TPS7415, TPS7418, TPS7425, TPS7430, TPS7433

FAST-TRANSIENT-RESPONSE USING SMALL OUTPUT CAPACITOR

200-mA LOW-DROPOUT VOLTAGE REGULATORS

SLVS212 – DECEMBER 1999

11

POST OFFICE BOX 655303

APPLICATION INFORMATION

The TPS74xx family includes five voltage regulators (1.5 V, 1.8 V, 2.5 V, 3 V, and 3.3 V).

minimum load requirements

The TPS74xx family is stable even at zero load; no minimum load is required for operation.

SENSE terminal connection

The SENSE terminal must be connected to the regulator output for proper functioning of the regulator. Normally,

this connection should be as short as possible; however, the connection can be made near a critical circuit

(remote sense) to improve performance at that point. Internally, SENSE connects to a high-impedance

wide-bandwidth amplifier through a resistor-divider network and noise pickup feeds through to the regulator

output. Routing the SENSE connection to minimize/avoid noise pickup is essential. Adding an RC network

between SENSE and OUT to filter noise is not recommended because it can cause the regulator to oscillate.

external capacitor requirements

An input capacitor is not usually required; however, a ceramic bypass capacitor (1

µF or larger) improves load

transient response and noise rejection if the TPS74xx is located more than a few inches from the power supply.

A higher-capacitance electrolytic capacitor may be necessary if large (hundreds of milliamps) load transients

with fast rise times are anticipated.

Like all low dropout regulators, the TPS74xx requires an output capacitor connected between OUT and GND

to stabilize the internal control loop. The minimum recommended capacitance value is 1

µF and the ESR

(equivalent series resistance) must be at least 300 m

Ω. Solid tantalum electrolytic and aluminum electrolytic

are all suitable, provided they meet the requirements described previously.

OUT

4

1

IN

EN

GND

6

8

7

VI

1

µF

ESR

VO

1

µF

+

TPS74xx

CO

IN

5

SENSE

SENSE

Figure 20. Typical Application Circuit

regulator protection

The TPS74xx PMOS-pass transistor has a built-in back diode that conducts reverse currents when the input

voltage drops below the output voltage (e.g., during power down). Current is conducted from the output to the

input and is not internally limited. When extended reverse voltage is anticipated, external limiting may be

appropriate.

TPS7430: Not Recommended For New Designs