LDO adds features for monitoring, protection & cable drop compensation

December 24, 2013 // By Graham Prophet
Linear Technology's LT3086 is an addition to the LDO+ family, with features previously unavailable in linear regulators. The 40V, 2.1A low dropout linear regulator (LDO) includes current monitoring with externally settable current limit and temperature monitoring with external control of thermal limit temperature.

The device includes a programmable power good status flag, cable drop compensation and easy paralleling. The current reference in the LT308x LDO family provides regulation, independent of output voltage.

The LT3086 features a 1.4V to 40V input voltage range. A single resistor programs output voltage from 0.4V to 32V and dropout voltage is 330 mV at 2.1A. Line and load regulation is to 0.1%, independent of output voltage. The trimmed, precision 50 µA current reference is ±1% accurate, providing ±2% output voltage tolerance over line, load and temperature. Output voltage regulation, bandwidth, transient response and noise (40 µVRMS) remain independent of output voltage due to the device’s unity-gain voltage follower architecture.

Internal circuitry allows paralleling of multiple LT3086s for higher load current and heat spreading without needing external ballast resistors. Programmable cable drop compensation cancels regulation errors caused by line drops to the load. Output current and temperature monitoring, in addition to a power-good flag with programmable threshold, provide system monitoring and diagnostic/debug capability. Internal fault circuitry includes thermal shutdown and current limit with foldback. Thermal limit and current limit are externally programmable. The device’s reverse battery and reverse current protection add robustness to the end design.

The LT3086 is offered in a variety of thermally enhanced surface mount packages, including a low profile (0.75 mm) 16-lead 4 x 5 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. The LT3086 is also available in a 7-lead TO-220 power package for vertical mounting to heat sinks for higher power dissipation capability. E and I grades are specified with an operating junction temperature range of -40°C to +125°C. The MP grade is specified with an operating junction temperature range of -55°C to +125°C. Pricing starts at $3.00 (1000) for the E grade.

Linear Technology,  www.linear.com/product/LT3086