TPS7A5201RPST datasheet(9/28 Pages) TI1

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VIN

To Load

VREF

GND

TPS7A52

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SBVS295 – NOVEMBER 2019

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7.3 Feature Description

7.3.1 Voltage Regulation Features

7.3.1.1 DC Regulation

A low dropout regulator (LDO) functions as a class-B amplifier, as shown in Figure 1, in which the input signal is

the internal reference voltage (VREF). VREF is designed to have very low bandwidth at the input to the error

amplifier through the use of a low-pass filter (VNR/SS).

As such, the reference can be considered as a pure dc input signal. The low output impedance of an LDO comes

from the combination of the output capacitor and pass element. The pass element also presents a high input

impedance to the source voltage when operating as a current source. A positive LDO can only source current

because of the class-B architecture.

This device achieves a maximum of 1% output voltage accuracy primarily because of the high-precision band-

gap voltage (VBG) that creates VREF. The low dropout voltage (VDO) reduces the thermal power dissipation

required by the device to regulate the output voltage at a given current level, thereby improving system

efficiency. These features combine to make this device a good approximation of an ideal voltage source.

NOTE: VOUT = VREF × (1 + R1 / R2).

Figure 1. Simplified Regulation Circuit

7.3.1.2 AC and Transient Response

The LDO responds quickly to a transient (large-signal response) on the input supply (line transient) or the output

current (load transient) resulting from the LDO high-input impedance and low output-impedance across

frequency. This same capability also means that the LDO has a high power-supply rejection ratio (PSRR) and,

when coupled with a low internal noise-floor (Vn), the LDO approximates an ideal power supply in ac (small-

signal) and large-signal conditions.

The choice of external component values optimizes the small- and large-signal response. The NR/SS capacitor

(CNR/SS) and feed-forward capacitor (CFF) easily reduce the device noise floor and improve PSRR.

TPS7A5201RPST Datasheet(PDF) 9 Page - Texas Instruments