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5A LDO touts lowest noise, dropout voltage

Posted: 03 Aug 2009     Print Version  Bookmark and Share

Keywords:linear regulator  LDO  buck regulator 

Linear Technology Corp. has developed a digitally programmable linear regulator that claims to deliver the lowest dropout voltage, lowest noise and fastest transient response of any monolithic 5A LDO currently available.

The LT3070 features 85mV dropout voltage and 25µVRMS output voltage noise at 5A over a 10Hz to 100kHz bandwidth. The LT3070's 1MHz unity gain bandwidth, coupled with its minimum 15µF ceramic output capacitance, provides a 30mV of overshoot/undershoot in response to a fast 4.5A output load step, saving bulk capacitance, space and cost. The LT3070 is intended 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 LT3070's output voltage is digitally programmable from 0.8V to 1.8V in 50mV increments. Accuracy is tightly specified at°1 per cent over line, load and temperature. A digital margining feature can adjust system output voltage in increments of°1 per cent,°3 per cent or°5 per cent. 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 LT3070's input supply voltage range is 0.95V to 3V 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 LT3070 devices can be easily paralleled for higher output current and to spread heat across a PCB. A tracking feature can control a buck regulator powering the LT3070's input. This tracking function drives the upstream buck regulator to maintain the LT3070's input voltage at VOUT + 300mV, minimising 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.

The LT3070 is offered in a thermally enhanced, low profile (0.75mm) 28-lead 4mm x 5mm QFN package, and both E and I grades operate from -40°C to +125°C junction temperature range.

1,000-piece pricing of the LT3070 starts at Rs.202.72 ($4.20) and Rs.231.68 ($4.80) each, respectively.

- Ismini Scouras

Get related application notes and technical articles on Power Design India.

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