LTC1735-1 High Efficiency Synchronous Step-Down Switching Regulator FEATURES DESCRIPTIO n Dual N-Channel MOSFET Synchronous Drive The LTC 1735-1 is a synchronous step-down switching n Programmable/Synchronizable Fixed Frequency regulator controller optimized for CPU power. OPTI-LOOP n V Range: 0.8V to 7V compensation allows the transient response to be opti- OUT n Wide V Range: 3.5V to 36V Operation mized over a wide range of output capacitance and ESR IN n Very Low Dropout Operation: 99% Duty Cycle values. TM n OPTI-LOOP Compensation Minimizes C OUT The operating frequency (synchronizable up to 500kHz) is n 1% Output Voltage Accuracy set by an external capacitor allowing maximum flexibility n Power Good Output Voltage Monitor in optimizing efficiency. The output voltage is monitored n Internal Current Foldback by a power good window comparator that indicates when n Output Overvoltage Crowbar Protection the output is within 7.5% of its programmed value, con- n Latched Short-Circuit Shutdown Timer forming to Intel Mobile CPU Specifications. with Defeat Option n Protection features include internal foldback current lim- Optional Programmable Soft-Start n iting, output overvoltage crowbar and optional short- Remote Output Voltage Sense n circuit shutdown. Soft-start is provided by an external Logic Controlled Micropower Shutdown: I < 25m A Q n capacitor that can be used to properly sequence supplies. Available in 16-Lead Narrow SSOP and SO Packages U The operating current level is user-programmable via an APPLICATIO S external current sense resistor. Wide input supply range allows operation from 3.5V to 30V (36V maximum). n Notebook and Palmtop Computers, PDAs TM n Pin defeatable Burst Mode operation provides high Power Supply for Mobile Pentium III Processor with TM efficiency at low load currents while 99% duty cycle SpeedStep Technology n provides low dropout operation. Cellular Telephones and Wireless Modems , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode and OPTI-LOOP are trademarks of Linear Technology Corporation. Pentium is a registered trademark of Intel Corporation. SpeedStep is a trademark of Intel Corporation. TYPICAL APPLICATIO V IN PGOOD 4.5V TO 24V C C : MARCON THCR70E1H226ZT IN IN 22F C : PANASONIC EEFUE06181R OUT 50V L1: PANASONIC ETQP6RZ1R20HFA C 47pF OSC 1 16 Q1 C TG R : IRC CRF2010-01-R004J CERAMIC OSC SENSE FDS6680A C 0.1F C 0.22F 2 15 B 2 SS RUN/SS BOOST L1 R 33k R C 330pF C1 SENSE 3 14 C2 1.2H LTC1735-1 0.004 V I SW OUT TH C 47pF 4 13 1.35V TO 1.60V C1 D1 PGOOD V IN 12A CMDSH-3 5 12 D2 R1 SENSE INTV CC MBRS340T3 10k + 47pF 1000pF 6 11 C + OUT 0.5% Q2, Q3 47pF SENSE BG 4.7F + 180F FDS6680A 7 10 R3 4V V PGND OSENSE 2 33.2k PANASONIC SP 8 9 47pF SGND EXTV 5V CC 1% 4 (OPTIONAL) Q4 2N7002 V = 1: V = 1.60V SEL OUT 10 R2 V = 0: V = 1.35V SEL OUT 14.3k 10 0.5% GND 1735-1 F01 Figure 1. CPU Core DC/DC Converter with Dynamic Voltage Selection from SpeedStep Enabled Processors 1 U ULTC1735-1 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 16 TG OSC NUMBER Switch Voltage (SW) ................................... 36V to 5V RUN/SS 2 15 BOOST LTC1735CGN-1 I 3 14 SW INTV , EXTV (BOOST, SW) Voltages ..... 7V to 0.3V TH CC CC LTC1735CS-1 + PGOOD 4 13 V SENSE , SENSE , IN LTC1735IGN-1 SENSE 5 12 INTV CC PGOOD Voltages................ 1.1(INTV + 0.3V) to 0.3V CC + LTC1735IS-1 SENSE 6 11 BG I , V , C Voltages .....................2.7V to 0.3V TH OSENSE OSC V 7 10 PGND OSENSE RUN/SS Voltage ....................(INTV + 0.3V) to 0.3V CC GN PART SGND 8 9 EXTV CC Peak Driver Output Current <10m s (TG, BG) .............. 3A MARKING GN PACKAGE S PACKAGE INTV Output Current ......................................... 50mA CC 16-LEAD PLASTIC SSOP 16-LEAD PLASTIC SO 17351 Operating Ambient Temperature Range T = 125 C, q = 130 C/W (GN) JMAX JA 1735I1 T = 125 C, q = 110 C/W (S) LTC1735C-1 ............................................ 0 C to 85 C JMAX JA LTC1735I-1 ........................................ 40 C to 85 C Consult factory for Military grade parts. Junction Temperature (Note 2)............................. 125 C Storage Temperature Range ................. 65 C to 150 C Lead Temperature (Soldering, 10 sec).................. 300 C 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 I Feedback Current (Note 3) 4 25 nA VOSENSE V Feedback Voltage (Note 3) l 0.792 0.8 0.808 V 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 DF Max Maximum Duty Factor In Dropout 98 99.4 % g Transconductance Amplifier g 1.3 mmho m m V Feedback Overvoltage Lockout l 0.84 0.86 0.88 V OVL I Input DC Supply Current (Note 5) Q Normal Mode 3.6V < V < 30V 450 m A IN 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 Run Pin Begin Latchoff Threshold V , Ramping Positive 4.1 4.5 V 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 OSENSE V = 4.5V RUN/SS UVLO Undervoltage Lockout Measured at V Pin (Ramping Negative) l 3.5 3.9 V IN D V Maximum Current Sense Threshold V = 0.7V l 60 75 85 mV SENSE(MAX) OSENSE + I SENSE Pins Total Source Current V = V = 0V 60 80 m A SENSE SENSE SENSE t Minimum On-Time Tested with a Square Wave (Note 4) 160 200 ns ON(MIN) 2 U WWW