Electronic Components Datasheet Search
  English  ▼

Delete All


Preview PDF Download HTML

LM3915 Datasheet(PDF) 10 Page - Texas Instruments

Part No. LM3915
Description  LM3915 Dot/Bar Display Driver
Download  31 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Manufacturer  TI [Texas Instruments]
Direct Link  http://www.ti.com
Logo TI - Texas Instruments

LM3915 Datasheet(HTML) 10 Page - Texas Instruments

Back Button LM3915 Datasheet HTML 6Page - Texas Instruments LM3915 Datasheet HTML 7Page - Texas Instruments LM3915 Datasheet HTML 8Page - Texas Instruments LM3915 Datasheet HTML 9Page - Texas Instruments LM3915 Datasheet HTML 10Page - Texas Instruments LM3915 Datasheet HTML 11Page - Texas Instruments LM3915 Datasheet HTML 12Page - Texas Instruments LM3915 Datasheet HTML 13Page - Texas Instruments LM3915 Datasheet HTML 14Page - Texas Instruments Next Button
Zoom Inzoom in Zoom Outzoom out
 10 / 31 page
background image
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+ for bar mode and more than 200 mV below V+ (or open circuit) for dot mode. In most
applications, pin 9 is either open (dot mode) or tied to V+ (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.
In order for the display to make sense when multiple LM3915s 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 below.
As long as the input signal voltage is below the threshold of the second LM3915, LED #11 is off. Pin 9 of
LM3915 #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 LM3915 #1 is pulled an LED drop (1.5V or more) below VLED. This condition is
sensed by comparator C2, referenced 600 mV below VLED. This forces the output of C2 low, which shuts off
output transistor Q2, extinguishing LED #10.
VLED is sensed via the 20k resistor connected to pin 11. The 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 LM3915 #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 with a 10k resistor. The 1V IR 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.
The LM3915 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 1.6 mA. However, any reference
loading adds 4 times that current drain to the V+ (pin 3) supply input. For example, an LM3916 with a 1 mA
reference pin load (1.3k) would supply almost 10 mA to every LED while drawing only 10 mA from its V+ 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 are all segments completely off in the dot mode. Generally 1 LED
fades in while the other fades out over a mV or more of range. The change may be much more rapid between
LED #10 of one device and LED #1 of a second device “chained” to the first.
Application Hints
The most difficult problem occurs when large LED currents are being drawn, especially in bar graph mode.
These currents flowing out of the ground pin cause voltage drops in external wiring, and thus errors and
oscillations. Bringing the return wires from signal sources, reference ground and bottom of the resistor string to a
single point very near pin 2 is the best solution.
Long wires from VLED to LED anode common can cause oscillations. Depending on the severity of the problem
μF to 2.2 μF decoupling capacitors from LED anode common to pin 2 will damp the circuit. If LED anode
line wiring is inaccessible, often similar decoupling from pin 1 to pin 2 will be sufficient.
If LED turn ON seems slow (bar mode) or several LEDs light (dot mode), oscillation or excessive noise is usually
the problem. In cases where proper wiring and bypassing fail to stop oscillations, V+ voltage at pin 3 is usually
below suggested limits. Expanded scale meter applications may have one or both ends of the internal voltage
divider terminated at relatively high value resistors. These high-impedance ends should be bypassed to pin 2
with at least a 0.001
μF capacitor, or up to 0.1 μF in noisy environments.
Submit Documentation Feedback
Copyright © 2000–2013, Texas Instruments Incorporated
Product Folder Links: LM3915

Similar Part No. - LM3915

ManufacturerPart No.DatasheetDescription
National Semiconductor (TI)
National Semiconductor ...
LM3915 NSC-LM3915 Datasheet
1Mb / 25P
   Dot/Bar Display Driver
LM3915N NSC-LM3915N Datasheet
1Mb / 25P
   Dot/Bar Display Driver
LM3915N-1 NSC-LM3915N-1 Datasheet
1Mb / 25P
   Dot/Bar Display Driver
Texas Instruments
Texas Instruments
LM3915N-1 TI1-LM3915N-1 Datasheet
1Mb / 31P
[Old version datasheet]   LM3915 Dot/Bar Display Driver
LM3915N-1/NOPB TI1-LM3915N-1/NOPB Datasheet
1Mb / 31P
[Old version datasheet]   LM3915 Dot/Bar Display Driver
More results

Similar Description - LM3915

ManufacturerPart No.DatasheetDescription
Texas Instruments
Texas Instruments
LM3915N-1 TI1-LM3915N-1 Datasheet
1Mb / 31P
[Old version datasheet]   LM3915 Dot/Bar Display Driver
National Semiconductor (TI)
National Semiconductor ...
LM3915 NSC-LM3915 Datasheet
1Mb / 25P
   Dot/Bar Display Driver
LM3916 NSC-LM3916 Datasheet
509Kb / 27P
   Dot/Bar Display Driver
LM3914 NSC-LM3914 Datasheet
365Kb / 19P
   Dot/Bar Display Driver
LM3914 NSC-LM3914_03 Datasheet
809Kb / 22P
   Dot/Bar Display Driver
Texas Instruments
Texas Instruments
LM3914N-1 TI1-LM3914N-1 Datasheet
790Kb / 29P
[Old version datasheet]   LM3914 Dot/Bar Display Driver
LM3916 TI1-LM3916 Datasheet
1Mb / 32P
[Old version datasheet]   LM3916 Dot/Bar Display Driver
NTE Electronics
NTE Electronics
NTE1549 NTE-NTE1549 Datasheet
29Kb / 4P
   Integrated Circuit Dot/Bar Display Driver
NTE1508 NTE-NTE1508 Datasheet
31Kb / 3P
   Integrated Circuit 10-Step Dot/Bar Display Driver for Linear Scale
NTE1509 NTE-NTE1509 Datasheet
30Kb / 4P
   Integrated Circuit 10-Step Dot/Bar Display Driver for Logarithmic Scale
More results

Html Pages

1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31 

Datasheet Download

Go To PDF Page

Link URL

Privacy Policy
Does ALLDATASHEET help your business so far?  [ DONATE ] 

About Alldatasheet   |   Advertisement   |   Datasheet Upload   |   Contact us   |   Privacy Policy   |   Link Exchange   |   Manufacturer List
All Rights Reserved©Alldatasheet.com

Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz