LM3916.pdf

February 1995

LM3916 Dot/Bar Display Driver

General Description

The LM3916 is a monolithic integrated circuit that senses

analog voltage levels and drives ten LEDs, LCDs or vacuum

fluorescent displays, providing an electronic version of the

popular VU meter. One pin changes the display from a bar

graph to a moving dot display. LED current drive is regulat-

ed and programmable, eliminating the need for current limit-

ing resistors. The whole display system can operate from a

single supply as low as 3V or as high as 25V.

The IC contains an adjustable voltage reference and an ac-

curate ten-step voltage divider. The high-impedance input

buffer accepts signals down to ground and up to within 1.5V

of the positive supply. Further, it needs no protection

against inputs of g 35V. The input buffer drives 10 individual

comparators referenced to the precision divider. Accuracy is

typically better than 0.2 dB.

Audio applications include average or peak level indicators,

and power meters. Replacing conventional meters with an

LED bar graph results in a faster responding, more rugged

display with high visibility that retains the ease of interpreta-

tion of an analog display.

The LM3916 is extremely easy to apply. A 1.2V full-scale

meter requires only one resistor in addition to the ten LEDs.

One more resistor programs the full-scale anywhere from

1.2V to 12V independent of supply voltage. LED brightness

is easily controlled with a single pot.

The LM3916 is very versatile. The outputs can drive LCDs,

vacuum fluorescents and incandescent bulbs as well as

LEDs of any color. Multiple devices can be cascaded for a

dot or bar mode display for increased range and/or resolu-

tion. Useful in other applications are the linear LM3914 and

the logarithmic LM3915.

Features

Y Fast responding electonic VU meter

Y Drivers LEDs, LCDs, or vacuum fluorescents

Y Bar or dot display mode externally selectable by user

Y Expandable to displays of 70 dB

Y Internal voltage reference from 1.2V to 12V

Y Operates with single supply of 3V to 25V

Y Inputs operate down to ground

Y Output current programmable from 1 mA to 30 mA

Y Input withstands g 35V without damage or false outputs

Y Outputs are current regulated, open collectors

Y Directly drives TTL or CMOS

Y The internal 10-step divider is floating and can be refer-

enced to a wide range of voltages

The LM3916 is rated for operation from 0 § Cto a 70 § C. The

LM3916N is available in an 18-lead molded DIP package.

Typical Applications

0V TO 10V VU Meter

V REF e 1.25V

1 a

a R2 c 80 m A

Note 1: Capacitor C1 is required if

leads to the LED supply are 6 × or

longer.

Note 2: Circuit as shown is wired for

dot mode. For bar mode, connect pin

9 to pin 3. V LED must be kept below

7V or dropping resistor should be

used to limit IC power dissipation.

12.5V

R1 a

V REF

2.2 k X

I LED e

TL/H/7971±1

C 1995 National Semiconductor Corporation

TL/H/7971

RRD-B30M115/Printed in U. S. A.

Absolute Maximum Ratings

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales

Office/Distributors for availability and specifications.

Power Dissipation (Note 5)

Molded DIP (N)

1365 mW

Input Signal Overvoltage (Note 3) g 35V

Divider Voltage b 100 mV to V a

Reference Load Current 10 mA

Storage Temperature Range b 55 § Cto a 150 § C

Lead Temperature (Soldering, 10 seconds)

260 § C

Supply Voltage

25V

Voltage on Output Drivers

25V

Electrical Characteristics (Notes 1 and 3)

Parameter

Conditions (Note 1)

Min Typ Max Units

COMPARATORS

Offset Voltage, Buffer and First

0V s V RLO e V RHI s 12V,

10 mV

Comparator I LED e 1mA

Offset Voltage, Buffer and Any Other Comparator 0V s V RLO e V RHI s 12V, I LED e 1 mA

15 mV

Gain ( D I LED / D V IN )

I (REF) e 2 mA, I LED e 10 mA

mA/mV

Input Bias Current (at Pin 5)

0V s V IN s (V a b 1.5V)

25 100

Input Signal Overvoltage

No Change in Display

b 35

VOLTAGE DIVIDER

Divider Resistance

Total, Pin 6 to 4

12 17

k X

Relative Accuracy (Input Change

(Note 2)

Between Any Two Threshold Points)

b 1dB s V IN s 3 dB

0.75 1.0 1.25

b 7dB s V IN s b 1 dB

1.5 2.0 2.5

b 10 dB s V IN s b 7 dB

2.5 3.0 2.5

Absolute Accuracy

(Note 2)

V IN e 2, 1, 0, b 1dB

b 0.25

a 0.25 dB

V IN eb 3, b 5dB

b 0.5

a 0.5

V IN eb 7, b 10, b 20 dB

b 1

a 1

VOLTAGE REFERENCE

Output Voltage

0.1 mA s I L(REF) s 4mA,

1.2 1.28 1.34

V a e V LED e 5V

Line Regulation

3V s V a s 18V

0.01 0.03 %/V

Load Regulation

0.1 mA s I L(REF) s 4mA,

0.4

2 %

V a e V LED e 5V

Output Voltage Change with Temperature

0 § C s T A s a 70 § C,I L(REF) e 1 mA,

V a e V LED e 5V

Adjust Pin Current

75 120 m A

OUTPUT DRIVERS

LED Current

V a e V LED e 5V, I L(REF) e 1 mA

10 13 mA

LED Current Difference (Between Largest

V LED e 5V, I LED e 2 mA

0.12 0.4 mA

and Smallest LED Currents)

V LED e 5V, I LED e 20 mA

1.2

3 mA

LED Current Regulation

2V s V LED s 17V

I LED e 2 mA

0.1 0.25 mA

I LED e 20 mA

3 mA

Dropout Voltage

I LED(ON) e 20 mA @ V LED e 5V,

1.5

D I LED e 2mA

Saturation Voltage

I LED e 2.0 mA, I L(REF) e 0.4 mA

0.15 0.4

Output Leakage, Each Collector

Bar Mode (Note 4)

0.1 100 m A

Output Leakage

Dot Mode (Note 4)

Pins 10±18

0.1 100 m A

Pin 1

60 150 450 m A

Electrical Characteristics (Note 1) (Continued)

Parameter

Conditions (Note 1)

Min

Typ

Max

Units

SUPPLY CURRENT

Standby Supply Current

V a ea 5V, I L(REF) e 0.2 mA

2.4

4.2

(All Outputs Off)

V a ea 20V, I L(REF) e 1.0 mA

6.1

9.2

Note 1: Unless otherwise stated, all specifications apply with the following conditions:

3V DC s V a s 20 V DC b 0.015V s V RLO s 12 V DC T A e 25 § C, I L(REF) e 0.2 mA, pin 9 connected to pin 3 (bar mode).

3V DC s V LED s V a V REF ,V RHI ,V RLO s (V a b 1.5V) For higher power dissipations, pulse testing is used.

b 0.015V s V RHI s 12 V DC 0V s V IN s V a b 1.5V

Note 2: Accuracy is measured referred to a 3dB ea 10.000 VDC at pin 5, with a 10.000 VDC at pin 6, and 0.000 VDC at pin 4. At lower full-scale voltages, buffer

and comparator offset voltage may add significant error. See table for threshold voltages.

Note 3: Pin 5 input current must be limited to g 3 mA. The addition of a 39k resistor in series with pin 5 allows g 100V signals without damage.

Note 4: Bar mode results when pin 9 is within 20 mV of V a . Dot mode results when pin 9 is pulled at least 200 mV below V a . LED Ý10 (pin 10 output current) is

disabled if pin 9 is pulled 0.9V or more below V LED .

Note 5: The maximum junction temperature of the LM3916 is 100 § C. Devices must be derated for operation at elevated temperatures. Junction to ambient thermal

resistance is 55 § C/W for the molded DIP (N package).

LM3916 Threshold Voltage (Note 2)

Volts

Min Typ Max

9.985 10.000 10.015 b 3 g (/2

4.732 5.012 5.309

2 g (/4

8.660 8.913 9.173 b 5 g (/2

3.548 3.981 4.467

1 g (/4

7.718 7.943 8.175 b 7 g 1 2.818 3.162 3.548

0 g (/4

6.879 7.079 7.286 b 10 g 1 1.995 2.239 2.512

b 1 g (/2

5.957 6.310 6.683 b 20 g 1 0.631 0.708 0.794

Typical Performance Characteristics

Supply Current vs

Operating Input Bias

Reference Voltage vs

Temperature

Current vs Temperature

Temperature

Reference Adjust Pin

LED Current-Regulation

LED Driver Saturation

Current vs Temperature

Dropout

Voltage

Input Current Beyond

LED Current vs

LED Driver Current

Signal Range (Pin 5)

Referenced Loading

Regulation

TL/H/7971±2

Total Divider Resistance

vs Temperature

Common-Mode Limits

Output Characteristics

TL/H/7971±3

Block Diagram (Showing Simplest Application)

TL/H/7971±4

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