LTC1538-AUX/LTC1539 Dual High Efficiency, Low Noise, Synchronous Step-Down Switching Regulators FEATURES DESCRIPTION n Maintains Constant Frequency at Low Output Currents The LTC 1538-AUX/LTC1539 are dual, synchronous step- n Dual N-Channel MOSFET Synchronous Drive down switching regulator controllers which drive external n Programmable Fixed Frequency (PLL Lockable) N-channel power MOSFETs in a phase-lockable fixed TM n Wide V Range: 3.5V to 36V Operation frequency architecture. The Adaptive Power output stage IN n Ultrahigh Efficiency selectively drives two N-channel MOSFETs at frequencies n Very Low Dropout Operation: 99% Duty Cycle up to 400kHz while reducing switching losses to maintain n Low Dropout, 0.5A Linear Regulator for VPP high efficiencies at low output currents. Generation or Low Noise Audio Supply An auxiliary 0.5A linear regulator using an external PNP n Built-In Power-On Reset Timer pass device provides a low noise, low dropout voltage n Programmable Soft Start source. A secondary winding feedback control pin (SFB1) n Low-Battery Detector guarantees regulation regardless of load on the main n Remote Output Voltage Sense output by forcing continuous operation. n Foldback Current Limiting (Optional) A 5V/20mA regulator, internal 1.19V reference and an n Pin Selectable Output Voltage uncommitted comparator remain active when both con- n 5V Standby Regulator Active in Shutdown: I < 200A Q trollers are shut down. A power-on reset timer (POR) is n Output Voltages from 1.19V to 9V included which generates a signal delayed by 65536/f n Available in 28- and 36-Lead SSOP Packages CLK (typ 300ms) after the controllers output is within 5% of U the regulated first voltage. Internal resistive dividers pro- APPLICATIONS vide pin selectable output voltages with remote sense capability on one of the two outputs. n Notebook and Palmtop Computers, PDAs n Portable Instruments The operating current levels are user-programmable via n Battery-Operated Devices external current sense resistors. Wide input supply range n DC Power Distribution Systems allows operation from 3.5V to 30V (36V maximum). , LTC and LT are registered trademarks of Linear Technology Corporation. Adaptive Power is a trademark of Linear Technology Corporation. 5V STANDBY TYPICAL APPLICATION V IN 5.2V TO 28V C IN D , CMDSH-3 D , CMDSH-3 + + B1 B2 4.7F 22F 16V 35V 4 V V INTV BOOST 1 PROG1 IN CC BOOST 2 M1 TGL1 TGL2 M4 L2 M3* TGS1 TGS2 M6* L1 C 10H B1 C , 0.1F B2 10H 0.1F SW2 SW1 D2 BG2 M5 D1 MBR140T3 BG1 LTC1539 M2 MBR140T3 + SENSE 2 + 1000pF SENSE 1 R SENSE2 SENSE 2 R 0.03 SENSE1 1000pF 0.03 V OSENSE2 V SENSE 1 V OUT1 OUT2 5V 3.3V C I I TH1 TH2 C C1 C2 3.5A 3.5A + 1000pF 1000pF C OUT1 RUN/SS1 C V SGND PGND RUN/SS2 DSC PROG2 220F + C OUT C R C C C R C C1A C1 SS1 OSC SS2 C2 C2A 10V 220F 220pF 10k 0.1F 56pF 0.1F 10k 470pF 10V 1538 F01 M1, M2, M4, M5: Si4412DY M3, M6: IRLML2803 *NOT REQUIRED FOR LTC1538-AUX BOLD LINES INDICATE HIGH CURRENT PATHS Figure 1. High Efficiency Dual 5V/3V Step-Down Converter 1 U ULTC1538-AUX/LTC1539 ABSOLUTE MAXIMUM RATINGS AUXON, PLLIN, SFB1, Input Supply Voltage (V )....................... 36V to 0.3V IN RUN/SS1, RUN/SS2, LBI, Voltages ......... 10V to 0.3V Topside Driver Voltage (BOOST 1, 2) ...... 42V to 0.3V Peak Output Current < 10s (TGL1, 2, BG1, 2)......... 2A Peak Switch Voltage > 10s (SW 1, 2) ... V + 5V to 5V IN Peak Output Current < 10s (TGS1, 2) .............. 250mA EXTV Voltage........................................ 10V to 0.3V CC INTV Output Current ........................................ 50mA POR1, LBO Voltages ................................ 12V to 0.3V CC Operating Temperature Range AUXFB Voltage ........................................ 20V to 0.3V LTC1538-AUXCG/LTC1539CGW............ OC to 70C AUXDR Voltage........................................ 28V to 0.3V + + LTC1538-AUXIG/LTC1539IGW .......... 40C to 85C SENSE 1, SENSE 2, SENSE 1, SENSE 2, Junction Temperature (Note 1)............................ 125C V Voltages ................... INTV + 0.3V to 0.3V OSENSE2 CC Storage Temperature Range ................ 65C to 150C V , V Voltages .................... INTV to 0.3V PROG1 PROG2 CC Lead Temperature (Soldering, 10 sec)................. 300C PLL LPF, I , I Voltages ................... 2.7V to 0.3V TH1 TH2 PACKAGE/ORDER INFORMATION TOP VIEW ORDER ORDER TOP VIEW PART NUMBER 1 36 PLL LPF PART NUMBER RUN/SS1 + 2 35 PLLIN SENSE 1 BOOST 1 1 28 TGL1 3 BOOST 1 SENSE 1 34 RUN/SS1 2 27 SW1 LTC1538CG-AUX LTC1539CGW + 4 TGL1 V 33 PROG1 SENSE 1 3 26 V IN LTC1538IG-AUX LTC1539IGW 5 SW1 I 32 TH1 SENSE 1 4 25 BG1 6 TGS1 POR1 31 V 5 24 INTV /5V CC PROG1 7 V C 30 OSC IN I 6 23 PGND TH1 8 BG1 SGND 29 C 7 22 BG2 OSC 9 INTV /5V LBI 28 CC SGND 8 21 EXTV CC 10 PGND LBO 27 SFB1 9 20 SW2 11 BG2 SFB1 26 I 10 19 TGL2 TH2 12 EXTV I 25 TH2 CC V 11 18 BOOST 2 OSENSE2 13 TGS2 V 24 PROG2 SENSE 2 12 17 AUXON + 14 SW2 V 23 OSENSE2 SENSE 2 13 16 AUXFB 15 TGL2 SENSE 2 22 RUN/SS2 14 15 AUXDR + 16 BOOST 2 SENSE 2 21 G PACKAGE 17 AUXON RUN/SS2 20 28-LEAD PLASTIC SSOP 18 AUXFB AUXDR 19 T = 125C, = 95C/ W JMAX JA GW PACKAGE 36-LEAD PLASTIC SSOP T = 125C, = 85C/ W JMAX JA Consult factory for Military grade parts. 2 U W U W U WW