DEMO MANUAL DC094 DESIGN READY SWITCHER LTC1435 Constant Frequency Synchronous DC/DC Converter U DESCRIPTIO Demonstration Circuit 094 is a constant frequency step- This results in a power supply that has very high down (buck) regulator implemented entirely in surface efficiency, low ripple and fast transient response. At mount using the LTC 1435 switching regulator controller. low output currents the LTC1435 automatically switches TM The output voltage is programmable from 1.8V to 5V via to Burst Mode operation to reduce switching losses a jumper. The input voltage can range from 4.5V to 28V and maintain high operating efficiencies. Additionally, (limited by the external MOSFETs). The circuit highlights the supply current can be shut down to less than the capabilities of the LTC1435 which uses a current 20A with an input voltage of 10V. This feature is an mode, constant frequency architecture to switch a pair of absolute necessity to maximize battery life in portable N-channel power MOSFETs while providing 99% maxi- applications. Gerber files for this circuit board are avail- mum duty cycle. Operating efficiencies exceeding 90% able. Call the LTC factory. are obtained. , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a trademark of Linear Technology Corporation. WWU W PERFOR A CE SU ARY Operating Temperature Range 0C to 50C Input Voltage Range Maximum Input Voltage (Limited by External MOSFET and Input Capacitor) 4.5V to 28V Output Output Voltage (Jumper Selectable) 1.8V, 2.5V, 2.9V, 3.3V, 5V Maximum Output Current (Continuous) 3A Maximum Output Current (Peak) 3.5A Typical Output Ripple at 10MHz Bandwidth (Burst Mode Operation) I = 100mA 50mV O P-P Typical Output Ripple at 10MHz Bandwidth (Continuous) I = 1A 35mV O P-P V Line Regulation, 6V to 20V 0.002%/V IN I Load Regulation, No Load to Full Rated Output 1% OUT I Supply Current with No Load at 10V Input (Typical), SFB = INT V , EXT V = 5V 50A Q CC CC Supply Current in Shutdown (Typical), V = 10V 15A IN I EXT V Pin Current, V = 5V, V = 10V, No Load 650A EXTVCC CC EXTVCC IN V Run Pin Threshold (Typical) 1.3V RUN Frequency Operating Frequency (Typical), C = 68pF 170kHz OSC W U U TYPICAL PERFOR A CE CHARACTERISTICS A D BOARD PHOTO Efficiency 100 V = 10V V = 5V IN OUT SFB = INT V CC 90 80 V = 3.3V OUT 70 V = 2.5V OUT 60 50 1 10 100 1000 4000 LOAD CURRENT (mA) DM094 BP DM094 TPC01 1 EFFICIENCY (%)DEMO MANUAL DC094 DESIGN READY SWITCHER PACKAGE A D SCHE ATIC DIAGRA SM TOP VIEW C 1 16 TG OSC RUN/SS 2 15 BOOST V E4 IN E3 4.5V TO 28V I 3 14 SW RUN SFB TH E2 E1 4 13 SFB V IN INT V CC GND SGND 5 12 INT V CC JP1 V 6 11 BG C OSENSE + IN 22F C2 10 SENSE 7 PGND C OSC 35V 0.1F + 68pF 2 SENSE 8 9 EXT V CC 1 16 Q1 C TG OSC Si4412DY S PACKAGE C , 0.1F 2 15 SS 16-LEAD PLASTIC SO RUN/SS BOOST R , 10k C 3 14 I SW LTC1435CS TH C , 51pF C4 C2 4 13 D1 C L1 C R SFB U1 V SENSE IN 0.1F CMDSH-3 330pF 10H 0.033 LTC1435 5 12 E6 SGND INT V CC V + C3 OUT C1, 100pF C 6 OUT 11 + 4.7F D2 V BG 100F E7 OSENSE 16V MBRS140T3 7 10V V 10 OSENSE Q2 SENSE PGND 2 C5 SGND Si4412DY 8 9 + 1000pF SENSE EXT V CC C6 100pF R2 R3 R4 R5 R6 R1 69.8k 32.4k 24.9k 20k 11k 35.7k 1% 1% 1% 1% 1% 1% JP2A JP2B JP2C JP2D JP2E 1.8V 2.5V 2.9V 3.3V 5V E8 GND E5 EXT V CC DM 094 F01 Figure 1. LTC1435 Constant Frequency, High Efficiency Converter PARTS LIST REFERENCE DESIGNATOR QUANTITY PART NUMBER DESCRIPTION VENDOR TELEPHONE C 1 08055A331KAT1A 330pF 50V 10% NPO Chip Capacitor AVX (803) 448-9411 C C 1 08055A510KAT1A 51pF 50V 10% NPO Chip Capacitor AVX (803) 448-9411 C2 C , C 2 TPSE226M035 22F 35V 20% Tantalum Capacitor AVX (803) 448-9411 IN1 IN2 C 1 08055A680JAT1A 68pF 50V 5% NPO Chip Capacitor AVX (803) 448-9411 OSC C , C 2 TPSD107M010R0080 100F 10V 20% Tantalum Capacitor AVX (803) 448-9411 OUT1 OUT2 C1, C6 2 08055A101KAT1A 100pF 50V 10% NPO Chip Capacitor AVX (803) 448-9411 C2, C4, C 3 08055G104KAT1A 0.1F 50V 10% Y5V Chip Capacitor AVX (803) 448-9411 SS C3 1 TAJB475M016 4.7F 16V 20% Tantalum Capacitor AVX (803) 448-9411 C5 1 08055C102KAT1A 1000pF 50V 10% X7R Chip Capacitor AVX (803) 448-9411 D1 1 CMDSH-3 BVR = 30V Schottky Diode Central (516) 435-1110 D2 1 MBRS140T3 BVR = 40V Schottky Diode Motorola (602) 244-3576 E1 to E8 8 1502-2 Turret Terminal Keystone (718) 956-8900 2 W W U