36V, 800mA linear regulator with wide SOA & monitor outputs

February 05, 2016 // By Graham Prophet
LT3089 is a rugged 800mA wide input voltage range linear regulator with usability, monitoring and protection features. The device has an extended safe operating area (SOA) compared to existing regulators, suiting it to high input-to-output voltage and high output current applications where older regulators limit the output.

The device uses a current source reference for single resistor output voltage settings and output adjustability down to 0V. Output current limit can be set externally with a single resistor. This regulator architecture, combined with low millivolt line and load 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 LT3089 increases its current to compensate for line drops.

Line and load regulation is under 2mV, independent of output voltage, over an input voltage range from 1.2V to 36V. The device fits well in applications requiring multiple rails. Output voltage is programmable with a single resistor from 0V to 34.5V with a 1.2V dropout. The on-chip trimmed 50 µA current reference is ±1% accurate. The regulation, transient response and output noise (27 µVRMS) are independent of output voltage due to the device’s voltage follower architecture. The LT3089 is configurable as a 2-terminal current source using two resistors. Input or output capacitors for stability are optional in either linear regulator mode or current-source mode of operation.

Monitoring and protection functions include current limit, that 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 LT3089’s internal protection circuitry includes reverse input protection, reverse-current protection, internal current limiting and thermal shutdown.

The LT3089 comes in a variety of thermally enhanced surface-mount compatible packages, including a low profile (0.75 mm) 12-lead 4 x 4 mm DFN, a 16-lead thermally enhanced TSSOP and a 7-lead DD-Pak; all dissipate 2W in surface mount applications with no heat sink. A range of grades/temperature ranges is available: pricing starts at $2.13 (1000) for the E grade (-40°C to 125°C).

Linear Technology; www.linear.com/product/LT3089