DEMO MANUAL DC195 NO-DESIGN SWITCHER LTC1627 Monolithic Synchronous Step-Down Regulator DESCRIPTIO Demonstration circuit DC195 is a constant-frequency 4.5V, a charge pump bootstrapped to the SW node can be step-down converter using an LTC 1627 monolithic syn- enabled via a jumper to produce a negative supply. This chronous regulator. It provides low input voltage, high supply is used by the top driver to increase the gate efficiency conversion for cell phones and other portable overdrive of the top P-channel MOSFET, lowering its electronics operating from one or two Li-Ion cells or three R and increasing efficiency. At V < 2.5V, the DS(ON) IN to six NiCd cells. Constant 350kHz operation and up to LTC1627 shuts down and draws just a few microamperes, 500mA output capability in an SO-8 package provide a low making it ideal for single lithium-ion battery applications. noise, space-efficient solution for wireless applications. The output voltage is programmable from 1.8V to 3.3V via a second jumper. The circuit highlights the capability of the the LTC1627. Designed to work at low voltages, the input voltage (V ) IN , LTC and LT are registered trademarks of Linear Technology Corporation. can range from 2.65V to 8.5V. At input voltages lower than Burst Mode is a trademark of Linear Technology Corporation. PERFOR A CE SU ARY SYMBOL PARAMETER CONDITIONS JUMPER POSITION VALUE V Input Voltage Range JP1 = 5V 2.65V to 8.5V IN JP1 = < 5V 2.65V to 4.5V V Output Voltage See Figure 2 JP2 = 1.8V 1.82V 0.043V OUT JP2 = 2.5V 2.52V 0.06V JP2 = 2.9V 2.94V 0.07V JP2 = 3.3V 3.33V 0.079V JP2 = OPEN Note 1 I Forced Continuous Supply Current V = 5V, SYNC/FCB = 0V, RUN/SS = 2V, I = 0mA JP1 = 5V, JP2 = 3.3V 3.5mA Q IN OUT TM Burst Mode Enabled Supply Current V = 5V, SYNC/FCB = 2V, RUN/SS = 2V, I = 0mA JP1 = 5V, JP2 = 3.3V 200A IN OUT Shutdown Current V = 5V, RUN/SS = 0V, I = 0mA JP1 = 5V, JP2 = 3.3V 15A IN OUT TYPICALPERFOR A CECCHARA TERISTICSAD BOARD PHOOT S LTC1627 Efficiency Curve LTC1627 Efficiency Curve Demo Board 100 100 JP1 = 5V V = 5V IN 90 90 JP1 = < 5V V = 8.5V IN 80 80 70 70 V = 3.6V IN V = 3.3V OUT V = 2.5V OUT JP1 = 5V 60 60 1 10 100 1000 1 10 100 1000 LOAD CURRENT (mA) LOAD CURRENT (mA) 195 TPC01 195 TPC02 1 EFFICIENCY (%) EFFICIENCY (%) U UW U W WW UDEMO MANUAL DC195 NO-DESIGN SWITCHER DESCRIPTIO At low output currents, the LTC1627 automatically switches ited by grounding the SYNC/FCB pin or synchronizing it to Burst Mode operation to reduce switching losses and with an external clock. Gerber files for this circuit board maintain high operating efficiencies. In switching-noise are available. Call the LTC factory. sensitive applications, Burst Mode operation can be inhib- A ARY PERFOR CE SU SYMBOL PARAMETER CONDITIONS JUMPER POSITION VALUE I Minimum Output Current V = 5V, V = 3.3V JP1= 5V 500mA OUT IN OUT V = 3V, V = 2.5V JP1= < 5V 500mA IN OUT f Operating Frequency Unsynchronized All 350kHz OSC Synchronized All 385kHz to 525kHz V Typical Output Ripple I = 500mA, V = 5V, V = 3.3V JP1= 5V 30mV RIPPLE OUT IN OUT P-P V Typical Load Regulation 0mA < I < 0.5A, V = 5V, V = 3.3V JP1= 5V 0.5% OUT OUT IN OUT V Forced Continuous Threshold Voltage All 0.8V FCB V Synchronize Threshold Voltage All 1.2V SYNC V Minimum Shutdown Threshold Voltage All 0.4V RUN/SS Note 1: Programmable via optional R5. V = 0.8V(1 + 210k/R5) OUT PACKAGE A D SCHE ATIC DIAGRA S TOP VIEW C4 47pF I 1 8 SYNC/FCB TH RUN/SS 2 7 V DR LTC1627CS8 V 3 6 V OPTIONAL FB IN GND 4 5 SW C C1 R C S8 PACKAGE 1 8 E1 II SYNC/FCB THTH 8-LEAD PLASTIC SO SYNC/FCB C , 0.1F SS 2 7 RUN/SS V DR C IN C3 D2* C2 LTC1627 22F 0.1F 10V 0.1F 16V 3 6 E6 V V FB IN V 8.5V IN L1, 10H 4 5 E5 GND SW V OUT R6 R7 210k 10 JP1 JP1 E4 C1 V < 5V V 5V IN IN V OSENSE 0.1F + C OUT 100F E2 D1 R1 R2 R3 R4 R5** 6.3V RUN/SS BAT54S 165k 97.6k 78.7k 66.5k OPTIONAL JP2 1.8V 2.5V 3.3V OPEN 2.9V E3/E7 GND * D2 IS FOR PROTECTION AGAINST MISAPPLIED INPUT VOLTAGES WITH JP1 IN THE< 5 POSITION. DC195 SCHEMATIC ** SPACE IS PROVIDED FOR AN OPTIONAL RESISTOR TO PROGRAM A CUSTOM OUTPUT VOLTAGE. THE OUTPUT VOLTAGE MUST NOT EXCEED 3.3V. Figure 1. LTC1627 Constant Frequency, High Efficiency Converter 2 + W W U WW U W U