The TPS7A57 is a low-noise (2.45 μV_RMS over 10-Hz to 100-kHz bandwidth), ultra-high PSRR (> 36 dB to 1 MHz), high-accuracy (1%), ultra-low-dropout (LDO) linear voltage regulator with an input range of 0.7 V to 6.0 V and an output voltage range from 0.5 V to 5.2 V. This device uses innovative circuitry to achieve wide bandwidth and high loop gain, resulting in ultra-high PSRR even with very low operational headroom [V_OpHr = (V_IN – V_OUT)]. At a high level, the device has two main primary features (the current reference and the unity-gain LDO buffer) and a few secondary features (such as the adjustable soft-start inrush control, precision enable, charge pump enable, and PG pin).

The current reference is controlled by the REF pin. This pin sets the output voltage with a single resistor.

The NR/SS pin sets the start-up time, and filters the noise generated by the reference and external set resistor.

The unity-gain LDO buffer controls the output voltage. The 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 low-noise current reference, 50 μA typical, is used in conjunction with an external resistor (R_REF) to set the output voltage. This process allows the output voltage range to be set from 0.5 V to 5.2 V. To achieve its low noise and allow for a soft-start inrush, an external capacitor, C_NR/SS (typically 4.7 μF), is placed on the NR/SS pin. When start-up is completed and the switch between REF and NR/SS is closed, the C_NR/SS capacitor is in parallel with the R_REF resistor attenuating the band-gap noise. The R_REF resistor sets the output voltage. This unity-gain LDO provides ultra-high PSRR over a wide frequency range without compromising load and line transients.

The EN pin sets the precision enable feature; a resistor divider on this pin selects the optimal input voltage at which the device starts. There are three independent undervoltage lockout (UVLO) voltages in this device: the internal fixed UVLO thresholds for the IN and BIAS rails, and the externally adjustable UVLO threshold using the EN pin.

The CP_EN pin enables or disables the internal charge pump. The TPS7A57 does not allow operation below 1.1 V without a BIAS rail. If the charge pump is disabled, a minimum operating headroom between OUT and BIAS is required.

This regulator offers current limit, thermal protection, is fully specified from –40°C to +125°C, and is offered in a 16-pin WQFN, 3-mm × 3-mm thermally efficient package.