Programmable regulator

Linear Technology has released the LT3070, a digitally programmable linear regulator with low dropout voltage, low noise and fast transient response.

Dropout voltage at 5A is 85 mV. Output voltage noise at 5A is 25 µVRMS over a 10 Hz to 100 kHz bandwidth. The 1 MHz unity gain bandwidth, coupled with its minimum 15 µF ceramic output capacitance, provides 30 mV of overshoot/undershoot in response to a fast 4.5 A output load step.

The device is suitable for powering low-voltage, high-current devices such as FPGAs, DSPs, ASICs, microprocessors, sensitive communication supplies, server/storage devices and post-buck regulation applications.

The output voltage is digitally programmable from 0.8 to 1.8 in 50 mV increments. Accuracy is specified at ±1% over line, load and temperature. A digital margining feature can adjust system output voltage in increments of ±1%, ±3% or ±5%.

A PowerGood flag indicates if output voltage is in regulation or the device is in UVLO and the flag also provides an early warning indication of a thermal fault. The input supply voltage range is 0.95 to 3.0 and its bias supply voltage ranges from 2.2 to 3.6. The bias supply provides gate drive to the internal NMOS pass device.

Multiple devices can be paralleled for higher output current and to spread heat across a PCB. A tracking feature can control a buck regulator powering the regulator’s input. This function drives the upstream buck regulator to maintain the input voltage at VOUT + 300 mV, minimising power dissipation.

If output voltage is dynamically changed, the tracking function automatically adjusts the output voltage of the buck regulator to maintain efficiency. Circuitry includes UVLO, reverse-current protection, precision current limiting with power foldback and thermal shutdown with hysteresis.