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8178
PRODUCT PREVIEW
(Subject to change without notice)
April 5, 1996
3
VR
12
7.7 V
VR
LOW-DROPOUT,
7.7 V PREREGULATOR
Designed specifically to meet the stringent requirements of automo-
tive applications, the A8178LLR and A8178LLT provide an output
voltage of 7.7 V ±15% for supply voltages greater than 6.9 V. They
also provide a low-dropout tracking output for supply voltages down to
2.5 V. These regulators are intended to be used with sensitive automo-
tive electronics systems that do not have the capability of low dropout
operation and cannot withstand the high-voltage transients typical of
automotive applications. These 7.7 V preregulators will withstand all
ISO pulses (ignition coil disconnect requires an external diode) and will
continue to operate during positive power supply transients (noise).
These devices are supplied in small-outline plastic transistor
packages for surface-mount applications. The A8178LLR is supplied in
the minimum footprint SOT-23/TO-236AB; the A8178LLT is furnished in
the SOT-89/TO-243AA for increased allowable package power dissipa-
tion.
12
3
Dwg. PD-0xx
ABSOLUTE MAXIMUM RATINGS
Input Voltage, VI . . . . . . . . . . . . . . 30 V
Reverse Input Voltage, VRI . . . . -120 V
Output Current, IO . . . . . . . . . . . . TBD*
Operating Temperature Range,
TA . . . . . . . . . . . . -40°C to +150°C
Junction Temperature, TJ . . . . +150°C
Storage Temperature Range,
TS . . . . . . . . . . . . -40°C to +170°C
* Output current rating is limited by input voltage,
duty cycle, and ambient temperature. Under
any set of conditions, do not exceed a junction
temperature of +150°C. See next page.
This document contains information on a product under development. Allegro
MicroSystems, Inc. reserves the right to change or discontinue this product without
notice.
Always order by complete part number: A8178LLT .

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8178
LOW-DROPOUT,
7.7 V PREREGULATOR
ELECTRICAL CHARACTERISTICS over operating temperature range.
Characteristic
Symbol Test Conditions
Output Voltage
Output Volt. Temp. Coeff.
Line Regulation
Load Regulation
Quiescent Current
Power Dissipation
Thermal Resistance*
VO
αVO
VO(VI)
VO(IO)
IQ
Pd
RθJA
6.9 V VI 24 V
2.5 V VI 6.9 V
VI = 120 V, pulse test
VI = 13.5 V, IO = 0
2.5 V VI 8 V, IO = 0
VI = 13.5 V, IO = 15 mA
A8178LLR
A8178LLT
Typical values are at TA = +25°C and are given for circuit design information only.
*Mounted on 2.24" x 2.24" solder-coated copper-clad board in still air.
Min.
6.5
VI - 0.4
Limits
Typ.
Max.
7.7 8.8
——
— 11
— TBD
— TBD
— TBD
— 2.5
— 5.6
— 130
575 —
200 —
Units
V
V
V
mV/°C
mV
mV
mA
mA
mW
°C/W
°C/W
ISO
Pulse No.
1
2
3a
3b
4
5
6
7
INTERNAL PROTECTIVE FEATURES
Test
Inductive Turn Off (Negative)
Inductive Turn Off (Positive)
Capacitive/Inductive Coupling (Neg)
Capacitive/Inductive Coupling (Pos)
Reverse Battery
Load Dump
Ignition Coil Disconnect
EXTERNAL PROTECTION REQ’D
Field Decay (Negative)
Test Conditions (at TA = +25°C)
VS = -100 V, RS = 10 , tr = 1 µs, td = 2 ms
VS = 100 V, RS = 10 , tr = 1 µs, td = 50 µs, non-operating
VS = -150 V, RS = 50 , tr = 50 ns, td = 100 ns
VS = 100 V, RS = 50 , tr = 50 ns, td = 100 ns
VS = -14 V, td = 20 s, non-operating
VS = 86.5 V, RS = 0.5 , tr = 5 ms, td = 400 ms
VS = -300 V, RS = 30 , tr = 60 µs, td = 300 µs
VS = -80 V, RS = 10 , tr = 5 ms, td = 100 ms
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 1996 Allegro MicroSystems, Inc.

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8178
LOW-DROPOUT,
7.7 V PREREGULATOR
A8178LLR
Dimensions in Inches
(for reference only)
0.120
0.110
0.020
0.015
0.055
3
0.047 1
2
0.044
0.035
0.1039
0.083
0.027
REF
0.024
0.018
0.004
0.0005
0.080
0.070
0.040
0.035
0.007
0.003
Dwg. MA-010 in
Dimensions in Millimeters
(controlling dimensions)
3.04
2.80
0.51
0.37
1.40
3
2.64
1.20 1
2 2.10
0.60
0.45
0.10
0.013
1.03
2.05 0.89
1.78
1.12
0.89
0.69
REF
0.18
0.085
Dwg. MA-010 mm
NOTES: 1. Lead spacing tolerance is non-cumulative.
2. Exact body and lead configuration at vendor’s option within limits shown.

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8178
LOW-DROPOUT,
7.7 V PREREGULATOR
0.155
0.167
A8178LLT
Dimensions in Inches
(for reference only)
0.173
0.181
0.064
0.072
0.055
0.063
0.090
1 2 3 0.102
0.084
0.090
0.014
0.017
0.035
0.047
0.059
BSC
0.014
0.019
0.017
0.022
0.118
BSC
Dwg. MA-009-3 in
3.94
4.25
Dimensions in Millimeters
(controlling dimensions)
4.40
4.60
1.62
1.83
1.40
1.60
2.29
1 2 3 2.60
2.13
2.29
0.35
0.44
0.89
1.20
1.50
BSC
0.36
0.48
0.44
0.56
3.00
BSC
Dwg. MA-009-3 mm
NOTES: 1. Lead spacing tolerance is non-cumulative.
2. Exact body and lead configuration at vendor’s
option within limits shown.
Allegro MicroSystems, Inc. reserves the right to make, from time to time, such
departures from the detail specifications as may be required to permit improvements
in the design of its products.
The information included herein is believed to be accurate and reliable.
However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for
any infringements of patents or other rights of third parties which may result from its
use.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000