LDO negative regulator features rail-to-rail operation

22nd September 2015

Barney Scott

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Datasheet

Linear announces the LT3091, the latest addition to its LDO+ family, a 1.5A low dropout negative linear regulator featuring low noise, rail-to-rail operation, precision programmable current limit and a bidirectional output current monitor. The device is cable-drop compensation capable, easily paralleled for higher current or circuit board heat spreading, and configurable as a 3-terminal floating regulator.

The LT3091’s input voltage range is -1.5 to -36V. A single resistor programs the adjustable rail-to-rail output voltage from 0 to -32V and dropout voltage is only 300mV (typical at full load).

The device features a trimmed, ±1% accurate 50µA current source reference and provides ±2% output voltage tolerance over line, load and temperature. Output voltage regulation, bandwidth, transient response and output noise (18µV_RMS over a 10Hz to 100kHz bandwidth) remain independent of output voltage due to the device’s unity gain voltage-follower architecture. The LT3091 is ideal for negative logic supplies, low noise instrumentation and RF supplies, rugged industrial supplies and for post-regulating switching supplies.

The LT3091 exhibits excellent stability with a wide range of output capacitors including small, low cost ceramic capacitors. It is stable with a minimum 10µF output capacitor. A single resistor adjusts the precision programmable current limit. The device’s bipolar current monitor either sources or sinks a current proportional to output current, useful for system monitoring. The LT3091’s bidirectional shutdown capability allows the device to operate with either positive or negative logic levels. In addition, the LT3091’s accurate shutdown thresholds enable a programmable UVLO threshold for either the regulator’s input supply or a positive system supply voltage.

Internal protection circuitry for the IC includes a precision current limit with foldback and thermal shutdown with hysteresis. In bipolar supply applications where the regulator’s load returns to a positive supply, the OUT pin can be pulled above GND up to 34V and will still allow the LT3091 to safely start up.

The LT3091 is available in a 3x4x0.75mm 14-lead DFN and a 16-lead TSSOP package, both with backside thermal pads. Additionally, the device is offered in the TO-220-7 and DD-Pak-7 power packages. E- and I-grade operating junction temperature is -40 to +125°C, H grade is -40 to +150°C, and the MP grade is specified over the widest operating range from -55 to +150°C. 1000-piece pricing for the E-grade version starts at $2.87 each, and devices are available from stock.