Datasheet LTC1771 (Analog Devices)

LTC1771 10µA Quiescent Current High Efficiency Step-Down DC/DC Controller
U FEATURES DESCRIPTIO
■
Very Low Standby Current: 10
µ
A
The LTC®1771 is a high efficiency current mode step- ■
Available in Space-Saving 8-Lead MSOP Package
down DC/DC controller that draws as little as 10µA DC ■
Output Currents: Up to 5A
supply current to regulate the output at no load while ■
Wide VIN Range: 2.8V to 20V Operation
maintaining high efficiency for loads up to several amps. ■ VOUT Range: 1.23V to 18V The LTC1771 drives an external P-channel power MOSFET ■ High Efficiency: Over 93% Possible using a current mode, constant off-time architecture. An ■ ±2% Output Accuracy external sense resistor is used to program the operating ■ Very Low Dropout Operation: 100% Duty Cycle current level. Current mode control provides short-circuit ■ Current Mode Operation for Excellent Line and protection, excellent transient response and controlled Load Transient Response start-up behavior. Burst Mode operation enables the ■ Defeatable Burst ModeTM Operation LTC1771 to maintain high efficiency down to extremely ■ Short-Circuit Protected low currents. Shutdown mode further reduces the supply ■ Optional Programmable Soft-Start current to a mere 2µA. For low noise applications, Burst ■ Micropower Shutdown: IQ = 2µA Mode operation can be easily disabled with the MODE pin.
U
Wide input supply range of 2.8V to 18V (20V maximum)
APPLICATIO S
and 100% duty cycle operation for low dropout make the ■ Cellular Telephones and Wireless Modems LTC1771 ideal for a wide variety of battery-powered appli- ■ 1- to 4-Cell Lithium-Ion-Powered Applications cations where maximizing battery life is important. ■ Portable Instruments The LTC1771’s availability in both 8-lead MSOP and SO ■ Battery-Powered Equipment packages provides for a minimum area solution. ■ Battery Chargers , LTC and LT are registered trademarks of Linear Technology Corporation. ■ Scanners Burst Mode is a trademark of Linear Technology Corporation.
U TYPICAL APPLICATIO
VIN 4.5V TO 18V
LTC1771 Efficiency
+ R 100 SENSE 22µF 0.05Ω 25V VIN = 5V 90 VIN = 10V V M1 IN SENSE Si6447DQ RUN/SS L1 PGATE 80 15µH V V IN = 15V CSS I OUT TH LTC1771 3.3V 0.01µF RC 70 V 2A FB MODE VIN UPS5817 + C 10k OUT GND R2 150µF CC 1.64M 6.3V EFFICIENCY (%) 60 22OpF 1% R1 50 1M VOUT = 3.3V 1% RSENSE = 0.05Ω C 40 FF 1771 F01 0.1 1 10 100 1000 10000 5pF LOAD CURRENT (mA)
Figure 1. High Efficiency Step-Down Converter
1771 F01b 1