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UltraFast™ Digitally Programmable 5A LDO Features Analog Margining, Output Current Monitor, 85mV Dropout & 25µVRMS Noise

27th October 2010

Linear Technology (UK) Limited

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Datasheet

Linear Technology has announced the LT3071, the second in a family of digitally programmable linear regulators with the lowest dropout voltage, lowest noise and fastest transient response of any monolithic 5A LDO currently available. Dropout voltage at 5A is an ultralow 85mV. Output voltage noise at 5A is only 25µVRMS over a 10Hz to 100kHz bandwidth. The LT3071's 1MHz unity gain bandwidth, coupled with its minimum 15µF ceramic output capacitance, provides a mere 30mV of overshoot/undershoot in response to a fast 4.5A output load step, saving significant bulk capacitance, space and cost. The LT3071 is ideal for efficiently powering low voltage, high current devices such as FPGAs, DSPs, ASICs, microprocessors, sensitive communication supplies, server/storage devices, and post-buck regulation applications.

The LT3071's output voltage is digitally programmable from 0.8V to 1.8V in 50mV increments. Accuracy is tightly specified at ±1% over line, load and temperature. An analog output margining feature can adjust system output voltage over a continuous ±10% range, advantageous during system development debug. A PowerGood flag indicates if output voltage is in regulation or if the device is in UVLO, and the flag also provides an early warning indication of a thermal fault. An output current monitor sources a scaled dynamic representation of output current (IOUT/2500) that can be measured directly or terminated with a resistor and converted to voltage, allowing load conditions or power to be calculated. The LT3071's input supply voltage range is 0.95V to 3.0V and its bias supply voltage ranges from 2.2V to 3.6V. The bias supply provides gate drive to the internal NMOS pass device.

Multiple LT3071 devices can be easily paralleled for higher output current and to spread heat across a circuit board. A tracking feature can control a buck regulator powering the LT3071's input. This tracking function drives the upstream buck regulator to maintain the LT3071's input voltage at VOUT + 300mV, minimizing power dissipation. If output voltage is dynamically changed, the tracking function automatically adjusts the output voltage of the buck regulator to maintain efficiency. Internal protection circuitry includes UVLO, reverse-current protection, precision current limiting with power foldback and thermal shutdown with hysteresis.