QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1429A HIGH EFFICIENCY, HIGH VOLTAGE 50MA SYNCHRONOUS STEP-DOWN CONVERTER LTC3642 DESCRIPTION Demonstration circuit DC1429A is a high efficiency step-down DC/DC converter featuring LTC3642 with internal high side and synchronous power switches that draws only 10µA quiescent current. It has a wide 4.5V to 45V input range and internal over voltage monitor capable of protecting the part through 60V surges. The jumper selectable output Table 1. is up to 5V. LTC3642 can supply up to 50mA load current with a programmable peak current limit that provides a simple method for optimizing efficiency in lower current applications. With no compensation required, LTC3642 is easily configured with minimal components. Gerber files for this circuit are available. Call the LTC Factory. Performance Summary (TA = 25ºC) PARAMETER CONDITION VALUE Input Voltage Output Voltage VOUT 4.5V to 45V IOUT=1mA to 50mA, VIN=10V VOUT ± 2.7% (LTC3642 Output adjustable version) VOUT ± 1.3% (LTC3642-3.3 Fixed 3.3V version) VOUT ± 1.3% (LTC3642-5 Fixed 5.0V version) Maximum Output Current 50mA DC Supply Current Active Mode, VIN=10V, IO=0A 110µA Nominal Switching Frequency Inductance=100µH, VIN=30V 350kHz QUICK START PROCEDURE The DC1429A is easy to set up to evaluate the performance of the LTC3642. For a proper measurement equipment configuration, set up the circuit according to the diagram in Figure 2. 1. Connect the input power supply to the VIN and GND terminals. Connect the load between the VOUT and GND terminals. Refer to Figure 2 for the proper measurement equipment setup. NOTE: When measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly across the VIN or VOUT and GND terminals. See the Measurement Equipment Setup diagram in Figure 1 for proper scope probe technique. To reduce the output voltage ripple further additional capacitor of 100µF can be added in parallel. 2. Before proceeding to operation, insert jumper shunt XJP1 into the OFF position and insert jumper shunt into XJP2, XJP3 or XJP4 for voltages of 1.8V, 3.3V or 5V respectively. Set the load output current to 20 mA. Please follow the procedure outlined below for proper operation. 3. Apply 6V at VIN. Measure VOUT; it should read 0V. If desired, one can measure the shutdown supply current at this point. The supply current will be about 3 µA in shutdown. 4. Turn on VOUT by changing shunt XJP1 from the OFF position to the ON position. The out- 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1429A HIGH EFFICIENCY, HIGH VOLTAGE 50MA SYNCHRONOUS STEP-DOWN CONVERTER put voltage should measure according to the voltage set by the shunt jumper in XJP2, XJP3 or XJP4. 6. Vary the VOUT load current from 1mA to 50mA, and the output voltage should be within a tolerance of ± 2.7%. 5. Vary the input voltage from 6V to 45V. Warning - If the power for the demo board is carried in long leads, the input voltage at the part could “ring”, which could affect the operation of the circuit or even exceed the maximum voltage rating of the IC. To eliminate the ringing, insert an electrolytic capacitor (for instance, Panasonic part # EEU-FC2A680L, 68µF/100V) on the pads between the input power and return terminals on the bottom of the demo board. The (greater) ESR of the electrolytic will dampen the (possible) ringing voltage due to the use of long input leads. On a normal, typical PCB, with short traces, the capacitor is not needed. Figure 1. Measuring Input or Output Ripple _ IIN _ A _ LOAD + V VIN + + VOUT _ + A _ V + _ + Figure 2. Equipment setup to test LTC3642 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1429A HIGH EFFICIENCY, HIGH VOLTAGE 50MA SYNCHRONOUS STEP-DOWN CONVERTER 3 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1429A HIGH EFFICIENCY, HIGH VOLTAGE 50MA SYNCHRONOUS STEP-DOWN CONVERTER Item Qty Reference Part Description REQUIRED CIRCUIT COMPONENTS 1 1 CIN Cap., X5R 2.2uF 50V 20% 2 1 COUT Cap., X5R 10uF 6.3V 20% 3 1 COUT1 Cap., X7R 0.1uF 16V 20% 4 1 CSS Cap., X5R 6800pF 25V 20% 5 1 L1 Inductor, 100uH 6 1 RFB1 Res., Chip 1.47M 0.06W 1% 7 1 RFB2 Res., Chip 1.18M 0.06W 1% 8 1 R1 Res., Chip 2M 0.06W 5% 9 1 U1 I.C., Volt. Reg. ADDITIONAL DEMO BOARD CIRCUIT COMPONENTS 1 0 CFFW (Opt) Cap., NPO 22pF 25V 10% 2 1 CIN1 Cap., X7R 0.22uF 100V 20% 3 1 R4 Res., Chip 4.7 Ohm 0.25W 5% 4 0 R2 (Opt) Res., Chip 715K 0.06W 1% 5 1 R3 Res/Jumper, Chip 0 Ohm 1/16W 1 AMP 6 1 RFB3 Res., Chip 475K 0.06W 1% 7 1 RFB4 Res., Chip 280K 0.06W 1% 8 0 RSET (Opt) Res., 0402 TBD HARDWARE FOR DEMO BOARD ONLY 1 6 E1,E2,E3,E4,E5,E6 Turret, Testpoint 2 1 JP1 Headers, 3 Pins 2mm Ctrs. 3 3 JP2,JP3,JP4 Jumper, 2pins 2mm Ctrs. 4 2 XJP1,XJP2 Shunt, 2mm Ctrs. 5 1 FAB, PRINTED CIRCUIT BOARD 6 1 STENCIL Manufacturer / Part # TDK C3225X5R1H225MB TDK C3216X5R0J106M AVX 0603YC104MAT AVX 04023D682MAT2A TDK VLCF5020T-101MR27 Vishay CRCW04021M47FKED Vishay CRCW04021M18FKED Vishay CRCW04022M00JNED Linear Tech. Corp. LTC3642EDD AVX 04023A220KAT2A AVX 12061C224MAT2A Vishay CRCW12064R70JNED Vishay CRCW0402715KFKED Vishay CRCW04020000Z0EA Vishay CRCW0402475KFKED Vishay CRCW0402280KFKED Mill Max 2501-2-00-80-00-00-07-0 Samtec TMM-103-02-L-S Samtec TMM-102-02-L-S Samtec 2SN-BK-G DEMO CIRCUIT 1429A STENCIL 4