DEMO MANUAL DC247 DESIGN-READY SWITCHER LTC1735 Constant Frequency Synchronous DC/DC Converter DESCRIPTIO Demonstration Circuit DC247 demonstrates a 1.6V/9A to as low as 0.8V, can be configured by modifying the notebook CPU application using the LTC 1735 switching external resistive divider. External frequency synchroniza- regulator controller. A high performance, constant fre- tion is provided, as are three modes of operation: Burst TM quency, current mode architecture generates a precise Mode operation to reduce switching losses and maintain low voltage CPU core supply. Protection features include high operating efficiencies, burst inhibit/forced continu- an externally defeatable overcurrent latchoff and internal ous mode and a pulse-skipping mode that provides con- current foldback for overload conditions. A soft-latched stant frequency operation down to 1% maximum load crowbar monitors the output voltage for overvoltage pro- currents with low quiescent current. This results in a tection. The circuit was designed for a 5V to 26V input power supply that has very high efficiency, low ripple and range but allows a 4.5V to 28V range (limited by the fast transient response. Gerber files for this circuit board external MOSFETs). Strong output drivers easily handle are available. Call the LTC factory. large power MOSFETs efficiently. Other output voltages, , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a trademark of Linear Technology Corporation. PERFOR A CE SU ARY Operating Temperature Range 0 C to 50 C PARAMETER CONDITIONS VALUE Input Voltage Range (Maximum Input Voltage Limited by External MOSFET and Input Capacitor) 4.5V to 26V Output Output Voltage 1.6V Max Output Current (Continuous, Thermally Limited) 9A Max Output Current (Peak) 10.5A Typical Output Ripple at 10MHz Bandwidth (Burst Mode Operation) I = 100mA 50mV O P-P Typical Output Ripple at 10MHz Bandwidth (Continuous) I = 5A 25mV O P-P TYPICAL PERFOR A CE CHARACTERISTICS A D BOARD PHOTO Efficiency Demo Circuit 247A 100 V = 15V IN 90 V = 5V IN 80 70 V = 24V IN 60 50 EXTV = 5V CC 40 0.01 0.1 1 10 LOAD CURRENT (A) 247 TA01 1 EFFICIENCY (%) UWU WW UW UDEMO MANUAL DC247 DESIGN-READY SWITCHER PERFOR A CE SU ARY Operating Temperature Range 0 C to 50 C PARAMETER CONDITIONS VALUE V Line Regulation 4.5V to 26V 0.002%/V IN I Load Regulation No Load to Full Rated Output 0.03% OUT I Supply Current (Typical) with No Load at 15V Input, FCB = INTV 500m A Q CC Supply Current in Shutdown (Typical), V =15V, JP2 Open 15m A IN I EXTV Pin Current, V = 5V, V = 10V, No Load, FCB = INTV 460m A EXTVCC CC EXTVCC IN CC V Run Pin Threshold (Typical) 1.3V RUN Frequency Operating Frequency (Typical), C = 47pF 270kHz OSC PACKAGE A D SCHE ATIC DIAGRA S FCB/SYNC RUN GND +V IN LTC1735CS16 JP1 E4 E3 E9 E10 BURST MODE TOP VIEW R6 RF1 JP2 OFF 4.7 LATCHOFF 680k ON C 1 16 INTV TG CC OSC CF1 RUN/SS 2 15 BOOST C + + C 0.1F IN1 IN3 C OSC1 22F 22F R8 U1 I 3 14 SW TH 47pF 30V 30V 0 1 16 M2 FCB 4 13 V C TG IN OSC FDS6680A C C SS1 B1 SGND 5 12 INTV 0.22F CC 0.1F 2 15 V 6 11 BG RUN/SS BOOST OSENSE C C2 R C1 SENSE 7 10 PGND 330pF 33k 3 14 + SENSE 8 9 EXTV I SW CC TH C C1 LTC1735 100pF L1 R S PACKAGE CS1 4 13 D1 2H 0.005 V 16-LEAD PLASTIC SO FCB V OUT IN CMDSH-3 1.6V/9A E7 5 12 R S1 SGND INTV CC 10 C1 + C4 C2 V OSNS 47pF 1F 4.7F E11 6 11 M1 R7 V BG C3 OSENSE FDS6680A 10k 47pF D2 + CO3 + CO2 1% MBRS340T3 820F 100F 7 10 SENSE PGND R3 4V 2V C R4* S1 10k 1000pF 47k 1% 8 9 + EXTV CC GND SENSE EXTV CC E2 E8 Q1* V SEL VN2222 E1 R5, 10 R1* 10k R2, 10 247 F01 *NOT INSTALLED Figure 1. Demo Board Schematic PARTS LIST REFERENCE DESIGNATOR QUANTITY PART NUMBER DESCRIPTION VENDOR TELEPHONE C1, C3 2 08055A470JAT1A 47pF 50V 5% NPO Capacitor AVX (843) 946-0362 C2 1 TACC475M010R 4.7m F 10V 20% Tantalum Capacitor AVX (207) 282-5111 C4 1 0805ZC105MAT1A 1m F 10V 20% X7R Capacitor AVX (843) 946-0362 C 1 08055A101MAT1A 100pF 50V 5% NPO Capacitor AVX (843) 946-0362 C1 C 1 08055A331MAT1A 330pF 50V 5% NPO Capacitor AVX (843) 946-0362 C2 CB1 1 08055A224KAT1A 0.22m F 50V 20% X7R Capacitor AVX (843) 946-0362 2 W WU WW U W