LTC1438/LTC1439 Dual High Efficiency, Low Noise, Synchronous Step-Down Switching Regulators FEATURES DESCRIPTIO The LTC 1438/LTC1439 are dual, synchronous step- Maintains Constant Frequency at Low Output down switching regulator controllers which drive external Currents N-channel power MOSFETs in a phase-lockable fixed Dual N-Channel MOSFET Synchronous Drive TM frequency architecture. The Adaptive Power output stage Programmable Fixed Frequency (PLL Lockable) selectively drives two N-channel MOSFETs at frequencies Wide V Range: 3.5V to 36V Operation IN up to 400kHz while reducing switching losses to maintain Ultrahigh Efficiency high efficiencies at low output currents. Very Low Dropout Operation: 99% Duty Cycle Low Dropout, 0.5A Linear Regulator for VPP An auxiliary 0.5A linear regulator using an external PNP Generation or Low Noise Audio Supply pass device provides a low noise, low dropout voltage Built-In Power-On Reset Timer source. A secondary winding feedback control pin (SFB1) Programmable Soft Start guarantees regulation regardless of load on the main Low-Battery Detector output by forcing continuous operation. Remote Output Voltage Sense An additional comparator is available for use as a low Foldback Current Limiting (Optional) battery detector. A power-on reset timer (POR) is included Pin Selectable Output Voltage which generates a signal delayed by 65536/f (typ CLK Logic-Controlled Micropower Shutdown: I < 30A Q 300ms) after the output is within 5% of the regulated Output Voltages from 1.19V to 9V output voltage. Internal resistive dividers provide pin Available in 28- and 36-Lead SSOP Packages selectable output voltages with remote sense capability on U one of the two outputs. APPLICATIO S The operating current levels are user-programmable via Notebook and Palmtop Computers, PDAs external current sense resistors. Wide input supply range Portable Instruments allows operation from 3.5V to 30V (36V maximum). Battery-Operated Devices , LTC and LT are registered trademarks of Linear Technology Corporation. Adaptive DC Power Distribution Systems Power is a trademark of Linear Technology Corporation. All other trademarks are the prop- erty of their respective owners. Protected by U.S. Patents including 5481178, 6304066, 5929620, 6580258, 5705919, 5731731. TYPICAL APPLICATIO V IN 5.2V TO 28V C IN D , CMDSH-3 D , CMDSH-3 + + B1 B2 4.7F 22F 16V 35V 4 BOOST 1 V V INTV BOOST 2 PROG1 IN CC M1 TGL1 TGL2 M4 L2 M3* TGS1 TGS2 M6* L1 C 10H C , 0.1F B1 B2 10H 0.1F SW2 SW1 D2 BG2 M5 D1 MBR140T3 M2 BG1 LTC1439 MBR140T3 + SENSE 2 + 1000pF SENSE 1 R SENSE2 SENSE 2 R 0.03 SENSE1 1000pF 0.03 V OSENSE2 SENSE 1 V V OUT1 OUT2 5V 3.3V I I C C C1 TH1 TH2 C2 3.5A 3.5A + C 1000pF 1000pF OUT1 RUN/SS1 C V SGND PGND RUN/SS2 OSC PROG2 220F + C OUT C R C C C R C 10V C1 C1A SS1 OSC SS2 C2 C2A 220F 220pF 10k 0.1F 56pF 0.1F 10k 470pF 10V 1438 F01 M1, M2, M4, M5: Si4412ADY M3, M6: IRLML2803 *NOT REQUIRED FOR LTC1438 BOLD LINES INDICATE HIGH CURRENT PATHS Figure 1. High Efficiency Dual 5V/3V Step-Down Converter 14389fb 1 U ULTC1438/LTC1439 ABSOLUTE AXI U RATI GS (Note 1) Input Supply Voltage (V )......................... 36V to 0.3V AUXON, PLLIN, SFB1, IN Topside Driver Voltage (BOOST 1, 2) ........ 42V to 0.3V RUN/SS1, RUN/SS2, LBI Voltages ....... 10V to 0.3V Switch Voltage (SW1, 2) ....................... V + 5V to 5V Peak Output Current < 10s (TGL1, 2, BG1, 2).......... 2A IN EXTV Voltage......................................... 10V to 0.3V Peak Output Current < 10s (TGS1, 2) ............... 250mA CC POR2, LBO Voltages ................................. 12V to 0.3V INTV Output Current ........................................ 50mA CC AUXFB Voltage ......................................... 20V to 0.3V Operating Ambient Temperature Range AUXDR Voltage......................................... 28V to 0.3V Commercial ............................................ 0C to 70C + + SENSE 1, SENSE 2, SENSE 1, SENSE 2, Extended (Note 7)............................... 40C to 85C V Voltages ................. INTV + 0.3V to 0.3V Industrial ............................................ 40C to 85C OSENSE2 CC V , V Voltages ..................... INTV to 0.3V Junction Temperature (Note 2)............................. 125C PROG1 PROG2 CC PLL LPF, I , I Voltages .................... 2.7V to 0.3V Storage Temperature Range .................. 65C to 150C TH1 TH2 Lead Temperature (Soldering, 10 sec).................. 300C PACKAGE/ORDER INFORMATION TOP VIEW ORDER ORDER 1 36 PLL LPF RUN/SS1 PART NUMBER PART NUMBER TOP VIEW + 2 35 PLLIN SENSE 1 + SENSE 1 1 28 RUN/SS1 3 34 BOOST 1 SENSE 1 SENSE 1 2 27 BOOST 1 LTC1438CG LTC1439CG 4 33 TGL1 V PROG1 V * 3 26 TGL1 PROG1 LTC1438CG-ADJ LTC1439EG 5 32 SW1 I TH1 I 4 25 SW1 TH1 LTC1438IG LTC1439IG 6 31 TGS1 POR2 POR2** 5 24 V IN LTC1438IG-ADJ LTC1439CGW C 7 30 V IN OSC C 6 23 BG1 OSC SGND 8 29 BG1 LTC1439IGW LTC1438XCG SGND 7 22 INTV CC LBI 9 28 INTV CC LBI 8 21 PGND LBO 10 27 PGND LBO 9 20 BG2 SFB1 11 26 BG2 SFB1 10 19 EXTV CC I 12 25 EXTV CC TH2 I 11 18 SW2 TH2 V 13 24 TGS2 PROG2 V 12 17 TGL2 OSENSE2 V 14 23 SW2 OSENSE2 SENSE 2 13 16 BOOST 2 SENSE 2 15 22 TGL2 + SENSE 2 14 15 RUN/SS2 + SENSE 2 16 21 BOOST 2 G PACKAGE RUN/SS2 17 20 AUXON 28-LEAD PLASTIC SSOP AUXDR 18 19 AUXFB V ON LTC1438-ADJ * OSENSE1 NC ON THE LTC1438XCG ** G PACKAGE GW PACKAGE T = 125C, = 95C/W 36-LEAD PLASTIC SSOP 36-LEAD PLASTIC SSOP JMAX JA T = 125C, = 95C/W (G) JMAX JA T = 125C, = 85C/W (GW) JMAX JA Consult factory for Military grade parts. 14389fb 2 U W U U WWW