT (mA) COUT: SANYO POSCAP 6TPA47M L1: TOKO 646CY-6R8M 1875 TA01a *VOUT CONNECTED TO VIN (MINUS SWITCH AND L1 VOLTAGE DROP) FOR 2.65V < VIN < 3.3V 1875f 1
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