highpowerZONE Products for the week of August 30, 2010

Texas Instruments Says…

TPS7A30: Industry’s First -36-V, 200-mA LDO
LDOs for powering precision analog improve efficiency and accuracy in noise-sensitive applications

Texas Instruments Incorporated (TI) introduced the industry’s first -36-V low dropout regulators (LDO). The TPS7A30, paired with the positive voltage TPS7A49, provides designers with a total solution for powering precision analog applications. The devices feature ultra-high power supply rejection ratio (PSRR) performance and as low as 16uVrms of output noise. The TPS7A30 generates 200 mA, while the TPS7A49 manages 150 mA.

“Customers designing high-precision equipment need clean bipolar power rails for powering operational amplifiers, analog-to-digital converters or digital-to-analog converters,” said Sami Kiriaki, senior vice president and manager over TI’s Power Management business unit. “The TPS7A30 and TPS7A49 power for precision analog LDOs help meet that requirement with wide input voltages, lowest noise and maximum amount of transient headroom.”

EN-Genius Says…

The TPS7A30 is a 200 mA negative linear regulator with an input range from -3 V to -36 V and an adjustable output from -1.18 V to -33 V set using a conventional resistive voltage divider to be compared with the nominal on-chip -1.184 V reference. The TPS7A49 is the complementary positive linear regulator with similar, but positive, inputs and outputs.

The drop-out voltage of the TPS7A30 is a very commendable 325 mV at 200 mA load and the ground current at no load is a typical 55 µA. The lowest disable current is about 500 nA (the enable pin is CMOS-level compatible). No indication is given in the data sheet about the on-resistance of the on-chip pass device. The nominal output voltage accuracy is within ±1.5% while the overall accuracy is within ±2.5%. Line regulation is a typical 0.14% while load regulation is 0.04%. PSRR is a typical 72 dB at 120 Hz.

The most significant characteristic of the TPS7A30, particularly balanced against the PSRR, is the output noise voltage which is typically 15 µVrms with -3 V input and the reference voltage outputted, increasing to 17.5 µVrms with -6.2 V input and -5 V output (both with 10 µF of output capacitance and from 10 Hz to 100 kHz).

The input, output, noise reduction and bypass capacitors must be low ESR with ceramic X7R or X5R dielectrics preferred. Both input and output capacitors must be at least 2.2 µF for stability but 10 µF is recommended. The noise reduction and bypass capacitors are not required for stability but should be 0.01 µF for best ac and lowest noise performance.

There is a paucity of negative linear regulators and the only other 200 mA products that we know of are the LT1964 and the MAX664. The noise performance of the TPSA730 wins over them hands-down. The noise levels suggest applications in the front-ends of mobile phones as well as instrumentation and audio. The pairing with the positive regulating TPS7A49 is a no-brainer for bipolar rails in precision analog applications. The TPS7A30 is probably underpriced by about 25 cents.

The TPS7A30 and TPS7A49 are both in production in thermally-enhanced MSOP-8 priced at $1.50 and $1.10, respectively, both in 1000-piece lots.

Data Sheet TPS7A30
Data Sheet TPS7A49