QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 534 LOW VOLTAGE LDO LINEAR REGULATOR LT3150 DESCRIPTION Demonstration circuit 534 is a fast transient response, very low dropout linear regulator featuring the LT3150 linear regulator. The DC534 generates fixed output voltages of 1.2V, 1.5V, and 1.8V, and is capable of delivering 4A (max.) of output current. With the LT3150 driving external N-channel MOSFETs as source followers, the DC534 can produce very fast transient response. The proper selection of the Rds(on) of the MOSFETs allows dropout voltages below 300 mV. These capabilities, plus its ability of maintaining stable operation with ceramic output capacitors, make the DC534 voltage regulator ideally suited for low Vin to Vout applications, such as microprocessor power supplies. Design files for this circuit board are available. Call the LTC factory. Table 1. Performance Summary PARAMETER CONDITION VALUE Minimum Input Voltage 1.1V Maximum Input Voltage 10V VOUT1 VIN = 1.5V, IOUT1 = 0A to 4A 1.2V ±2% VOUT2 VIN = 1.8V, IOUT2 = 0A to 4A 1.5V ±2% VOUT3 VIN = 2.5V, IOUT3 = 0A to 1.7A 1.8V ±2% Typical Output Ripple IOUT(MAX) 10mVP–P QUICK START PROCEDURE Demonstration circuit 534 is easy to set up to evaluate the performance of the LT3150. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: 3. For oscilloscope observations, connect a BNC cable NOTE: When measuring the input or output voltage rip- 1.2V, using the Output Voltage Table on the schematic. ple, 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 VIN1 or VOUT and GND terminals. See Figure 2 for proper scope probe technique. 1. Connect the input power supply and voltmeter to the VIN1 and GND terminals on the right side of the board. 2. Connect the load and voltmeter between the VOUT and GND terminals on the right side of the board. from the oscilloscope to connector J1, located on the right side of the board. 4. Before proceeding to test, set the output voltage to 5. Apply 1.5V across VIN (to GND) with 100mA of load current. Measure VOUT; it should be 1.23V ±1% (1.218V to –1.242V). 6. Increase the load current to 4A. Measure VOUT again; it should be 1.22V ±2% (1.205V to 1.255V). When finished, return IOUT to 100mA. 7. Increase the input voltage to 1.8V. Change the jump- ers for an output voltage of 1.5V (again see the Output Voltage Table below). Measure VOUT; it should be 1.5 ±1% (1.485V to 1.515V). 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 534 LOW VOLTAGE LDO LINEAR REGULATOR 8. Increase the load current to 4A. Measure VOUT again; it should be 1.5V ±2% (1.470V to 1.530V). When finished, return IOUT to 100mA. 9. Increase the input voltage to 2.5V. Change the jump- ers for an output voltage of 1.8V (again see the Out- put Voltage Table below). Measure VOUT; it should be 1.8 ±1% (1.782V to 1.818V). 10. Increase the load current to 1.7A. Measure VOUT again; it should be 1.8V ±2% (1.764V to 1.836V). When finished, return IOUT to 100mA. Figure 1. Proper Measurement Equipment Setup GND VIN Figure 2. Measuring Input or Output Ripple 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 534 LOW VOLTAGE LDO LINEAR REGULATOR 3