The TPS7A94 is an ultra-low-noise (0.46 μV_RMS over 10-Hz to 100-kHz bandwidth), ultra-high PSRR (> 50 dB to 2 MHz), high-accuracy (1%), low-dropout (LDO) linear voltage regulator with an input range of 1.7 V to 5.7 V and an output voltage range from 0 V to V_IN – V_DO and is fully specified above 0.4 V_OUT. This LDO regulator uses innovative circuitry to achieve wide bandwidth and high loop gain, resulting in ultra-high PSRR even when operating under very low operational headroom (V_IN – V_OUT). At a high level, the device has two main blocks (the current reference and the unity-gain LDO buffer) and a few secondary features (such as the precision enable, current limit, and PG pin).

The current reference is controlled by the NR/SS pin. This pin sets the output voltage with a single resistor, sets the start-up time, and filters the noise generated by the reference and external set resistor.

The unity-gain LDO buffer is controlled by the OUT pin. The ultra-low-noise does not increase with output voltage and provides wideband PSRR. As such, the SNS pin is only used for remote sensing of the load.

The EN_UV pin sets the precision enable feature. Select the optimal input voltage at which the LDO starts at. There are two independent UVLO voltages in this device: the internal IN rail UVLO and the EN_UV pin.

The FB_PG pin sets the current limit and power-good (PG) features. A voltage divider on this pin programs both the current limit and the PG trip point.

An ultra-low-noise current reference (150 μA, typical) is used in conjunction with an external resistor (R_NR/SS) to set the output voltage. This process allows the output voltage range to be set from 0.4 V to (V_IN – V_DO). To achieve this ultra-low noise, an external capacitor C_NR/SS (typically 4.7 μF) is placed in parallel to the R_NR/SS resistor used to set the output voltage. The unity-gain architecture provides ultra-high PSRR over a wide frequency range without compromising load and line transients.

This regulator offers programmable current-limit, thermal protection, is fully specified from –40°C to +125°C above 0.4 V_OUT, and is offered in a thermally efficient 10-pin, 3-mm × 3-mm WSON package.