LTC1625IS#PBF Analog Devices

LTC1625 TM No R Current Mode SENSE Synchronous Step-Down Switching Regulator DESCRIPTION FEATURES n The LTC 1625 is a synchronous step-down switching Highest Efficiency Current Mode Controller n regulator controller that drives external N-Channel power No Sense Resistor Required n MOSFETs using few external components. Current mode Stable High Current Operation n control with MOSFET V sensing eliminates the need for Dual N-Channel MOSFET Synchronous Drive DS n a sense resistor and improves efficiency. The frequency of Wide V Range: 3.7V to 36V IN n a nominal 150kHz internal oscillator can be synchronized Wide V Range: 1.19V to V OUT IN n to an external clock over a 1.5:1 frequency range. 1% 1.19V Reference n Programmable Fixed Frequency with Injection Lock TM Burst Mode operation at low load currents reduces n Very Low Drop Out Operation: 99% Duty Cycle switching losses and low dropout operation extends oper- n Forced Continuous Mode Control Pin ating time in battery-powered systems. A forced continu- n Optional Programmable Soft Start ous mode control pin can assist secondary winding n Pin Selectable Output Voltage regulation by disabling Burst Mode operation when the n Foldback Current Limit main output is lightly loaded. n Output Overvoltage Protection Fault protection is provided by foldback current limiting n Logic Controlled Micropower Shutdown: I < 30A Q and an output overvoltage comparator. An external ca- n Available in 16-Lead Narrow SSOP and SO Packages pacitor attached to the RUN/SS pin provides soft start U capability for supply sequencing. A wide supply range APPLICATIONS allows operation from 3.7V (3.9V for LTC1625I) to 36V at the input and 1.19V to V at the output. IN n Notebook and Palmtop Computers, PDAs , LTC and LT are registered trademarks of Linear Technology Corporation. n Cellular Telephones and Wireless Modems No R and Burst Mode are trademarks of Linear Technology Corporation. SENSE n Battery Chargers n Distributed Power TYPICAL APPLICATION Efficiency vs Load Current 100 V IN V = 10V IN V = 5V SYNC V 5V TO OUT IN C IN 28V + RUN/SS TK 10F C SS M1 90 30V 0.1F TG Si4410DY L1 2 V = 3.3V LTC1625 OUT 10H V OUT I SW TH C 0.22F 3.3V B R BOOST C C 80 + OUT 4.5A D1 10k D B 100F MBRS140T3 CMDSH-3 C 4.7F VCC 10V V INTV C C PROG CC 3 + 2.2nF M2 70 SGND BG Si4410DY V PGND OSENSE 1625 F01 60 0.01 0.1 1 10 LOAD CURRENT (A) Figure 1. High Efficiency Step-Down Converter 1625 TA01 1 EFFICIENCY (%) U ULTC1625 ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER I FOR ATIO (Note 1) ORDER PART Input Supply Voltage (V , TK) ................. 36V to 0.3V TOP VIEW IN NUMBER Boosted Supply Voltage (BOOST)............. 42V to 0.3V EXTV 1 16 V CC IN Boosted Driver Voltage (BOOST SW) ...... 7V to 0.3V SYNC 2 15 TK LTC1625CGN Switch Voltage (SW).....................................36V to 5V RUN/SS 3 14 SW LTC1625CS EXTV Voltage ...........................................7V to 0.3V FCB 4 13 TG LTC1625IGN CC I 5 12 I Voltage ................................................2.7V to 0.3V BOOST LTC1625IS TH TH SGND 6 11 INTV FCB, RUN/SS, SYNC Voltages .....................7V to 0.3V CC V 7 10 BG OSENSE V , V Voltages ........(INTV + 0.3V) to 0.3V OSENSE PROG CC V 8 9 PGND PROG Peak Driver Output Current < 10s (TG, BG) ............ 2A INTV Output Current ........................................ 50mA GN PACKAGE S PACKAGE CC 16-LEAD PLASTIC SSOP 16-LEAD PLASTIC SO Operating Ambient Temperature Range T = 125C, = 130C/W (GN) JMAX JA LTC1625C............................................... 0C to 70C T = 125C, = 110C/W (S) JMAX JA LTC1625I (Note 5).............................. 40C to 85C Junction Temperature (Note 2)............................. 125C Consult factory for Military grade parts. Storage Temperature Range ................ 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C ELECTRICAL CHARACTERISTICS T = 25C, V = 15V unless otherwise noted. A IN SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Main Control Loop I V Feedback Current V Pin Open, I = 1.19V (Note 3) 10 50 nA IN OSENSE PROG TH V Regulated Output Voltage I = 1.19V (Note 3) OUT TH 1.19V (Adjustable) Selected V Pin Open l 1.178 1.190 1.202 V PROG 3.3V Selected V = 0V l 3.220 3.300 3.380 V PROG 5V Selected V = INTV l 4.900 5.000 5.100 V PROG CC V Reference Voltage Line Regulation V = 3.6V to 20V, I = 1.19V (Note 3), 0.001 0.01 %/V LINEREG IN TH V Pin Open PROG V Output Voltage Load Regulation I = 2V (Note 3) l 0.020 0.2 % LOADREG TH I = 0.5V (Note 3) l 0.035 0.2 % TH V Forced Continuous Threshold V Ramping Negative l 1.16 1.19 1.22 V FCB FCB I Forced Continuous Current V = 1.19V 1 2 A FCB FCB V Output Overvoltage Lockout V Pin Open 1.24 1.28 1.32 V OVL PROG I V Input Current PROG PROG 3.3V V V = 0V 3.5 7 A OUT PROG 5V V V = 5V 3.5 7 A OUT PROG I Input DC Supply Current EXTV = 5V (Note 4) Q CC Normal Mode 500 A Shutdown V = 0V, 3.7V < V < 15V 15 30 A RUN/SS IN V RUN/SS Pin Threshold l 0.8 1.4 2 V RUN/SS I Soft Start Current Source V = 0V 1.2 2.5 4 A RUN/SS RUN/SS V Maximum Current Sense Threshold V = 1V, V Pin Open 120 150 170 mV SENSE(MAX) OSENSE PROG TG Transition Time TG t Rise Time C = 3300pF 50 150 ns R LOAD TG t Fall Time C = 3300pF 50 150 ns F LOAD 2 U WU U WWW