LM3914VSLASHNOPB中文资料德州仪器数据手册PDF规格书

1FEATURES

2• Drives LEDs, LCDs or Vacuum Fluorescents

• Bar or Dot Display Mode Externally Selectable

by User

• Expandable to Displays of 100 Steps

• Internal Voltage Reference from 1.2V to 12V

• Operates with Single Supply of Less than 3V

• Inputs Operate Down to Ground

• Output Current Programmable from 2 mA to 30

mA

• No Multiplex Switching or Interaction Between

Outputs

• Input Withstands ±35V without Damage or

False Outputs

• LED Driver Outputs are Current Regulated,

Open-collectors

• Outputs can Interface with TTL or CMOS Logic

• The Internal 10-step Divider is Floating and

can be Referenced to a Wide Range of

Voltages

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−,

yet needs no 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

½%, even over a wide temperature range.

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.

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 PDIP

(NFK) package.

The following typical application illustrates adjusting

of the reference to a desired value, and proper

grounding for accurate operation, and avoiding

oscillations.