TLV751 datasheet(13/29 Pages) TI1

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Band Gap

Thermal

Shutdown

UVLO

Logic

Current

Limit

GND

OUT

TLV751

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SBVS385 – DECEMBER 2019

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7 Detailed Description

7.1 Overview

The TLV751 low-dropout regulator (LDO) consumes low quiescent current and delivers excellent line and load

transient performance. These characteristics, combined with low noise and good PSRR with low dropout voltage,

make this device ideal for portable consumer applications.

This regulator offers foldback current limit, shutdown, and thermal protection. The operating junction temperature

for this device is –40°C to +125°C.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Undervoltage Lockout (UVLO)

The TLV751 uses an undervoltage lockout (UVLO) circuit that disables the output until the input voltage is

greater than the rising UVLO voltage (VUVLO). This circuit ensures that the device does not exhibit any

unpredictable behavior when the supply voltage is lower than the operational range of the internal circuitry. When

VIN is less than VUVLO, the output is connected to ground with a pulldown resistor (RPULLDOWN).

7.3.2 Shutdown

The enable pin (EN) is active high. Enable the device by forcing the EN pin to exceed VEN(HI). Turn off the device

by forcing the EN pin to drop below VEN(LO). If shutdown capability is not required, connect EN to IN.

The TLV751 has an internal pulldown MOSFET that connects an RPULLDOWN resistor to ground when the device

is disabled. The discharge time after disabling depends on the output capacitance (COUT) and the load resistance

(RL) in parallel with the pulldown resistor (RPULLDOWN). Equation 1 calculates the time constant:

τ = ( RPULLDOWN × RL) / (RPULLDOWN + RL)

(1)

7.3.3 Foldback Current Limit

The device has an internal current limit circuit that protects the regulator during transient high-load current faults

or shorting events. The current limit is a hybrid brickwall-foldback scheme. The current limit transitions from a

brickwall scheme to a foldback scheme at the foldback voltage (VFOLDBACK). In a high-load current fault with the

output voltage above VFOLDBACK, the brickwall scheme limits the output current to the current limit (ICL). When the

voltage drops below VFOLDBACK, a foldback current limit activates that scales back the current as the output

voltage approaches GND. When the output is shorted, the device supplies a typical current called the short-

circuit current limit (ISC). ICL and ISC are listed in the Electrical Characteristics table.

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