LTC1736 5-Bit Adjustable High Efficiency Synchronous Step-Down Switching Regulator FEATURES DESCRIPTIO n Dual N-Channel MOSFET Synchronous Drive The LTC 1736 is a synchronous step-down switching n Synchronizable/Programmable Fixed Frequency regulator controller optimized for CPU power. The output n Wide V Range: 3.5V to 36V Operation voltage is programmed by a 5-bit digital-to-analog con- IN n 5-Bit Digital-to-Analog V Selection: verter (DAC) that adjusts the output voltage from 0.925V OUT 0.925V to 2.00V Range with 50mV/25mV Steps to 2.00V according to Intel mobile VID specifications. The TM n OPTI-LOOP Compensation Minimizes C 0.8V reference is compatible with future microprocessor OUT n 1% Output Voltage Accuracy generations. n Power Good Output Voltage Monitor The operating frequency (synchronizable up to 500kHz) is n Active Voltage Positioning Compatible set by an external capacitor allowing maximum flexibility n Output Overvoltage Crowbar Protection in optimizing efficiency. The output voltage is monitored by n Internal Current Foldback a power good window comparator that indicates when the n Latched Short-Circuit Shutdown Timer output is within 7.5% of its programmed value. with Defeat Option n Protection features include: internal foldback current lim- Forced Continuous Control Pin n iting, output overvoltage crowbar and optional short-cir- Optional Programmable Soft-Start n cuit shutdown. Soft-start is provided by an external capaci- Remote Output Voltage Sense n tor that can be used to properly sequence supplies. The Available in 24-Lead SSOP Package U operating current level is user-programmable via an exter- APPLICATIO S nal current sense resistor. Wide input supply range allows operation from 3.5V to 30V (36V maximum). n Notebook and Palmtop Computers, PDAs TM n Power Supply for Mobile Pentium II and Pin defeatable Burst Mode operation provides high effi- Pentium III Processors ciency at low load currents. OPTI-LOOP compensation n Low Voltage Power Supplies allows the transient response to be optimized over a wide , LTC and LT are registered trademarks of Linear Technology Corporation. range of output capacitance and ESR values. OPTI-LOOP and Burst Mode are trademarks of Linear Technology Corporation. Pentium is a registered trademark of Intel Corporation. TYPICAL APPLICATIO V C IN OSC 47pF 5V TO 24V C V OSC IN C IN C SS 22F/50V 0.1F M1 2 TG L1 FDS6680A R CERAMIC SENSE RUN/SS 1.2H 0.004 V OUT C C1 SW 1.35V TO 1.60V R C 330pF D 33k B 12A LTC1736 VIDV CMDSH-3 I CC C B TH + C OUT C 0.22F C2 INTV 180F/4V CC PGOOD 47pF 4 VID4 BOOST + VID3 4.7F VID2 M2 D1 VID1 BG FDS6680A MBRS340T3 C : PANASONIC EEFUEOG181R VID0 OUT 2 C : MARCON THCR70EIH226ZT SGND PGND IN L1: PANASONIC ETQP6RZIR20HFA + V SENSE SENSE OSENSE : IRC LRF2010-01-R004J R SENSE 1000pF 47pF 1736 F01 Figure 1. High Efficiency Step-Down Converter 1 U ULTC1736 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) TOP VIEW Input Supply Voltage (V ).........................36V to 0.3V ORDER PART IN Topside Driver Supply Voltage (BOOST)....42V to 0.3V C 1 24 TG NUMBER OSC RUN/SS 2 23 BOOST Switch Voltage (SW) ....................................36V to 5V LTC1736CG I 3 22 SW EXTV , VIDV , (BOOST SW) Voltages ..7V to 0.3V TH CC CC + LTC1736IG FCB 4 21 V IN SENSE , SENSE .......................... 1.1(INTV ) to 0.3V CC SGND 5 20 INTV CC FCB Voltage ............................(INTV + 0.3V) to 0.3V CC PGOOD 6 19 BG I , V , V Voltage .........................2.7V to 0.3V TH OSENSE FB SENSE 7 18 PGND RUN/SS, VID0 to VID4, PGOOD Voltages ....7V to 0.3V + SENSE 8 17 EXTV CC Peak Driver Output Current <10m s (TG, BG) .............. 3A V 9 16 VIDV CC FB INTV Output Current ......................................... 50mA CC V 10 15 VID4 OSENSE Operating Ambient Temperature Range VID0 11 14 VID3 LTC1736C ............................................... 0 C to 85 C VID1 12 13 VID2 LTC1736I............................................ 40 C to 85 C G PACKAGE Junction Temperature (Note 2)............................. 125 C 24-LEAD PLASTIC SSOP T = 125 C, q = 110 C/W JMAX JA Storage Temperature Range ................. 65 C to 150 C Lead Temperature (Soldering, 10 sec).................. 300 C Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full operating temperature range, otherwise specifications are at T = 25 C. V = 15V, V = 5V unless otherwise noted. A IN RUN/SS SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Main Control Loop V Output Voltage Set Accuracy (Note 3) See Table 1 l 1% OSENSE D V Reference Voltage Line Regulation V = 3.6V to 30V (Note 3) 0.001 0.02 %/V LINEREG IN D V Output Voltage Load Regulation (Note 3) LOADREG Measured in Servo Loop V = 0.7V l 0.1 0.3 % ITH Measured in Servo Loop V = 2V l 0.1 0.3 % ITH g Transconductance Amplifier g 1.3 mmho m m V Forced Continuous Threshold l 0.76 0.8 0.84 V FCB I Forced Continuous Current V = 0.85V 0.17 0.3 m A FCB FCB V Feedback Overvoltage Lockout l 0.84 0.86 0.88 V OVL I Input DC Supply Current (Note 4) Q Normal Mode 450 m A Shutdown V = 0V 15 25 m A RUN/SS V Run Pin Start Threshold V , Ramping Positive 1.0 1.5 1.9 V RUN/SS RUN/SS V Run Pin Begin Latchoff Threshold V , Ramping Positive 4.1 4.5 V RUN/SS RUN/SS I Soft-Start Charge Current V = 0V 0.7 1.2 m A RUN/SS RUN/SS I RUN/SS Discharge Current Soft Short Condition, V = 0.5V, 0.5 2 4 m A SCL FB V = 4.5V RUN/SS UVLO Undervoltage Lockout Measured at V Pin (V Ramping Down) l 3.5 3.9 V IN IN D V Maximum Current Sense Threshold V = 0.7V l 60 75 85 mV SENSE(MAX) FB + I SENSE Pins Total Source Current V = V = 0.8V 60 80 m A SENSE SENSE SENSE t Minimum On-Time Tested with a Square Wave (Note 8) 160 200 ns ON(MIN) TG Transition Time: (Note 9) TG t Rise Time C = 3300pF 50 90 ns r LOAD TG t Fall Time C = 3300pF 50 90 ns f LOAD 2 U WWW