LTC1436A LTC1436A-PLL/LTC1437A High Efficiency Low Noise Synchronous Step-Down Switching Regulators FEATURES DESCRIPTIO Maintains Constant Frequency at Low Output Currents The LTC 1436A/LTC1437A are synchronous step-down Programmable Fixed Frequency (PLL Lockable) switching regulator controllers that drive external Wide V Range: 3.5V to 36V Operation N-channel power MOSFETs in a phase lockable, fixed IN TM Low Minimum On-Time (300ns) for High frequency architecture. The Adaptive Power output stage Frequency, Low Duty Cycle Applications selectively drives two N-channel MOSFETs at frequencies Dual N-Channel MOSFET Synchronous Drive up to 400kHz while reducing switching losses to maintain Very Low Dropout Operation: 99% Duty Cycle high efficiencies at low output currents. Low Dropout, 0.5A Linear Regulator for CPU I/O An auxiliary 0.5A linear regulator using an external PNP or Low Noise Audio Supplies pass device provides a low noise, low dropout voltage Built-In Power-On Reset Timer source. A secondary winding feedback control pin (SFB) Programmable Soft Start guarantees regulation regardless of the load on the main Low-Battery Detector output by forcing continuous operation. Remote Output Voltage Sense Foldback Current Limiting (Optional) An additional comparator is available for use as a low- Pin Selectable Output Voltage battery detector. A power-on reset timer (POR) is included Logic Controlled Micropower Shutdown: I < 25A Q which generates a signal delayed by 65536/f (300ms CLK Output Voltages from 1.19V to 9V typically) after the output is within 5% of the regulated Available in 24-Lead Narrow SSOP and 28-Lead output voltage. Internal resistive dividers provide pin SSOP Packages selectable output voltages with remote sense capability. U APPLICATIO S The operating current level is user-programmable via an external current sense resistor. Wide input supply range Notebook and Palmtop Computers, PDAs allows operation from 3.5V to 30V (36V maximum). Cellular Telephones and Wireless Modems , LTC and LT are registered trademarks of Linear Technology Corporation. Portable Instruments Adaptive Power is a trademark of Linear Technology Corporation. Battery-Operated Devices All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 5481178, 6304066, 5929620, 6580258, DC Power Distribution Systems 5705919, 5731731 TYPICAL APPLICATIO V IN 4.5V TO 22V C V OSC IN C IN C OSC + M1 22F TGL 43pF Si4412DY RUN/SS 35V M3 C TGS SS 2 IRLML2803 0.1F SW L1 R I D SENSE TH B 4.7H 0.02 V CMDSH-3 OUT C R B C LTC1436A C 1.6V C 0.1F 10k INTV CC 510pF 5A SGND BOOST + R1 100pF C 4.7F D1 35.7k OUT + M2 100F V MBRS140T3 PROG BG Si4412DY 6.3V R2 V OSENSE PGND 2 102k + SENSE SENSE 1000pF 1436 F01 Figure 1. High Efficiency Step-Down Converter 14367afb 1 U ULTC1436A LTC1436-PLL-A/LTC1437A ABSOLUTE MAXIMUM RATINGS (Note 1) Input Supply Voltage (V ).........................36V to 0.3V AUXON, PLLIN, SFB, IN Topside Driver Supply Voltage (Boost) ......42V to 0.3V RUN/SS, LBI Voltages ..........................10V to 0.3V Switch Voltage (SW) ....................................36V to 5V Peak Driver Output Current < 10s (TGL, BG).......... 2A EXTV Voltage .........................................10V to 0.3V Peak Driver Output Current < 10s (TGS) ......... 250mA CC POR, LBO Voltages ....................................12V to 0.3V INTV Output Current ......................................... 50mA CC AUXFB Voltage ..........................................20V to 0.3V Operating Temperature Range AUXDR Voltage..........................................28V to 0.3V LTC143XAC ............................................. 0C to 70C + SENSE , SENSE , LTC143XAI/LTC143XAE (Note 8) ...... 40C to 85C V Voltages ................. INTV + 0.3V to 0.3V Junction Temperature (Note 2)............................. 125C OSENSE CC V Voltage .................................... INTV to 0.3V Storage Temperature Range ................. 65C to 150C PROG CC PLL LPF, I Voltages ...............................2.7V to 0.3V Lead Temperature (Soldering, 10 sec).................. 300C TH PACKAGE/ORDER INFORMATION TOP VIEW TOP VIEW TOP VIEW PLL LPF 1 28 PLLIN PLL LPF 1 24 PLLIN C 1 24 POR OSC C 2 27 POR OSC C 2 23 POR RUN/SS 2 23 BOOST OSC RUN/SS 3 26 BOOST RUN/SS 3 22 LBO 3 22 TGL BOOST LBO 4 25 TGL I 4 21 TGL LBI 4 21 SW TH LBI 5 24 SW SFB 5 20 SW I 5 20 TGS TH I 6 23 TGS TH SGND 6 SFB 6 19 TGS 19 V IN SFB 7 22 V IN V 7 18 V SGND 7 18 INTV PROG IN CC SGND 8 21 INTV CC V 8 17 INTV V 8 17 BG OSENSE CC PROG V 9 20 DRV PROG CC V 9 SENSE 9 16 BG 16 PGND OSENSE V 10 19 BG OSENSE + SENSE 10 15 PGND SENSE 10 15 EXTV CC NC 11 18 PGND + AUXON 11 14 EXTV SENSE 11 14 AUXDR CC SENSE 12 17 EXTV CC + AUXFB 12 13 AUXDR AUXON 12 13 AUXFB SENSE 13 16 AUXDR AUXON 14 15 AUXFB GN PACKAGE GN PACKAGE 24-LEAD PLASTIC SSOP 24-LEAD PLASTIC SSOP G PACKAGE (150 MIL SSOP) (150 MIL SSOP) 28-LEAD PLASTIC SSOP T = 125C, = 110C/W T = 125C, = 110C/W JMAX JA JMAX JA T = 125C, = 95C/W JMAX JA ORDER PART NUMBER ORDER PART NUMBER ORDER PART NUMBER LTC1436ACGN LTC1436ACGN-PLL LTC1437ACG LTC1436AIGN LTC1436AIGN-PLL LTC1437AIG LTC1436AEGN Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25C. V = 15V, V = 5V unless otherwise noted. A IN RUN/SS SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Main Control Loop I V Feedback Current V Pin Open (Note 3) 10 50 nA IN OSENSE PROG V Regulated Output Voltage (Note 3) OUT 1.19V (Adjustable) Selected V Pin Open 1.178 1.19 1.202 V PROG 3.3V Selected V = 0V 3.220 3.30 3.380 V PROG 5V Selected V = INTV 4.900 5.00 5.100 V PROG CC 14367afb 2 U W U W U WW