LTC1622 Low Input Voltage Current Mode Step-Down DC/DC Controller FEATURES DESCRIPTIO n High Efficiency The LTC 1622 is a constant frequency current mode step- n Constant Frequency 550kHz Operation down DC/DC controller providing excellent AC and DC load n V Range: 2V to 10V and line regulation. The device incorporates an accurate IN n Multiampere Output Currents undervoltage feature that shuts the LTC1622 down when TM n OPTI-LOOP Compensation Minimizes C the input voltage falls below 2V. OUT n Selectable, Burst Mode Operation The LTC1622 boasts a 1.9% output voltage accuracy and n Low Dropout Operation: 100% Duty Cycle consumes only 350m A of quiescent current. For applica- n Synchronizable up to 750kHz tions where efficiency is a prime consideration and the n Current Mode Operation for Excellent Line and Load load current varies from light to heavy, the LTC1622 can TM Transient Response be configured for Burst Mode operation. Burst Mode n Low Quiescent Current: 350m A operation enhances low current efficiency and extends n Shutdown Mode Draws Only 15m A Supply Current battery run time. Burst Mode operation is inhibited during n 1.9% Reference Accuracy synchronization or when the SYNC/MODE pin is pulled low n 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- n 1- or 2-Cell Li-Ion Powered Applications nized up to 750kHz for special applications. The high n Cellular Telephones frequency operation and the available 8-lead MSOP pack- n Wireless Modems age create a high performance solution in an extremely n Portable Computers small amount of PCB area. n Distributed 3.3V, 2.5V or 1.8V Power Systems To further maximize the life of the battery source, the n Scanners P-channel MOSFET is turned on continuously in dropout n 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. 15m A. TYPICAL APPLICATIO Efficiency vs Load Current with Burst Mode Operation Enabled V IN 2.5V TO 8.5V 100 V = 4.2V 8 IN C1 R2 10F 90 V IN 0.03 V = 3.3V IN 2 1 10V I SENSE TH 7 R1 80 PDRV Si3443DV 10k L1 V = 6V IN LTC1622 C3 4.7H V OUT 5 V = 8.4V 220pF 70 IN SYNC/MODE 2.5V D1 1.5A R3 IR10BQ015 159k 4 6 + C2 60 RUN/SS GND 47F 470pF V FB R4 6V 75k 50 3 V = 2.5V OUT R = 0.03 SENSE C1: TAIYO YUDEN CERAMIC EMK325BJ106MNT L1: MURATA LQN6C-4R7 1622 F01a C2: SANYO POSCAP 6TPA47M R2: DALE WSL-1206 0-03 40 D1: INTERNATIONAL RECTIFIER IR10BQ015 1 10 100 1000 5000 LOAD CURRENT (mA) 1622 F01b Figure 1. High Efficiency Step-Down Converter 1 EFFICIENCY (%) U ULTC1622 ABSOLUTE MAXIMUM RATINGS (Note 1) Operating Temperature Range Input Supply Voltage (V ).........................0.3V to 10V IN Commercial ............................................ 0 C to 70 C RUN/SS Voltage .......................................0.3V to 2.4V Industrial ........................................... 45 C to 85 C SYNC/MODE Voltage ................................. 0.3V to V IN Junction Temperature (Note 2)............................. 125 C SENSE Voltage .......................................... 2.4V to V IN Lead Temperature (Soldering, 10 sec).................. 300 C PDRV Peak Output Current (<10m s) ......................... 1A Storage Ambient Temperature Range ... 65 C to 150 C PACKAGE/ORDER INFORMATION ORDER PART ORDER PART TOP VIEW NUMBER NUMBER TOP VIEW SENSE 1 8 V IN LTC1622CS8 SENSE 1 8 V LTC1622CMS8 IN I PDRV 2 7 TH I 2 7 PDRV TH LTC1622IS8 V 3 6 GND FB V 3 6 GND FB RUN/SS 4 5 SYNC/MODE RUN/SS 4 5 SYNC/MODE MS8 PART MARKING MS8 PACKAGE S8 PART MARKING 8-LEAD PLASTIC MSOP S8 PACKAGE T = 125 C, q = 250 C/ W 8-LEAD PLASTIC SO JMAX JA LTDB 1622 T = 125 C, q = 150 C/ W JMAX JA 1622I Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full operating temperature range, otherwise specifications are at T = 25 C. V = 4.2V A IN SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS I Feedback Current (Note 3) V = 0.8V 10 70 nA VFB FB V Regulated Feedback Voltage (Note 3) Commercial Grade l 0.785 0.8 0.815 V FB (Note 3) Industrial Grade l 0.780 0.8 0.820 V V Output Overvoltage Lockout Referenced to Nominal V 416 25 % OVL OUT D V Reference Voltage Line Regulation V = 4.2V to 8.5V (Note 3) 0.04 0.08 %/V OSENSE IN V Output Voltage Load Regulation Measured in Servo Loop V = 0.2V to 0.625V 0.3 0.5 % LOADREG ITH Measured in Servo Loop V = 0.9V to 0.625V 0.3 0.5 % ITH I Input DC Supply Current (Note 4) S Burst Mode Inhibited V = 2.3V 450 m A IN Sleep Mode V = 0V, V = 2.4V 350 400 m A ITH SYNC/MODE Shutdown V = 0V 15 30 m A RUN/SS Shutdown V = 0V, V = V 0.1V 4 10 m A RUN/SS IN UVLO V RUN/SS Threshold Commercial Grade l 0.4 0.7 0.9 V RUN/SS Industrial Grade l 0.3 0.7 1.0 V I Soft-Start Current Source V = 0V 1 2.5 5 m A RUN/SS RUN/SS f Oscillator Frequency V = 0.8V 475 550 625 kHz OSC FB V = 0V 75 110 140 kHz FB V SYNC/MODE Threshold V Ramping Down 1 1.5 V SYNC/MODE SYNC/MODE V Undervoltage Lockout V Ramping Down l 1.55 1.92 2.3 V UVLO IN V Ramping Up 1.97 2.36 V IN 2 U W U W U WW