LP38852-ADJ Datasheet, PDF (11/31 Pages) Texas Instruments – 1.5-A Fast-Response High-Accuracy Adjustable LDO Linear Regulator

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7 Detailed Description
LP38852-ADJ
SNVS482F – JANUARY 2007 – REVISED DECEMBER 2015
7.1 Overview
The LP38852-ADJ is a high-current, low-dropout, fast-response linear regulator capable of sourcing 1.5-A load
with only 130-mV dropout. This device operates from two input voltages: V_BIAS provides voltage to internal circuit,
while V_IN is the input voltage supplying power to load. The use of an external bias rail allows the part to operate
from ultra-low V_IN voltages. The fast transient response of this device makes it suitable for powering DSP,
microcontroller cores, and post-regulators.
7.2 Functional Block Diagram
IN
BIAS
r_EN
LP38852-ADJ
Under-Voltage
Lock-Out
Thermal
Shut Down
EN
Enable
1.2V
r_SS
SS
V_REF
OUT
ADJ
I_LIMIT
0.6V
GND
7.3 Feature Description
7.3.1 Undervoltage Lockout (UVLO)
The bias voltage is monitored by a circuit which prevents the device from functioning when the bias voltage is
below the UVLO threshold of approximately 2.45 V.
As the bias voltage rises above the UVLO threshold the device control circuitry becomes active. There is
approximately 150 mV of hysteresis built into the UVLO threshold to provide noise immunity.
When the bias voltage is between the UVLO threshold and the minimum operating rating value of 3 V the device
is functional, but the operating parameters are not within the specified limits.
7.3.2 Supply Sequencing
There is no requirement for the order that V_IN or V_BIAS are applied or removed.
One practical limitation is that the soft-start circuit starts charging soft-start timing capacitor (C_SS) when both
V_BIAS rises above the UVLO threshold and the EN pin is above the V_EN(ON) threshold. If the application of V_IN is
delayed beyond this point the benefits of soft start is compromised.
In any case, the output voltage cannot be ensured until both V_IN and V_BIAS are within the range of specified
operating values.
If used in a dual-supply system where the regulator output load is returned to a negative supply, the OUT pin
must be diode clamped to ground. A Schottky diode is recommended for this diode clamp.
Copyright © 2007–2015, Texas Instruments Incorporated
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