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TI's New LDOs Provide Ultra-Low Noise, High Ripple Rejection for Noise-Sensitive Applications

500 mA, 1 A, 1.5 A regulators reduce system cost, development time.

The manufacturer says . . .

ChipCenter's Paul O'Shea says . . .

Texas Instruments Incorporated (TI) announced three new families of low-dropout linear regulators (LDOs) that provide low-noise, high power-supply ripple rejection (PSRR), and fast transient response for powering noise-sensitive analog circuitry such as radio-frequency (RF) receivers and transmitters, voltage-controlled oscillators (VCOs), and audio amplifiers. The new LDOs support applications with output currents of 500 mA, 1 A, and 1.5 A, such as battery-powered Bluetooth-enabled digital still cameras and personal digital assistants (PDAs), and many applications that operate from a 5/3.3 V distributed bus such as line cards and high-end audio products. Noise-sensitive applications will benefit from PSRRs of up to 53 dB at 10 kHz, the ultra-low output noise (33 µV at 100 Hz to 100 kHz), and fast transient response times. In addition, when the LDO is placed in standby mode, the power-supply current is reduced to less than 1 µA, extending battery life in portable applications. The TPS795xx, TPS796xx, and TPS786xx families are available in fixed-output voltages that are adjustable over a range of 1.2 V to 5.5 V. TI's BiCMOS production process allows TI to obtain a low dropout of 250 mV at 1 A, making the LDOs suitable for post-regulation of switching supplies. Key Features 33 µV (rms) output noise at 100 Hz to 100 kHz Up to 53 dB PSRR @ 10 kHz 0.1%/V for Output Line Regulation Less than 3 mV Load Regulation 3% overall accuracy over temperature and load Fast start-up time of 50 µs Input Voltage Range 2.7 V – 5.5 V 250 mV dropout at 1 A 1 µA supply current in Shutdown mode 265 µA supply current under full load Ceramic output capacitor About Texas Instruments Texas Instruments Incorporated provides innovative DSP and analog technologies to meet our customers' real-world signal-processing requirements. In addition to semiconductors, the company's businesses include sensors and controls, and educational and productivity solutions. TI is headquartered in Dallas, Texas, and has manufacturing, design, or sales operations in more than 25 countries. Texas Instruments Incorporated Semiconductor Group SC-03062 Literature Response Center P.O. Box 954 Santa Clara, CA 91380 Phone: 800-477-8924, ext. 4500 Web: power.ti.com/sc03062

These three new LDOs from TI are 500 mA to 1.5 A, and are targeted for low-noise analog applications such as RF circuits that are typically seen in communications equipment such as wireless base stations or audio equipment. They are an extension of the previously released TPS791xx–TPS794xx series of lower current LDOs also targeted for RF and audio applications. The earlier released products are for lower current applications more targeted to cell phones, PDAs, and wireless LAN applications. These new higher current LDOs provide a higher power-supply ripple rejection (PSRR) typically in the 50 dB range at 10 kHz, and very low noise in the 30 mV range. That performance combination will be valued particularly by RF circuit designers. Most of you know that TI is not the only company playing on this turf. It is a very competitive sand box because of the booming PDA, cell-phone, and wireless LAN markets. So with the fierce competition, TI has to offer something that sets them apart, or they will be just another me-too player. There are some companies that have as high a PSRR, which is typically in the 50 dB range at 10 kHz. These competitors may also have good noise performance, but what I found is that they are typically more expensive. I should also point out that there are some small companies that offer LDOs that are cost-competitive to TI's, but their portfolio is much less comprehensive, and that can affect your designs. The LDOs are offered in an adjustable output range from 1.2 to 5.5 V as well as fixed voltages of 1.6, 1.8, 2.5, and 3.0 V. The fixed-voltage versions also offer the benefit of not having to use a voltage divider, which requires a couple of resistors. The voltage dividers are internal to the adjustable version. All these LDOs have an enable pin that is active high, and when you send a high signal to the enable pin it turns the LDO off. Typically, the standby mode will consume less than 1 µA. Of course that also means that it has a quick turn-on. TI provides a fast start-up time because these LDOs are typically used in RF receive and transmit sections, and sometimes companies will want to use the same LDO alternately to power the receive and then the transmit section. The TPS795xx, TPS796xx, and TPS786xx are now available in volume from TI and its authorized distributors. The devices are available in a five-pin SOT223-5 package and five-pin DDPAK package. Pricing per 1,000 units of the SOT223-5 option is $0.96 for the TPS795xx, $1.04 for the TPS796xx, and $1.28 for the TPS786xx. Datasheets TPS78601 TPS79501 TPS79601

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