Datasheet LTC1622 (Analog Devices)

LTC1622 Low Input Voltage Current Mode Step-Down DC/DC Controller
U FEATURES DESCRIPTIO
■
High Efficiency
The LTC®1622 is a constant frequency current mode step- ■
Constant Frequency 550kHz Operation
down DC/DC controller providing excellent AC and DC load ■
V
and line regulation. The device incorporates an accurate
IN Range: 2V to 10V
■
Multiampere Output Currents
undervoltage feature that shuts the LTC1622 down when ■
OPTI-LOOPTM Compensation Minimizes C
the input voltage falls below 2V.
OUT
■
Selectable, Burst Mode Operation
The LTC1622 boasts a ±1.9% output voltage accuracy and ■
Low Dropout Operation: 100% Duty Cycle
consumes only 350µA of quiescent current. For applica- ■ Synchronizable up to 750kHz tions where efficiency is a prime consideration and the ■ Current Mode Operation for Excellent Line and Load load current varies from light to heavy, the LTC1622 can Transient Response be configured for Burst ModeTM operation. Burst Mode ■ Low Quiescent Current: 350µA operation enhances low current efficiency and extends ■ Shutdown Mode Draws Only 15µA Supply Current battery run time. Burst Mode operation is inhibited during ■ ±1.9% Reference Accuracy synchronization or when the SYNC/MODE pin is pulled low ■ Available in 8-Lead MSOP to reduce noise and possible RF interference.
U
High constant operating frequency of 550kHz allows the
APPLICATIO S
use of a small inductor. The device can also be synchro- ■ 1- or 2-Cell Li-Ion Powered Applications nized up to 750kHz for special applications. The high ■ Cellular Telephones frequency operation and the available 8-lead MSOP pack- ■ Wireless Modems age create a high performance solution in an extremely ■ Portable Computers small amount of PCB area. ■ Distributed 3.3V, 2.5V or 1.8V Power Systems To further maximize the life of the battery source, the ■ Scanners P-channel MOSFET is turned on continuously in dropout ■ Battery-Powered Equipment (100% duty cycle). In shutdown, the device draws a mere , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode and OPTI-LOOP are a trademarks of Linear Technology Corporation. 15µA.
U TYPICAL APPLICATIO Efficiency vs Load Current with
V
Burst Mode Operation Enabled
IN 2.5V TO 8.5V 100 8 V C1 IN = 4.2V R2 10 V µF 90 IN 0.03Ω V 2 1 10V IN = 3.3V I SENSE– TH R1 7 PDRV Si3443DV 80 10k L1 VIN = 6V C3 LTC1622 4.7µH 5 VOUT 220pF SYNC/MODE 2.5V 70 VIN = 8.4V D1 R3 1.5A 4 6 IR10BQ015 159k + EFFICIENCY (%) RUN/SS C2 GND 60 47µF 470pF VFB R4 6V 75k 3 50 VOUT = 2.5V RSENSE = 0.03Ω C1: TAIYO YUDEN CERAMIC EMK325BJ106MNT L1: MURATA LQN6C-4R7 1622 F01a C2: SANYO POSCAP 6TPA47M R2: DALE WSL-1206 0-03Ω 40 D1: INTERNATIONAL RECTIFIER IR10BQ015 1 10 100 1000 5000 LOAD CURRENT (mA)
Figure 1. High Efficiency Step-Down Converter
1622 F01b 1