Two new products prove that LDOs are still vibrant and vital

The legendary low dropout regulator (LDO) has proponents, detractors, and realists. The first group uses LDOs like popcorn, sprinkling them everywhere they need a local rail; the second group decries their widespread use, due to their presumed inefficiency; and the third uses them judiciously, where they make sense. Reality is that the LDO is strong power-rail solution in the right applications, and two new products demonstrate their versatility and span.

Texas Instruments claims their TPS7A30 is industry's first -36V, 200 mA LDO (input range is -3 to -36V; output is -1.22 to -33V), targeting systems which need bipolar supply rails (such as ±15 V designs). It features extremely low output noise of 16 μVrms, with power supply rejection ratio (PSRR) of 72 dB at 1 kHz, and 55 dB from 10 to 700 kHz. Featuring 1.5% nominal accuracy over line, load, and temperature, the user-adjustable LDO is stable with a single ceramic output capacitor (>2 μF). [Note: the similar TPS7A49 is rated at up to 150 mA.]

Packaging, price, and availability: The TI LDOs are available now, in MSOP-8 PowerPAD packaging, and priced at $1.50 (1000 pieces) for the TPS7A30 and $1.10 for the TPS7A49. There is also an evaluation module, the TPS7A30_49EVM-567, available for $20.

For more information, go to http://www.ti.com/tps7A30-pr.

For low-power applications, Linear Technology Corp. (LTC) announced the LT1175, a 500 mA negative-output micropower LDO. It is offered in a high-reliability military grade, for -55°C to +125°C operating junction temperature range. Operating current is just 45 μA (quiescent) and 10 μA in shutdown mode, thus preventing voltage rise during no-load conditions.

The LT1175 accepts an input of -4.3 to -20V and is available in versions which deliver fixed -5V and adjustable -3.8 to -19.5V output, with 500 mV dropout voltage. Users can select current limits of 200, 400, 600, and 800 mA, and the LDO includes power limiting (current limit foldback), thermal shutdown, and the ability to force its output to reverse voltage without damage or latchup.

Packaging, price, and availability: The LT1175 is available now, in a variety of packages, including SOIC-8, power DD-PAK, and 3-lead SOT-223, through-hole TO-220, and 8-lead PDIP. The MP grade (-55°C to +125°C) in DD-Pak is $9.60 and the SOIC is $8.70, in 1000-piece lots.

For more information, go to http://www.linear.com/1175. ♦