National Semiconductor LM3914 Technical data

LM3914 Dot/Bar Display Driver

General Description

The LM3914 is a monolithic integrated circuit that senses analog voltage levels and drives 10 LEDs, providing a linear analog display. A single pin changes the display from a moving dot to a bar graph. Current drive to the LEDs is regulated and programmable, eliminating the need for resistors. This feature is one that allows operation of the whole system from less than 3V.

The circuit contains its own adjustable reference and accurate 10-step voltage divider. The low-bias-current input buffer accepts signals down to ground, or V protection against inputs of 35V above or below ground. The buffer drives 10 individual comparators referenced to the precision divider. Indication non-linearity can thus be held typically to

Versatility was designed into the LM3914 so that controller, visual alarm, and expanded scale functions are easily added on to the display system. The circuit can drive LEDs of many colors, or low-current incandescent lamps. Many LM3914s can be “chained” to form displays of 20 to over 100 segments. Both ends of the voltage divider are externally available so that 2 drivers can be made into a zero-center meter.

The LM3914 is very easy to apply as an analog meter circuit. A 1.2V full-scale meter requires only 1 resistor and a single 3V to 15V supply in addition to the 10 display LEDs. If the 1 resistor is a pot, it becomes the LED brightness control. The simplified block diagram illustrates this extremely simple external circuitry.

When in the dot mode, there is a small amount of overlap or “fade” (about 1 mV) between segments. This assures that at no time will all LEDs be “OFF”, and thus any ambiguous display is avoided. Various novel displays are possible.

⁄2%, even over a wide temperature range.

−

, yet needs no

February 2003

Much of the display flexibility derives from the fact that all outputs are individual, DC regulated currents. Various effects can be achieved by modulating these currents. The individual outputs can drive a transistor as well as a LED at the same time, so controller functions including “staging” control can be performed. The LM3914 can also act as a programmer, or sequencer.

The LM3914 is rated for operation from 0˚C to +70˚C. The LM3914N-1 is available in an 18-lead molded (N) package.

The following typical application illustrates adjusting of the reference to a desired value, and proper grounding for accurate operation, and avoiding oscillations.

Features

n Drives LEDs, LCDs or vacuum fluorescents n Bar or dot display mode externally selectable by user n Expandable to displays of 100 steps n Internal voltage reference from 1.2V to 12V n Operates with single supply of less than 3V n Inputs operate down to ground n Output current programmable from 2 mA to 30 mA n No multiplex switching or interaction between outputs n Input withstands n LED driver outputs are current regulated,

open-collectors

n Outputs can interface with TTL or CMOS logic n The internal 10-step divider is floating and can be

referenced to a wide range of voltages

35V without damage or false outputs

LM3914 Dot/Bar Display Driver

Typical Applications

LM3914

0V to 5V Bar Graph Meter

00797001

Note: Grounding method is typical of all uses. The 2.2µF tantalum or 10 µF aluminum electrolytic capacitor is needed if leads to the LED supply are 6" or longer.

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LM3914

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

Supply Voltage 25V

Voltage on Output Drivers 25V

Input Signal Overvoltage (Note 4)

Divider Voltage −100 mV to V

35V

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

Soldering Information

Dual-In-Line Package

Soldering (10 seconds) 260˚C

Plastic Chip Carrier Package

Vapor Phase (60 seconds) 215˚C

Infrared (15 seconds) 220˚C

See AN-450 “Surface Mounting Methods and Their Effect on Product Reliability” for other methods of soldering surface mount devices.

Reference Load Current 10 mA

Electrical Characteristics (Notes 2, 4)

Parameter Conditions (Note 2) Min Typ Max Units

COMPARATOR

Offset Voltage, Buffer and First Comparator

Offset Voltage, Buffer and Any Other Comparator

Gain (∆I

/∆VIN)I

LED

Input Bias Current (at Pin 5) 0V ≤ V

Input Signal Overvoltage No Change in Display −35 35 V

VOLTAGE-DIVIDER

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

Accuracy (Note 3) 0.5 2 %

VOLTAGE REFERENCE

Output Voltage 0.1 mA ≤ I

Line Regulation 3V ≤ V

Load Regulation 0.1 mA ≤ I

Output Voltage Change with Temperature

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

Output Leakage, Each Collector (Bar Mode) (Note 5) 0.1 10 µA

Output Leakage (Dot Mode) (Note 5) Pins 10– 18 0.1 10 µA

SUPPLY CURRENT

Standby Supply Current (All Outputs Off)

