National Semiconductor LM3916 Technical data

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 regulated
and programmable, eliminating the need for current limiting
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
accurate 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
parators 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 interpreta­tion 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.

±

35V. The input buffer drives 10 individual com-

January 2000

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 resolu­tion. Useful in other applications are the linear LM3914 and
the logarithmic LM3915.

Features

n Fast responding electronic VU meter
n Drivers LEDs, LCDs, or vacuum fluorescents
n Bar or dot display mode externally selectable by user
n Expandable to displays of 70 dB
n Internal voltage reference from 1.2V to 12V
n Operates with single supply of 3V to 25V
n Inputs operate down to ground
n Output current programmable from 1 mA to 30 mA
n Input withstands
n Outputs are current regulated, open collectors
n Directly drives TTL or CMOS
n The internal 10-step divider is floating and can be

referenced to a wide range of voltages

The LM3916 is rated for operation from 0˚C to +70˚C. The
LM3916N-1 is available in an 18-lead molded DIP package.

±

35V without damage or false outputs

LM3916 Dot/Bar Display Driver

© 2004 National Semiconductor Corporation DS007971 www.national.com

Typical Applications

LM3916

0V to 10V VU Meter

00797101

Notes: Capacitor C1 is required if leads to the LED supply are 6" or longer.

Circuit as shown is wired for dot mode. For bar mode, connect pin 9 to pin 3. V
dissipation.

must be kept below 7V or dropping resistor should be used to limit IC power

LED

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LM3916

Absolute Maximum Ratings (Note 1)

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

Power Dissipation (Note 6)

Molded DIP (N) 1365 mW

Input Signal Overvoltage (Note 4)

Divider Voltage −100 mV to V

Reference Load Current 10 mA

Storage Temperature Range −55˚C to +150˚C

Lead Temperature

(Soldering, 10 seconds) 260˚C

±

35V

Supply Voltage 25V

Voltage on Output Drivers 25V

Electrical Characteristics (Notes 2, 4)

Parameter Conditions (Note 2) Min Typ Max Units

COMPARATORS

Offset Voltage, Buffer and First Comparator 0V ≤ V

Offset Voltage, Buffer and Any Other Comparator 0V ≤ V

Gain (∆I

/ ∆VIN)I

LED

Input Bias Current (at Pin 5) 0V ≤ V

I

LED

I

LED

(REF)

RLO=VRHI

=1mA

RLO=VRHI

=1mA

= 2 mA, I

≤ (V+−1.5V) 25 100 nA

IN

Input Signal Overvoltage No Change in Display −35 35 V

VOLTAGE DIVIDER

Divider Resistance Total, Pin 6 to 4 8 12 17 kΩ

Relative Accuracy (Input Change
Between Any Two Threshold Points)

(Note 3)

−1 dB ≤ V

−7 dB ≤ V

IN

IN

−10 dB ≤ V

Absolute Accuracy (Note 3)

=2,1,0,−1dB

V

IN

= −3, −5 dB

V

IN

= −7, −10, −20 dB

V

IN

VOLTAGE REFERENCE

Output Voltage 0.1 mA ≤ I

+

V

Line Regulation 3V ≤ V

Load Regulation 0.1 mA ≤ I

+

V

Output Voltage Change with Temperature 0˚C ≤ T

+

V

L(REF)

=V

LED
+

≤ 18V 0.01 0.03 %/V

L(REF)

=V

LED

≤ +70˚C, I

A

=V

LED

Adjust Pin Current 75 120 µA

OUTPUT DRIVERS

LED Current V

LED Current Difference (Between Largest and
Smallest LED Currents)

LED Current Regulation 2V ≤ V

Dropout Voltage I

Saturation Voltage I

+

V

LED

V

LED

I

LED

I

LED

LED(ON)

∆I

LED

LED

=V

LED

= 5V, I
= 5V, I

LED

2mA
=20mA

=20mA@V

=2mA

= 2.0 mA, I

Output Leakage, Each Collector Bar Mode (Note 5) 0.1 100 µA

Output Leakage Dot Mode (Note 5)

Pins 10– 18 0.1 100 µA

Pin 1 60 150 450 µA

SUPPLY CURRENT

LED

≤ 3dB
≤ −1 dB

≤ −7 dB

IN

= 5Vg

=5V

=5V

= 5V, I

LED

LED

≤ 17V

≤ 12V,

≤ 12V,

310 mV

315 mV

= 10 mA 3 8 mA/mV

0.75

1.5

2.5

−0.25

−0.5

−1

≤ 4 mA,

1.2 1.28 1.34 V

≤ 4 mA,

= 1 mA,

L(REF)

= 1 mA 7 10 13 mA

L(REF)

=2mA
=20mA

1.0

1.25

2.0

3.0

2.5

2.5

+0.25

+0.5

+1

0.4 2 %

1%

0.12

1.2

0.4
3

0.110.25
3

= 5V,

LED

= 0.4 mA 0.15 0.4 V

L(REF)

1.5 V

dB
dB
dB

dB
dB
dB

mA
mA

mA
mA

+

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Electrical Characteristics (Notes 2, 4) (Continued)

LM3916

Parameter Conditions (Note 2) Min Typ Max Units

Standby Supply Current
(All Outputs Off)

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating ratings indicate conditions for which the device is
functional, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which
guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit
is given, however, the typical value is a good indication of device performance.

Note 2: Unless otherwise stated, all specifications apply with the following conditions:

3V

≤ V+≤ 20 V

DC

≤ V

3V

DC

−0.015V ≤ V

Note 3: Accuracy is measured referred to +3 dB = +10.000 V
comparator offset voltage may add significant error. See table for threshold voltages.

Note 4: Pin 5 input current must be limited to

Note 5: Bar mode results when pin 9 is within 20 mV of V

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

Note 6: 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).

LED

RHI

≤ V

≤ 12 V

DC

+

−0.015V ≤ V

V

REF,VRHI,VRLO

0V ≤ VIN≤ V+− 1.5V

DC

≤ 12 V

RLO

DC

≤ (V+− 1.5V) For higher power dissipations, pulse testing is used.

±

3 mA. The addition of a 39k resistor in series with pin 5 allows±100V signals without damage.

.

LED

+

V

= + 5V, I

+

= + 20V, I

V

TA= 25˚C, I

at pin 5, with +10.000 VDCat pin 6, and 0.000 VDCat pin 4. At lower full-scale voltages, buffer and

DC

+

. Dot mode results when pin 9 is pulled at least 200 mV below V+. LED #10 (pin 10 output current) is

L(REF)

= 0.2 mA

L(REF)

= 1.0 mA

L(REF)

= 0.2 mA, pin 9 connected to pin 3 (bar mode).

2.4

6.1

4.2

9.2

LM3916 Threshold Voltage (Note 3)

dB

Min Typ Max Min Typ Max

3 9.985 10.000 10.015 −3

1

±

2

⁄48.660 8.913 9.173 −5

1

±

1

⁄47.718 7.943 8.175 −7±1 2.818 3.162 3.548

1

±

0

⁄46.879 7.079 7.286 −10±1 1.995 2.239 2.512

1

±

−1

⁄25.957 6.310 6.683 −20±1 0.631 0.708 0.794

Volts

dB

1

±

⁄24.732 5.012 5.309

1

±

⁄23.548 3.981 4.467

Volts

mA
mA

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Typical Performance Characteristics

LM3916

Supply Current vs

Temperature

Reference Voltage vs

Temperature

00797135

Operating Input Bias

Current vs Temperature

00797136

Reference Adjust Pin

Current vs Temperature

LED Current-Regulation

Dropout

00797137

00797139

00797138

LED Driver Saturation

Voltage

00797140

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Typical Performance Characteristics (Continued)

LM3916

Input Current Beyond

Signal Range (Pin 5)

LED Driver Current

Regulation

LED Current vs

Referenced Loading

00797141

00797142

Total Divider Resistance

vs Temperature

00797143

Common-Mode Limits Output Characteristics

00797145

00797144

00797146

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Block Diagram (Showing Simplest Application)

LM3916

00797104

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Functional Description

The simplified LM3916 block diagram is included to give the

LM3916

general idea of the circuit’s operation. A high input imped­ance buffer operates with signals from ground to 12V, and is
protected against reverse and overvoltage signals. The sig­nal is then applied to a series of 10 comparators; each of
which is biased to a different comparison level by the resistor
string.

In the example illustrated, the resistor string is connected to
the internal 1.25V reference voltage. As the input voltage
varies from 0 to 1.25, the comparator outputs are driven low
one by one, switching on the LED indicators. The resistor
divider can be connected between any 2 voltages, providing
that they are at least 1.5V below V

INTERNAL VOLTAGE REFERENCE

The reference is designed to be adjustable and develops a
nominal 1.25V between the REF OUT (pin 7) and REF ADJ
(pin 8) terminals. The reference voltage is impressed across
program resistor R1 and, since the voltage is constant, a
constant current I

then flows through the output set resistor

1

R2 giving an output voltage of:

+

and no lower than V−.

lighted LED, and this current will be relatively constant de­spite supply voltage and temperature changes. Current
drawn by the internal 10-resistor divider, as well as by the
external current and voltage-setting divider should be in­cluded in calculating LED drive current. The ability to modu­late LED brightness with time, or in proportion to input volt­age and other signals can lead to a number of novel displays
or ways of indicating input overvoltages, alarms, etc.

The LM3916 outputs are current-limited NPN transistors as
shown below. An internal feedback loop regulates the tran­sistor drive. Output current is held at about 10 times the
reference load current, independent of output voltage and
processing variables, as long as the transistor is not satu­rated.

