LTC3537 2.2 MHz, 600mA Synchronous Step-Up DC/DC Converter and 100mA LDO FEATURESDESCRIPTION n High Effi ciency Step-Up DC/DC Converter and LDO The LTC®3537 combines a high effi ciency, 2.2MHz step-up DC/DC converter with an independent 100mA low dropout Step-Up n regulator (LDO). The step-up converter starts from an input
VIN: 0.68V to 5V, VOUT: 1.5V to 5.25V voltage as low as 0.68V and contains an internal 0.4Ω IOUT: 100mA at 3.3V, VIN >0.8V n switch and a 0.6Ω synchronous rectifi er that disconnects
2.2MHz Fixed Frequency Operation n from the output when disabled in shutdown.
Synchronous Rectifi er with Output Disconnect n
Burst Mode Operation (Pin Selectable) A switching frequency of 2.2MHz minimizes solution Linear LDO Regulator footprint by allowing the use of tiny, low profi le inductors n
V and ceramic capacitors. The current mode PWM design IN: 1.8V to 5.5V, VOUT: 0.6V to 5V I is internally compensated, reducing external parts count. OUT: 100mA n
100mV Dropout Voltage at 50mA Fixed frequency switching is maintained until a light load n
24dB Ripple Rejection at f current is sensed, at which point Burst Mode® operation is SW engaged to maximize effi ciency. For low noise operation, Combined Burst Mode Operation can be disabled. Anti-ring circuitry n
Power Good Indicators reduces EMI by damping the inductor in discontinuous n
Low-Battery Comparator mode. Additional features include a low shutdown current n
30μA IQ of under 1μA and thermal overload protection. n
Low Profi le 3mm × 3mm × 0.75mm Package The integrated LDO regulator provides a very low noise, APPLICATIONS programmable low dropout supply. n Wireless Microphones L, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. n Portable Medical instruments n Noise Cancelling/Portable Headsets n RF and Audio Power TYPICAL APPLICATIONEffi ciency and Power Lossvs Load Current 100 1000 2.2μH 90 R6 V SW OUTB 80 100 V 665k INB VOUTB 3.3V EFFICIENCY POWER LOSS (mW) R2 33pF 70 LBI LTC3537 ALKALINE VINL + 1.74M 0.8V LBO 10μF 60 10 R5 TO FBB 1.0M PGDB 50 1.6V PGDL V V OLDO 1μF OLDO 3V 40 POWER LOSS 1 ENLDO R4 EFFICIENCY (%) OFF ON ENBST 2.05M 30 PWM BURST MODE FBL 1μF 20 0.1 SGND PGND R1 R3 1M 511k 10 VINB, MODE = 1.8V 0 0.01 0.01 0.1 1 10 100 1000 3537 TA01a LOAD CURRENT (mA) 3537 TA01b 3537fd 1
