DEMO MANUAL DC290 NO-DESIGN SWITCHER LTC1877/LTC1878 Monolithic Synchronous Step-Down Regulator DESCRIPTIO Demonstration circuit DC290 is a constant-frequency voltage, by means of a jumper. The frequency is internally step-down converter using an LTC 1877 or an LTC1878 set at 550kHz or can be synchronized with an external monolithic synchronous regulator. The LTC1878 has an clock. The internal switches allow up to 600mA of output input voltage range of 2.65V < V < 6V and the LTC1877 current in an MSO8 package, providing a space-efficient IN has an input voltage range of 2.65V < V < 10V. The solution for battery-powered applications. The DC supply IN LTC1878 is optimized for low voltage operation and is current is typically only 10m A at no load and less than 1m A ideally suited for single Li-Ion cell or 3-NiCd/NiMH cell in shutdown. In switching-noise sensitive applications, TM applications. The LTC1877, with its higher voltage capa- Burst Mode operation can be inhibited by grounding the bility, is ideally suited for two Li-Ion cells or 4- to 6-NiCd/ SYNC/MODE pin with a jumper or synchronizing it with an NiMH cell applications. external clock. Gerber files for this circuit board are available. Call the LTC factory. The exclusive use of low profile surface mount compo- nents on this demo board results in a highly efficient application in a small volume. The output voltage can be , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a trademark of Linear Technology Corporation. selected from 1.5V, 2.5V, 3.3V or a user programmable PERFORmANCE SU ARY SYMBOL PARAMETER CONDITIONS JUMPER POSITION VALUE V Input Voltage Range LTC1877 All (Note 1) 2.65V to 10V IN LTC1878 All 2.65V to 6V V Output Voltage V = 5V, SYNC/MODE = 0V, RUN = 5V, I = 0mA JP1 = U, JP2 = L, JP3 = 1.5V 1.51V 0.05V OUT IN OUT V = 5V, SYNC/MODE = 0V, RUN = 5V, I = 0mA JP1 = U, JP2 = L, JP3 = 2.5V 2.52V 0.08V IN OUT V = 5V, SYNC/MODE = 0V, RUN = 5V, I = 0mA JP1 = U, JP2 = L, JP3 = 3.3V 3.33V 0.10V IN OUT V = 5V, SYNC/MODE = 0V, RUN = 5V, I = 0mA JP1 = U, JP2 = L, JP3 = OPEN (Note 2) IN OUT TYPICAL PERFORMANCE CHARACTERISTICS AND BOARD PHOTO EFFICIENCY CURVE DEMO BOARD 100 V = 3.6V IN 95 90 V = 10V IN 85 80 V = 7.2V IN 75 V = 5V IN 70 65 60 V = 3.3V OUT L = 10m H 55 Burst Mode OPERATION 50 0.1 1.0 10 100 1000 OUTPUT CURRENT (mA) 290A TA01 1 EFFICIENCY (%) U U W UW WW UDEMO MANUAL DC290 NO-DESIGN SWITCHER WWU W PERFOR A CE SU ARY SYMBOL PARAMETER CONDITIONS JUMPER POSITION VALUE I Burst Mode Operation Enabled V = 5V, SYNC/MODE = RUN = 5V, I = 0mA JP1 = JP2 = L, JP3 = 1.5V 10m A (Note 3) Q IN OUT Supply Current Pulse Skipping Mode Supply Current V = 5V, SYNC/MODE = 0V, RUN = 5V, I = 0mA JP1 = U, JP2 = L 230m A IN OUT Shutdown Current V = 5V, RUN = 0V JP2 = U <1m A IN I Maximum Output Current V = 5V, V = 2.5V (LTC1877) JP2 = L, JP3 = 1.5V 600mA OUT IN OUT = 4V, V = 2.5V (LTC1878) JP2 = L, JP3 = 1.5V 600mA V IN OUT f Operating Frequency Unsynchronized JP2 = L 550kHz OSC Synchronized JP1 = OPEN, JP2 = L 400kHz to 700kHz V Typical Output Ripple I = 600mA, V = 5V, V = 2.5V JP2 = L, JP3 = 2.5V 20mV RIPPLE OUT IN OUT P-P V Typical Load Regulation 0mA < I < 0.6A, V = 5V, SYNC/MODE = 0V JP1 = U, JP2 = L 0.3% OUT OUT IN V Synchronize Threshold Voltage All 1.2V SYNC V Minimum Shutdown Threshold Voltage All 0.4V RUN NOTE 1: JP1 and JP2 connect RUN (E1) and SYNC/MODE (E7) to either NOTE 2: Programmable via optional R7. V = 0.8V(1+ 887kW /R7) OUT GND (E3) or V (E2). When JP1 or JP2 is in the lower position (L), then IN NOTE 3: With V = 5V, the external feedback resistor contributes 0.24m A IN RUN or SYNC/MODE is connected to V . Alternatively, if JP1 or JP2 is in IN with JP3 = 1.5V selected, 0.95m A with JP3 = 2.5V selected and 1.85m A the upper position (U), then RUN or SYNC/MODE is connected to GND. If with JP3 = 3.3V selected. external sources drive RUN or SYNC/MODE, then JP1, JP2 or both must be removed. PACKAGE A D SCHE ATIC DIAGRA SM TOP VIEW RUN 1 8 PPL LPF JP2 JP1 I 2 7 SYNC/MODE TH E2 V 3 6 V FB IN V 10V (LTC1877) IN GND 4 5 SW 6V (LTC1878) C1 C *** MS8 PACKAGE R1 IN 0.01m F CER 8-LEAD PLASTIC MSOP 10k LTC187XEMS8 1 8 E1 RUN PLL LPF RUN OPTIONAL 2 7 E7 I TH SYNC/MODE SYNC/MODE R2 LTC187X 3 6 C ITH C2 V V FB IN 220pF 4 5 E6 GND SW V L1 OUT + C C ** 10m H C R3 OUT OUT1 FW 47m F 1m F 20pF 887k 6.3V CER R4 R5 R6 R7* 1M 412k 280k OPTIONAL E3 E5 GND 1.5V 2.5V 3.3V OPEN GND E4 GND JP3 * SPACE PROVIDED FOR AN OPTIONAL RESISTOR TO PROGRAM A CUSTOM OUTPUT VOLTAGE. THE OUTPUT VOLTAGE MUST NOT EXCEED 3.3V. ** C IS AN OPTIONAL CAPACITOR TO FILTER OUT VERY HIGH FREQUENCY SWITCHING NOISE. OUT1 *** C = 10F FOR LTC1877 AND C = 22F FOR LTC1878 IN IN Figure 1. LTC1877/LTC1878 Constant Frequency, High Efficiency Converter 2 W WU