LM3916 Output Circuit

00797106

00797105

Since the 120 µA current (max) from the adjust terminal
represents an error term, the reference was designed to
minimize changes of this current with V

+

and load changes.
For correct operation, reference load current should be be­tween 80 µA and 5 mA. Load capacitance should be less
than 0.05 µF.

CURRENT PROGRAMMING

A feature not completely illustrated by the block diagram is
the LED brightness control. The current drawn out of the
reference voltage pin (pin 7) determines LED current. Ap­proximately 10 times this current will be drawn through each

Outputs may be run in saturation with no adverse effects,
making it possible to directly drive logic. The effective satu­ration resistance of the output transistors, equal to R

plus

E

the transistors’ collector resistance, is about 50Ω. It’s also
possible to drive LEDs from rectified AC with no filtering. To
avoid oscillations, the LED supply should be bypassed with a

2.2 µF tantalum or 10 µF aluminum electrolytic capacitor.

MODE PIN USE

Pin 9, the Mode Select input, permits chaining of multiple
devices, and controls bar or dot mode operation. The follow­ing tabulation shows the basic ways of using this input. Other
more complex uses will be illustrated in the applications.

Bar Graph Display: Wire Mode Select (pin 9) directly to pin

+

pin).

3(V
Dot Display, Single LM3916 Driver: Leave the Mode Select

pin open circuit.
Dot Display, 20 or More LEDs: Connect pin 9 of the first

drivers in the series (i.e., the one with the lowest input
voltage comparison points) to pin 1 of the next higher
LM3916 driver. Continue connecting pin 9 of lower input
drivers to pin 1 of higher input drivers for 30 or more LED
displays. The last LM3916 driver in the chain will have pin 9
left open. All previous drivers should have a 20k resistor in
parallel with LED #9 (pin 11 to V

LED

).

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Mode Pin Functional Description

This pin actually performs two functions. Refer to the simpli­fied block diagram below.

Block Diagram of Mode Pin Function

*High for bar

DOT OR BAR MODE SELECTION

The voltage at pin 9 is sensed by comparator C1, nominally
referenced to (V

+

−100 mV). The chip is in bar mode when
pin 9 is above this level; otherwise it’s in dot mode. The
comparator is designed so that pin 9 can be left open circuit
for dot mode.

Taking into account comparator gain and variation in the
100 mV reference level, pin 9 should be no more than 20 mV
below V
open circuit) for dot mode. In most applications, pin 9 is
either open (dot mode) or tied to V

+

for bar mode and more than 200 mV below V+(or

+

(bar mode). In bar mode,
pin 9 should be connected directly to pin 3. Large currents
drawn from the power supply (LED current, for example)
should not share this path so that large IR drops are avoided.

00797107

DOT MODE CARRY

In order for display to make sense when multiple drivers are
cascaded in dot mode, special circuitry has been included to
shut off LED #10 of the first device when LED #1 of the
second device comes on. The connection for cascading in
dot mode has already been described and is depicted in
Figure 1.

As long as the input signal voltage is below the threshold of
the second driver, LED #11 is off. Pin 9 of driver #1 thus sees
effectively an open circuit so the chip is in dot mode. As soon
as the input voltage reaches the threshold of LED #11, pin 9
of driver #1 is pulled an LED drop (1.5V or more) below

. This condition is sensed by comparator C2, refer-

V

LED

enced 600 mV below V

. This forces the output of C2 low,

LED

which shuts off output transistor Q2, extinguishing LED #10.

is sensed via the 20k resistor connected to pin 11. The

V

LED

very small current (less than 100 µA) that is diverted from
LED #9 does not noticeably affect its intensity.

An auxiliary current source at pin 1 keeps at least 100 µA
flowing through LED #11 even if the input voltage rises high
enough to extinguish the LED. This ensures that pin 9 of
driver #1 is held low enough to force LED #10 off when any
higher LED is illuminated. While 100 µA does not normally
produce significant LED illumination, it may be noticeable
when using high-efficiency LEDs in a dark environment. If
this is bothersome, the simple cure is to shunt LED #11 (and
LED #1) with a 10k resistor. The 1V 1R drop is more than the
900 mV worst case required to hold off LED #10 yet small
enough that LED #11 does not conduct significantly.

In some circuits a number of outputs on the higher device
are not used. Examples include the high resolution VU meter
and the expanded range VU meter circuits (see Typical
Applications). To provide the proper carry sense voltage in
dot mode, the LEDs of the higher driver IC are tied to V

LED

through two series-connected diodes as shown in Figure 2.
Shunting the diodes with a 1k resistor provides a path for
driver leakage current.

LM3916

FIGURE 1. Cascading LM3914/15/16 Series in Dot Mode

00797108

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