40-V, 1.5-A linear regulator with current and temperature monitoring

June 24, 2013 // By Graham Prophet
LT3081 is a rugged 1.5-A wide input voltage range linear regulator with an extended safe operating area (SOA) compared to existing regulators, for high input-to-output voltage and high output current applications where older regulators limit the output.

The LT3081 uses a current source reference for single resistor output voltage settings and output adjustability down to zero. Output current limit can be set externally with a single resistor. This regulator architecture, combined with low millivolt regulation, enables multiple ICs to be paralleled for heat spreading and higher output current. The current from the device’s current monitor can be summed with the set current for line-drop compensation, where the output of the LT3081 increases with current to compensate for line drops.

The LT3081 achieves line and load regulation of under 2mV independent of output voltage and has an input voltage range from 1.2V to 40V. The device fits applications requiring multiple rails. Output voltage is programmable with a single resistor from 0V to 38.5V with a 1.2V dropout. The on-chip trimmed 50 µA current reference is ±1% accurate. The regulation, transient response and output noise (30 µVrms) are independent of output voltage due to the device’s voltage follower architecture. The LT3081 is configurable as a 2-terminal current source with two resistors. Input or output capacitors for stability are optional in either linear regulator or current-source mode of operation.

The LT3081 provides several monitoring and protection functions. Current limit, accurate to ±10%, can be programmed with a single resistor. Monitor outputs provide a current output proportional to temperature (1 µA/°C) and output current (200 µA/A), allowing ground-based measurement. The current monitor can be used to compensate for cable drops. The LT3081’s internal protection circuitry includes reverse input protection, reverse-current protection, internal current limiting and thermal shutdown. A TO-220 package for high power dissipation and various surface mount packages for lower power applications are available.

The LT3081 is offered in a variety of thermally enhanced surface-mount compatible packages, including a low profile (0.75mm) 12-lead 4 x 4mm DFN, a 16-lead thermally enhanced TSSOP and a 7-lead DD-Pak; all dissipate 2W in surface mount applications with no heat sink. The LT3081 is