Texas Instruments Incorporated (TI) announced a new family of low drop-out (LDO) linear regulators with extremely low noise characteristics. The new LDOs will enable wireless manufacturers to meet radio frequency (RF) specifications with minimal noise and low power consumption, giving end users better signal quality and longer usage time. Other new families of LDOs, also announced today by TI, target battery management applications and systems based on low-current microcontrollers, such as TI's MSP430. The new LDO product families optimize TI's leadership power supply technology to enable a wide range of portable systems for more efficient operation, conserving power and prolonging battery life between charges.

TI's TPS791xx/TPS792xx LDOs offer exceptionally low noise that improves signal quality in handheld wireless systems. Output noise characteristics rated at 27 microvolts provide a high degree of accuracy in operation, while a high power supply rejection ratio (PSRR), measuring 75 decibels at 10 kilohertz (kHz), helps block system noise in communications equipment. An advanced proprietary BiCMOS process provides a low quiescent current and a very low dropout voltage of just 50 millivolts under a full 100-milliamp load, saving power.

Quick response to wake-up calls comes from a fast startup time of 50 microseconds. Fast transient response improves system accuracy when operating conditions change. The regulators are stable when used with inexpensive ceramic capacitors, serving to keep system costs down. All of these features make the TPS791/792 LDOs among the best solutions available for noise-sensitive applications, such as wireless phones, Bluetooth, PLL, modems and pagers, wireless local-area and home networks and other portable communications equipment.

The neatest thing about these LDO families is the start-up time; quoted at 50 µs in the release the practical data sheet numbers show it closer to 63 µs but, nonetheless this is fast. Combined with some nice noise figures and some excellent power-supply rejection ratios, these become must look at parts for applications of less than 100 mA loading.

The output noise levels from 100 Hz to 100 kHz are asymptotic to about the 16 µVrms level with a bypass capacitor of more than 4.7 pF. The noise reduces very little above this value and the start-up time increases, quite dramatically. The PSRR is about 70 dB at 10 kHz, a good number for parts being used in an RF environment. The TPS921xx family offers "Bar Enable" while the TPS922xx family offers "Enable" capability. Both families offer parts in SOT-23 with the fixed-output products in SOT-23-5 and adjustable parts in SOT-23-6 to allow for the additional feedback pin. The fixed voltages for the TPS921xx are 1.8 V, 3.3 V, and 4.7 V. These for the TPS922xx are 2.5 V, 2.8 V and 3.0 V.