Datasheet

LM3914

www.ti.com

SNVS761B –JANUARY 2000–REVISED MARCH 2013

OTHER DEVICE CHARACTERISTICS

The LM3914 is relatively low-powered itself, and since any number of LEDs can be powered from about 3V, it is

a very efficient display driver. Typical standby supply current (all LEDs OFF) is 1.6mA (2.5mA max). However,

any reference loading adds 4 times that current drain to the V

(pin 3) supply input. For example, an LM3914

with a 1mA reference pin load (1.3k), would supply almost 10mA to every LED while drawing only 10mA from its

pin supply. At full-scale, the IC is typically drawing less than 10% of the current supplied to the display.

The display driver does not have built-in hysteresis so that the display does not jump instantly from one LED to

the next. Under rapidly changing signal conditions, this cuts down high frequency noise and often an annoying

flicker. An “overlap” is built in so that at no time between segments are all LEDs completely OFF in the dot mode.

Generally 1 LED fades in while the other fades out over a mV or more of range

(1)

. The change may be much

more rapid between LED No. 10 of one device and LED No. 1 of a second device “chained” to the first.

The LM3914 features individually current regulated LED driver transistors. Further internal circuitry detects when

any driver transistor goes into saturation, and prevents other circuitry from drawing excess current. This results in

the ability of the LM3914 to drive and regulate LEDs powered from a pulsating DC power source, i.e., largely

unfiltered. (Due to possible oscillations at low voltages a nominal bypass capacitor consisting of a 2.2μF solid

tantalum connected from the pulsating LED supply to pin 2 of the LM3914 is recommended.) This ability to

operate with low or fluctuating voltages also allows the display driver to interface with logic circuitry, opto-coupled

solid-state relays, and low-current incandescent lamps.

Figure 15. Cascading LM3914s in Dot Mode

(1) Accuracy is measured referred to +10.000V

at pin 6, with 0.000 V

at pin 4. At lower full-scale voltages, buffer and comparator offset

voltage may add significant error.

Product Folder Links: LM3914