DC1948A Analog Devices

DEMO MANUAL DC1948A LT3090 36V, 600mA Negative Linear Regulator with Programmable Current Limit Description Demonstration circuit 1948A is a 600mA low dropout sinks a current (1mA/A) proportional to output current. negative linear regulator featuring the LT 3090. This device Built-in protection includes reverse output protection, is designed for applications requiring negative output volt- internal current limit with foldback and thermal shutdown age, high current with no heat sink, output adjustability to with hysteresis. zero and low dropout voltage. The LT3090 is offered in a 10 pin DFN package and a The LT3090 features fast transient response, high PSRR 16-lead MSOP package. and low output noise. The LT3090 supplies 600mA at a The LT3090 data sheet gives a complete description of typical dropout voltage of 300mV. Operating quiescent cur- the device, operation and application information. The data rent is nominally 1mA and drops to << 1A in shutdown. sheet should be read in conjunction with this quick start A single resistor adjusts the LT3090s precision program- guide for working on or modifying the demo circuit 1948A. mable current limit. The LT3090s positive or negative Design files for this circuit board are available at current monitor either sources a current (0.5mA/A) or DEMO MANUAL DC1948A Quick s p D Demonstration circuit 1948A is easy to set up to evalu- 4. Turn on the power at the VIN. ate the performance of the LT3090. Refer to Figure 1 for NOTE. Make sure that the VIN voltage does not exceed proper measurement equipment setup and follow the 36V. procedure below: 5. Check for the proper output voltages: NOTE. When measuring the input or output voltage NOTE. If there is no output, temporarily disconnect the ripple, care must be taken to avoid a long ground lead load to make sure that the load is not set too high or on the oscilloscope probe. Measure the input or output is shorted. voltage ripple by touching the probe tip directly across the terminals of the input or output capacitors. See 6. Once the proper output voltages are established, adjust Figure 2 for proper scope probe technique. the loads within the operating range and observe the output voltage regulation, efficiency and other param- 1. Use JP2 to set the desired output voltage. eters. 2. Put JP4 on ON position. NOTE. Make sure that the power dissipation is limited 3. With power off, connect the input power supply to VIN below the thermal limit. and GND. Figure 1. DC1948A Proper Equipment Setup Figure 2. Measuring Input or Output Ripple dc1948af 2 ure roce tart