VREF

+

-

Enable and

start-up

management

Thermal,

undervoltage, and

overcurrent

protection

EN

GND

BATT

IN

OUT

LP5952

SNVS469F – OCTOBER 2006 – REVISED DECEMBER 2015

www.ti.com

7 Detailed Description

7.1 Overview

The LP5952 is a dual-supply-rail linear regulator optimized for powering ultralow-voltage circuits from a single Li-

Ion cell or 3 cell NiMH/NiCd batteries. In a typical application, BATT is connected to the battery, and IN can be

supplied by the output of front stage DC-DC Converter. IN does not exceed BATT at any time.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Dual-Rail Supply

The LP5952 requires two different supply voltages:

•

VIN, the power input voltage, is regulated to the fixed output voltage.

•

VBATT, the bias input voltage, supplies internal circuitry.

It is important that VIN does not exceed VBATT at any time. If the device is used in the typical post-regulation

application as shown in Figure 18, the sequencing of the two power supplies is not an issue because VBATT

supplies both the DC-DC regulator and the LP5952 device. The output voltage of the DC-DC regulator takes

some time to rise up and supply the input voltage of the device. In this application VIN always ramps up more

slowly than VBATT.

If VIN is shorted to VBATT, the voltages at the two supply pins ramp up simultaneously causing no problems.

However, in applications with two independent supplies connected to the LP5952, special care must be taken to

ensure that VIN is always ≤ VBATT.

7.3.2 No-Load Stability

The LP5952 remains stable and in regulation with no external load. This is an important consideration in some

circuits, for example, CMOS RAM keep-alive applications.

7.3.3 Fast Turnon

Fast turnon is ensured by an optimized architecture allowing a fast ramp of the output voltage to reach the target

voltage while the inrush current is controlled low at 120 mA typical (for a COUT of 2.2 µF).

10

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