A8178 - Allegro MicroSystems, Inc.

Data Sheet

27468.23

LOW-DROPOUT,

7.7 V PREREGULATOR

Designed specifically to meet the stringent requirements of automo-

tive applications, the A8178LLT provides an output voltage of 7.7 V

±15% for supply voltages greater than 6.9 V. This device also provide

a low-dropout tracking output for supply voltages down to 2.5 V. This

regulator is intended to be used with sensitive automotive electronics

systems that do not have the capability of low dropout operation and

cannot withstand the high-voltage transients typical of automotive

applications. This 7.7 V preregulator will withstand all ISO pulses

(ignition coil disconnect requires an external diode) and will continue to

operate during positive power supply transients (noise).

This device is supplied in a small-outline plastic transistor package

for surface-mount applications. The A8178LLT is furnished in the SOT-

89/TO-243AA for increased allowable package power dissipation.

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 .

8178

PRODUCT PREVIEW

(Subject to change without notice)

October 9, 2001

Dwg. PD-0xx

VR 7.7 V

2 31

8178

LOW-DROPOUT,

7.7 V PREREGULATOR

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

ELECTRICAL CHARACTERISTICS over operating temperature range.

Limits

Characteristic Symbol Test Conditions Min. Typ. Max. Units

Output Voltage VO6.9 V ≤ VI ≤ 24 V 6.5 7.7 8.8 V

2.5 V ≤ VI ≤ 6.9 V VI - 0.4 — — V

VI = 120 V, pulse test — — 11 V

Output Volt. Temp. Coeff. αVO — — TBD mV/°C

Line Regulation ∆VO(∆VI) — — TBD mV

Load Regulation ∆VO(∆IO) — — TBD mV

Quiescent Current IQVI = 13.5 V, IO = 0 — — 2.5 mA

2.5 V ≤ VI ≤ 8 V, IO = 0 — — 5.6 mA

Power Dissipation PdVI = 13.5 V, IO = 15 mA — — 130 mW

Thermal Resistance* RθJA — 200 — °C/W

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.

INTERNAL PROTECTIVE FEATURES

ISO

Pulse No. Test Test Conditions (at TA = +25°C)

1 Inductive Turn Off (Negative) VS = -100 V, RS = 10 Ω, tr = 1 µs, td = 2 ms

2 Inductive Turn Off (Positive) VS = 100 V, RS = 10 Ω, tr = 1 µs, td = 50 µs, non-operating

3a Capacitive/Inductive Coupling (Neg) VS = -150 V, RS = 50 Ω, tr = 50 ns, td = 100 ns

3b Capacitive/Inductive Coupling (Pos) VS = 100 V, RS = 50 Ω, tr = 50 ns, td = 100 ns

4 Reverse Battery VS = -14 V, td = 20 s, non-operating

5 Load Dump VS = 86.5 V, RS = 0.5 Ω, tr = 5 ms, td = 400 ms

6 Ignition Coil Disconnect VS = -300 V, RS = 30 Ω, tr = 60 µs, td = 300 µs

EXTERNAL PROTECTION REQ’D

7 Field Decay (Negative) VS = -80 V, RS = 10 Ω, tr = 5 ms, td = 100 ms

Dwg. MA-009-3 in

123

0.064

0.072

0.155

0.167

0.059

BSC

0.014

0.019

0.035

0.047

0.090

0.102

0.055

0.063 0.014

0.017

0.084

0.090

0.017

0.022

0.118

BSC

0.173

0.181

Dimensions in Millimeters

(controlling dimensions)

Dwg. MA-009-3 mm

123

4.40

4.60

1.62

1.83

3.94

4.25

1.50

BSC

0.36

0.48

0.89

1.20

2.29

2.60

1.40

1.60 0.35

0.44

2.13

2.29

0.44

0.56

3.00

BSC

A8178LLT

Dimensions in Inches

(for reference only)

NOTES: 1.Lead spacing tolerance is non-cumulative.

2.Exact body and lead configuration at vendor’s

option within limits shown.

8178

LOW-DROPOUT,

7.7 V PREREGULATOR

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

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.