0V ≤ V

RLO=VRHI

=1mA

LED

0V ≤ V

RLO=VRHI

=1mA

LED

= 2 mA, I

L(REF)

≤ V+− 1.5V 25 100 nA

0˚C ≤ T

LED

LED(ON)

∆I

LED

V I

L(REF)

V I

L(REF)

=5V

LED +

≤ 18V 0.01 0.03 %/V

L(REF)

=5V

LED

≤ +70˚C, I

=5V

= 5V, I

LED

=5V I

≤ 17V I

LED

= 20 mA, V

=2mA

= 2.0 mA, I

= 5V,

= 0.2 mA

= 20V,

= 1.0 mA

≤ 12V,

= 10 mA 3 8 mA/mV

LED

≤ 4 mA,

1.2 1.28 1.34 V

≤ 4 mA,

= 1 mA,

L(REF)

= 1 mA 7 10 13 mA

L(REF)

= 2 mA 0.12 0.4

LED

=20mA 1.2 3

LED

= 2 mA 0.1 0.25

LED

=20mA 1 3

LED

= 5V,

LED

= 0.4 mA 0.15 0.4 V

L(REF)

310mV

315mV

0.4 2 %

1.5 V

Pin 1 60 150 450 µA

2.4 4.2 mA

6.1 9.2 mA

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Electrical Characteristics (Notes 2, 4) (Continued)

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is

LM3914

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:

≤ V+≤ 20 V

≤ V

−0.015V ≤ V

For higher power dissipations, pulse testing is used.

Note 3: Accuracy is measured referred to +10.000V significant error.

Note 4: Pin 5 input current must be limited to

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

output current) is disabled if pin 9 is pulled 0.9V or more below V

Note 6: The maximum junction temperature of the LM3914 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).

DCVREF,VRHI,VRLO

≤ V+0V ≤ VIN≤ V+− 1.5V

LED

RLO

RHI

≤ 12V

≤ 12 V

DCTA

= +25˚C, I

≤ (V+− 1.5V)

= 0.2 mA, V

L(REF)

at pin 6, with 0.000 VDCat pin 4. At lower full-scale voltages, buffer and comparator offset voltage may add

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

. Dot mode results when pin 9 is pulled at least 200mV below V+or left open circuit. LED No. 10 (pin 10

= 3.0V, pin 9 connected to pin 3 (Bar Mode).

LED

Definition of Terms

Accuracy: The difference between the observed threshold

voltage and the ideal threshold voltage for each comparator. Specified and tested with 10V across the internal voltage divider so that resistor ratio matching error predominates over comparator offset voltage.

Adjust Pin Current: Current flowing out of the reference adjust pin when the reference amplifier is in the linear region.

Comparator Gain: The ratio of the change in output current

) to the change in input voltage (VIN) required to pro-

LED

duce it for a comparator in the linear region. Dropout Voltage: The voltage measured at the current

source outputs required to make the output current fall by 10%.

Input Bias Current: Current flowing out of the signal input when the input buffer is in the linear region.

LED Current Regulation: The change in output current over the specified range of LED supply voltage (V

LED

)as measured at the current source outputs. As the forward voltage of an LED does not change significantly with a small change in forward current, this is equivalent to changing the voltage at the LED anodes by the same amount.

Line Regulation: The average change in reference output voltage over the specified range of supply voltage (V

Load Regulation: The change in reference output voltage

) over the specified range of load current (I

REF

L(REF)

Offset Voltage: The differential input voltage which must be applied to each comparator to bias the output in the linear region. Most significant error when the voltage across the internal voltage divider is small. Specified and tested with pin 6 voltage (V

) equal to pin 4 voltage (V

RHI

RLO

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Typical Performance Characteristics

LM3914

Supply Current vs

Temperature

Reference Voltage vs

Temperature

00797002

Operating Input Bias

Current vs Temperature

00797020

Reference Adjust Pin

Current vs Temperature

LED Current-Regulation

Dropout

00797021

00797023

00797022

LED Driver Saturation

Voltage

00797024

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Typical Performance Characteristics (Continued)

LM3914

Input Current Beyond

Signal Range (Pin 5)

LED Driver Current

Regulation

LED Current vs

Reference Loading

00797025

00797026

Total Divider Resistance

vs Temperature

00797027

Common-Mode Limits Output Characteristics

00797029

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00797028

00797030

Block Diagram (Showing Simplest Application)

LM3914

00797003

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