There are very few negative LDOs in the market, but Linear has now offered another. The LT3015 is a 1.5A negative low dropout linear regulator featuring fast transient response, low noise and precision current limit. With its wide input voltage range of -1.8V to -30V and adjustable output voltage from -1.22V to -29.5V, the device’s common emitter NPN power transistor design requires only a single supply and enables a low dropout voltage of 310mV. Output voltage noise is only 60µV_RMS over a 10Hz to 100kHz bandwidth. The LT3015 features operating current of 1.1mA and <1µA in shutdown and quiescent current is well controlled in dropout. The LT3015 is the negative complement to one of Linear’s popular positive LDOs, the 1.5A LT1963A, and is ideal for negative logic supplies, low noise instrumentation, industrial supplies and for post-regulating switching supplies. The reference-amplifier topology of the LT3015 provides precision DC characteristics, as well as good loop stability with an extremely wide range of output capacitors, including small, low cost ceramic output capacitors. It is stable with only a 10µF output capacitor. These tiny external capacitors can be used without the necessary addition of series resistance (ESR) as is common with many other regulators. The LT3015 exhibits bidirectional shutdown capability that allows the device to operate with either positive or negative logic levels. Moreover, due to the LT3015’s high shutdown threshold accuracy, the SHDN pin can be used to set a programmable undervoltage lockout (UVLO) threshold for the regulator input supply. Internal protection circuitry for the IC includes reverse-output protection, precision current limiting (±10% over temperature) with foldback to keep the power transistor in its safe operating area, and thermal limiting with hysteresis.