LM2926/LM2927

Low Dropout Regulator with Delayed Reset

General Description

The LM2926 is a 5V, 500 mA, low dropout regulator with de-

layed reset. The microprocessor reset flag is set low by ther-

mal shutdown, short circuits, overvoltage conditions, drop-

out, and power-up. After the fault condition is corrected, the

reset flag remains low for a delay time determined by the de-

lay capacitor. Hysteresis is included in the reset circuit to

prevent oscillations, and a reset output is guaranteed down

to 3.2V supply input. A latching comparator is used to dis-

charge the delay capacitor, which guarantees a full reset

pulse even when triggered by a relatively short fault condi-

tion. A patented quiescent current reduction circuit drops the

ground pin current to 8 mA at full load when the input-output

differential is 3V or more.

Familiar PNP regulator features such as reverse battery pro-

tection, transient protection, and overvoltage shutdown are

included in the LM2926 making it suitable for use in automo-

tive and battery operated equipment.

The LM2927 is electrically identical to the LM2926 but has a

different pin-out. The LM2927 is pin-for-pin compatible with

the L4947 and TLE4260 alternatives. The LM2926 is

pin-for-pin compatible with the LM2925.

Features

n

5% output accuracy over entire operating range

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Dropout voltage typically 350 mV at 500 mA output

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Externally programmed reset delay

n

Short circuit proof

n

Reverse battery proof

n

Thermally protected

n

LM2926 is pin-for-pin compatible with the LM2925

n

P

Applications

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Battery operated equipment

n

Microprocessor-based systems

n

Portable instruments

Typical Application

Connection Diagrams and Ordering Information

DS010759-1

the regulator. This capacitor msut be rated over the same operating temperature range as the regulator. The equivalent series resistance (ESR) of this

capacitor is critical; see curve under Typical Performance Characteristics.

5–Lead TO-220

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Front View

Order Number LM2926T

See NS Package Number TO5A

5-Lead TO-220

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Front View

Order Number LM2927T

See NS Package Number TO5A

April 1998

© 1998 National Semiconductor Corporation

DS010759

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