NSC LM391N-100 Datasheet

LM391 Audio Power Driver

General Description

The LM391 audio power driver is designed to drive external
power transistors in 10 to 100 watt power amplifier designs.
High power supply voltage operation and true high fidelity
performance distinguish this IC. The LM391 is internally pro­tected for output faults and thermal overloads; circuitry pro­viding output transistor protection is user programmable.

Equivalent Schematic and Connection Diagram

Features

Y

High Supply Voltage

Y

Low Distortion 0.01%

Y

Low Input Noise 3 mV

Y

High Supply Rejection 90 dB

Y

Gain and Bandwidth Selectable

Y

Dual Slope SOA Protection

Y

Shutdown Pin

December 1994

g

50V max

LM391 Audio Power Driver

Dual-In-Line Package

TL/H/7146– 1

Top View

TL/H/7146– 2

Order Number LM391N-100

See NS Package Number N16A

C

1995 National Semiconductor Corporation RRD-B30M115/Printed in U. S. A.

TL/H/7146

Absolute Maximum Ratings

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.

Supply Voltage

LM391N-100

g

50V ora100V

Input Voltage Supply Voltage less 5V

Shutdown Current (Pin 14) 1 mA

Electrical Characteristics T

e

25§C (The following are for V

A

Parameter Conditions Min Typ Max Units

Quiescent Current Current in Pin 15

LM391N-100 V

e

056

IN

Output Swing Positive V

Negative V

Drive Current Source (Pin 8) 5 mA

Sink (Pin 5) 5 mA

Noise (20 Hz–20 kHz) Input Referred 3 mV

Supply Rejection Input Referred 70 90 dB

Total Harmonic Distortion fe1 kHz 0.01 %

e

f

20 kHz 0.10 0.25 %

Intermodulation Distortion 60 Hz, 7 kHz, 4:1 0.01 %

Open Loop Gain fe1 kHz 1000 5500 V/V

Input Bias Current 0.1 1.0 mA

Input Offset Voltage 5 20 mV

Positive Current Limit V

Negative Current Limit V

BE

BE

Pin 10–9 650 mV

Pin 9–13 650 mV

Positive Current Limit Bias Current Pin 10 10 100 mA

Negative Current Limit Bias Current Pin 13 10 100 mA

Pin 14 Current Comments

Minimum pin 14 current required for shutdown is 0.5 mA, and must not exceed 1 mA.
Maximum pin 14 current for amplifier not shut down is 0.05 mA.
The typical shutdown switch point current is 0.2 mA.

Note 1: For operation in ambient temperatures above 25§C, the device must be derated based on a 150§C maximum junction temperature and a thermal resistance

C/W junction to ambient.

of 90

§

Package Dissipation (Note 1) 1.39W

Storage Temperature

b

65§Ctoa150§C

Operating Temperature 0§Ctoa70§C

Lead Temp. (Soldering, 10 sec.) 260§C

Thermal Resistance

i

JC

i

JA

a

e

90% V

a

MAX

and V

b

e

90% V

b

20§C/W
63§C/W

MAX

.)

mA

a

b

7V

b

a

7V

a

b

5V

b

a

5V

Typical Applications

FIGURE 1. LM391 with External ComponentsÐProtection Circuitry Not Shown

TL/H/7146– 3

2

Typical Performance Characteristics

Output Power vs Supply Voltage Frequency (R

Total Harmonic Distortion vs

e

8X)

L

Input Referred Power Supply

Open Loop Gain vs Frequency Rejection vs Frequency

Total Harmonic Distortion vs
Frequency (R

e

4X)

L

Total Harmonic Distortion vs
AB Bias Current

TL/H/7146– 4

Pin Descriptions

Pin No. Pin Name Comments

1
2
3 Compensation Sets the dominant pole
4 Ripple Filter Improves negative supply rejection
5 Sink Output Drives output devices and is emitter of AB bias V
6 BIAS Base of V
7 BIAS Collector of V
8 Source Output Drives output devices

9 Output Sense Biases the IC and is used in protection circuits
10
11
12
13
14 Shutdown Shuts off amplifier when current is pulled out of pin
15 V
16 V

a

Input Audio input

b

Input Feedback input

multiplier

BE

multiplier

BE

a

Current Limit Base of positive side protection circuit transistor

a

SOA Diode Diode used for dual slope SOA protection

b

SOA Diode Diode used for dual slope SOA protection

b

Current Limit Base of negative side protection circuit transistor

a

b

Positive supply
Negative supply

3

multiplier

BE

External Components (Figure 1)

Component Typical Value Comments

C

IN

R

IN

R

f

2

R

f

1

C

f

C

C

R

A

R

B

C

AB

C

R

R

eb

R

O

C

O

R

E

R

TH

C2,C

X

L

Ê

2

1 mF Input coupling capacitor sets a low frequency pole with RIN.

1

e

f

L

2qRINC

IN

100k Sets input impedance and DC bias to input.

100k Feedback resistor; for minimum offset voltage at the output this should be equal to RIN.

5.1k Feedback resistor that works with R

R

f

A

e1a

V

2

R

f

1

to set the voltage gain.

f

2

10 mF Feedback capacitor. This reduces the gain to unity at DC for minimum offset voltage at the

output. Also sets a low frequency pole with R

1

e

f

L

2qR

C

f

f

1

.

f

1

5 pF Compensation capacitor. Sets gain bandwidth product and a high frequency pole.

1

e

GBW

2q5000C

Max fhfor stable design&500 kHz.

GBW

e

,f

h

A

C

V

3.9k AB bias resistor.

10k AB bias potentiometer. Adjust to set bias current in the output stage.

0.1 mF Bypass capacitor for bias. This improves high frequency distortion and transient response.

5 pF Ripple capacitor. This improves negative supply rejection at midband and high frequencies.

C

, if used, must equal CC.

R

100X Bleed resistor. This removes stored charge in output transistors.

2.7X Output compensation resistor. This resistor and COcompensate the output stage. This value

will vary slightly for different output devices.

0.1 mF Output compensation capacitor. This works with ROto form a zero that cancels fbof the

output power transistors.

0.3X Emitter degeneration resistor. This resistor gives thermal stability to the output stage

quiescent current. IRC PW5 type.

39k Shutdown resistor. Sets the amount of current pulled out of pin 14 during shutdown.

1000 pF Compensation capacitors for protection circuitry.

10Xll5 m H Used to isolate capacitive loads, usually 20 turns of wire wrapped around a 10X, 2W resistor.

4