LM3915

Manufacturer Part NumberLM3915
ManufacturerTexas Instruments
LM3915 datasheet
 


Specifications of LM3915

Output Channels10Led Voltage(max)(v)17
Pin/package18PDIPRegulated Outputs(#)10
Iout(max)(a)0.03Led ConfigurationParallel
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LM3915
LM3915 Dot/Bar Display Driver
Literature Number: SNVS740B

LM3915 Summary of contents

  • Page 1

    ... LM3915 LM3915 Dot/Bar Display Driver Literature Number: SNVS740B ...

  • Page 2

    ... 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 LM3915 is rated for operation from 0˚C to +70˚C. The LM3915N-1 is available in an 18-lead molded DIP package. DS005104 February 2001 ± ...

  • Page 3

    Typical Applications 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. www.national.com 0V to 10V ...

  • Page 4

    Absolute Maximum Ratings 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) Supply Voltage Voltage on Output Drivers Electrical Characteristics Parameter COMPARATOR Offset Voltage, Buffer ...

  • Page 5

    ... Note 5: Bar mode results when pin 9 is within disabled if pin 9 is pulled 0.9V or more below V Note 6: The maximum junction temperature of the LM3915 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). ...

  • Page 6

    Typical Performance Characteristics Supply Current vs Temperature Reference Voltage vs Temperature LED Current-Regulation Dropout Operating Input Bias Current vs Temperature 00510434 Current vs Temperature 00510436 LED Driver Saturation 00510438 5 00510435 Reference Adjust Pin 00510437 Voltage 00510439 www.national.com ...

  • Page 7

    Typical Performance Characteristics Input Current Beyond Signal Range (Pin 5) LED Driver Current Regulation Common-Mode Limits www.national.com (Continued) 00510440 Total Divider Resistance 00510442 Output Characteristics 00510444 6 LED Current vs Reference Loading 00510441 vs Temperature 00510443 00510445 ...

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    Block Diagram (Showing Simplest Application) 7 00510404 www.national.com ...

  • Page 9

    ... LM3915 driver. Continue connecting pin 9 of lower input drivers to pin 1 of higher input drivers for 30 or more LED displays. The last LM3915 driver in the chain will have pin 9 left open. All previous drivers should have a 20k resistor in parallel with LED #9 (pin ...

  • Page 10

    ... 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 ...

  • Page 11

    ... Figure 1 uses a PNP emitter-follower in front of the diode. Now, the transistor’s base-emitter voltage cancels out the diode offset, within about 100 mV. This approach is usually satisfactory when a single LM3915 is used for display. Display circuits using two or more LM3915s for a dynamic range greater require more accurate detection ...

  • Page 12

    ... A better approach shown in Figure keep the reference at 10V for both LM3915s and amplify the input signal to the lower LM3915 by 30 dB. Since two 1% resistors can set the amplifier gain within ...

  • Page 13

    ... To extend this approach to get display, another amplification must be placed in the signal path ahead of the lowest LM3915. Extreme care is required as the lowest LM3915 displays input signals down to 0.5 mV! Sev- eral offset nulls may be required. High currents should not share the same path as the low level signal ...

  • Page 14

    ... FIGURE 7. Design Equations for Fixed LED Intensity separate channels for stereo. This technique can be ex- tended for larger numbers of LM3915s by varying the values of R1, R2 and R3 in inverse proportion to the number of devices tied in. The ICs’ internal references track within 100 mV so that worst case error from chip to chip is only 0 ...

  • Page 15

    ... 10V LED REF FIGURE 9. Independent Adjustment of Reference Voltage and LED Intensity for Multiple LM3915s The scheme in Figure 10 is useful when the reference and LED intensity must be adjusted independently over a wide range. The R voltage can be adjusted from 1.2V to 10V HI with no effect on LED current. Since the internal divider here does not load down the reference, minimum LED current is much lower ...

  • Page 16

    ... Typical Applications *Optional circuit for improved intensity matching at low currents. See text. FIGURE 10. Wide-Range Adjustment of Reference Voltage and LED Intensity for Multiple LM3915s FIGURE 11 10V Log Display with Smooth Transitions 00510419 15 00510418 www.national.com ...

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    Typical Applications This application shows that the LED supply requires minimal filtering. *See Application Hints for optional Peak or Average Detector. † Adjust R3 for 3 dB difference between LED #11 and LED #12. LED Threshold ...

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    Typical Applications (Continued) Indicator and Alarm, Full-Scale Changes Display from Dot to Bar *The input to the dot bar switch may be taken from cathodes of other LEDs. Display will change to bar as soon as the LED so selected ...

  • Page 19

    Typical Applications ± R7 thru R15: 10k 10% D1, D2: 1N914 or 1N4148 *Half-wave peak detector. See Application Hints. Supply current drain is only 15 mA with ten LEDs illuminated. www.national.com (Continued) Driving Vacuum Fluorescent Display Low Current Bar Mode ...

  • Page 20

    Typical Applications (Continued) Full-scale causes the full bar display to flash. If the junction of R1 and C1 is connected to a different LED cathode, the display will flash when that LED lights, and at any higher input signal. Driving ...

  • Page 21

    Typical Applications Logarithmic response allows coarse and fine adjustments without changing scale. Resolution ranges from 500 www.national.com (Continued) Precision Null Meter ± = 1.25V 00510428 ...

  • Page 22

    ... Operating with a High Voltage Supply (Dot Mode Only) The LED currents are approximately 10 mA, and the LM3915 outputs operate in saturation for minimum dissipation. *This point is partially regulated and decreases in voltage with temperature. Voltage requirements of the LM3915 also decrease with temperature. *Resistor value selects exposure ...

  • Page 23

    Typical Applications Load Impedance 4Ω 8Ω 16Ω www.national.com (Continued) Audio Power Meter R1 10k 18k 30k 22 00510431 See Application Hints for optional Peak or Average Detector ...

  • Page 24

    ... Dual-in-Line Package Top View Order Number LM3915N-1 See NS Package Number NA18A Order Number LM3915N * See NS Package Number N18A *Discontinued, Life Time Buy date 12/20/99 sured 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 ...

  • Page 25

    ... Note: Unless otherwise specified. 1. Standard Lead Finish: 200 microinches /5.08 micrometer minimum lead/tin 37/63 or 15/85 on alloy 42 or equivalent or copper 2. Reference JEDEC registration MS-001, Variation AC, dated May 1993. www.national.com inches (millimeters) unless otherwise noted Molded Dual-In-Line Package (N) Order Number LM3915N-1 NS Package Number NA18A 24 ...

  • Page 26

    ... Deutsch Tel: +49 (0) 69 9508 6208 English www.national.com Français Tel: +33 ( 8790 Molded Dual-In-Line Package (N) Order Number LM3915N * NS Package Number N18A *Discontinued, Life Time Buy date 12/20/ critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system affect its safety or effectiveness ...

  • Page 27

    ... Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’ ...