lm2927 National Semiconductor Corporation, lm2927 Datasheet

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lm2927

Manufacturer Part Number
lm2927
Description
Low Dropout Regulator With Delayed Reset
Manufacturer
National Semiconductor Corporation
Datasheet
© 1998 National Semiconductor Corporation
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.
Typical Application
*
**C
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.
Connection Diagrams and Ordering Information
Required if regulator is located far (
O
must be at least 10 µF to maintain stability. May be increased without bound to maintain regulation during transients. Locate as close as possible to
See NS Package Number TO5A
Order Number LM2926T
5–Lead TO-220
Front View
>
2") from power supply filter.
DS010759
DS010759-2
Features
n 5% output accuracy over entire operating range
n Dropout voltage typically 350 mV at 500 mA output
n 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
n Battery operated equipment
n Microprocessor-based systems
n Portable instruments
+
Product Enhancement tested
See NS Package Number TO5A
DS010759-1
Order Number LM2927T
5-Lead TO-220
Front View
www.national.com
DS010759-14
April 1998

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lm2927 Summary of contents

Page 1

... 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 ...

Page 2

Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Input Voltage Survival t = 100 Continuous Reset Output Sink Current ESD Susceptibility (Note ...

Page 3

... D JMAX A JA down. For the LM2926 and LM2927, the junction-to-ambient thermal resistance is 53˚C/W, and the junction-to-case thermal resistance is 3˚C/W. = 25˚C and represent the most likely parametric norm. Note 4: Typicals are Note 5: Limits are 100% guaranteed by production testing. ...

Page 4

Typical Performance Characteristics Supply Current DS010759-17 Dropout Voltage DS010759-20 Ripple Rejection DS010759-23 Line Transient Response DS010759-26 www.national.com (Continued) Quiescent Current DS010759-18 Output Current Limit DS010759-21 Ripple Rejection DS010759-24 Load Transient Response DS010759-27 4 Quiescent Current DS010759-19 Output Capacitor ESR DS010759-22 ...

Page 5

Typical Performance Characteristics Reset Delay DS010759-29 Typical Circuit Waveforms Applications Information EXTERNAL CAPACITORS The LM2926/7 output capacitor is required for stability. With- out it, the regulator output will oscillate at amplitudes as high as several volts peak-to-peak at frequencies up ...

Page 6

Applications Information lay capacitor. When the capacitor voltage increases 3.75V ( V ) from its discharged value, the reset output is DELAY again set HIGH. The delay time is calculated by: 6 ± The constant, 1 has ...

Page 7

Applications Information (Continued) the LM 2926/7 may fail to bring the processor under control. The LM2926/7 reset output may be more efficiently em- ployed in certain applications as a means of defeating memory WRITE lines, clocks, or external loads, rather ...

Page 8

Typical Applications (Continued) Using the Reset to De-Activate Power Loads. The LM1921 is a Fully Protected 1 Amp High-Side Driver. Using the Reset to Ensure an Accurate Display www.national.com Generating an Active High Reset Signal DS010759-12 on Power-Up or Power-Down ...

Page 9

9 ...

Page 10

... National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. 5-Lead TO-220 Outline Drawing Order Number LM2926T or LM2927T NS Package Number T05A 2 ...

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