QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 832 DUAL OUTPUT LOW NOISE LDO REGULATORS LT3028 DESCRIPTION Demonstration circuit 832 is a dual output and dual input regulator consisting of two identical LDO linear regulators, based on the LT3028 monolithic linear regulator. Each independent input has a voltage range of 2.3V to 20V, with one output (Vout1) capable of delivering up to 500mA of output current, and the other output (Vout2) capable of delivering up to 100mA of output current. The DC supply current is typically only 50uA (for the entire IC) at no load. The LT3028 comes in either a 16lead DFN package or TSSOP package, both of which have an exposed pad on the bottom-side of the IC for better thermal performance. The DC832 comes installed with ceramic capacitors, because of the LT3028 ability of maintaining stability with ceramic output capacitors. There are ceramic bypass capacitors on each output for extra low noise performance. These features make the DC832 demo board an ideal circuit for use in batterypowered, hand-held applications or noise sensitive apGerber files for this circuit are availplications. able. Call the LTC Factory. QUICK START PROCEDURE The DC832 is easy to set up to evaluate the performance of the LT3028. For a proper measurement equipment configuration, set up the circuit according to the diagram in Figure 1. 6. Vary Vout1 load current from 0 to 500mA. Its output voltages should be within a tolerance of +/- 4%. 7. Vary Vout2 load current from 0 to 100mA. Its output voltages should be within a tolerance of +/- 4%. Please follow the procedure outlined below for proper operation. 1. Connect the input power supply to the Vin and GND terminals. Connect the loads between the Vout and GND terminals. Refer to figure 1 for the proper measurement equipment setup. 8. Observe both output voltages AC-coupled; they should measure noise voltages of less than 5mVAC each. Refer to Figure 2 for proper measurement technique. 2. Before proceeding to operation, insert jumpers JP1 and JP2 into the OFF positions, jumpers JP3 and JP4 into the voltage options of choice (2.5V, 3.3V, and 5V). 9. When finished, insert jumpers JP1 and JP2 to the OFF position(s) and disconnect the power. 3. Apply 6.5V at Vin. Measure both Vouts; they should read 0V. 4. Turn on Vout1 and Vout2 by changing jumpers JP3 and JP4 from the OFF positions to the ON positions. Both output voltages should be within a tolerance of +/- 2%. 5. Vary the input voltage from 6.5V to 20V. Both output voltages should be within +/- 3.3% tolerance. 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 a small tantalum capacitor (for instance, AVX part # TAJW106M025R) on the pads between the input power and return terminals on the bottom of the demo board. The (greater) ESR of the tantalum 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. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 832 DUAL OUTPUT LOW NOISE LDO REGULATORS Figure1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 832 DUAL OUTPUT LOW NOISE LDO REGULATORS 3