What is the functionality of the LM3914V driver?

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Discussion Overview

The discussion revolves around the functionality of the LM3914V driver, specifically its operation in lighting LEDs based on varying input voltage levels. Participants explore its behavior in different modes, such as a VU meter and as a set of window comparators, while considering its internal structure and potential applications.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants describe the LM3914V as capable of lighting all LEDs on a rising input, similar to a VU meter, or lighting one LED at a time based on specific voltage ranges.
  • There is a suggestion that the chip may utilize parallel comparators referenced to the next voltage level, with an enable or high-Z pin in the schematic.
  • One participant proposes that the chip contains a string of comparators with reference voltages derived from a potential divider across the supply, noting issues with power consumption and stability in bar graph mode.
  • Another participant elaborates on the operation of the chip, suggesting that comparators check the input voltage against reference voltages and that XOR gates may be used to activate a single LED in one LED mode.
  • A participant questions the clarity of the initial inquiry, asserting that the datasheet provides sufficient information about the chip's comparator structure.

Areas of Agreement / Disagreement

Participants express varying interpretations of the LM3914V's functionality, with some agreeing on its comparator-based design while others question the clarity of the initial question. No consensus is reached regarding the specifics of its operation or the best mode of use.

Contextual Notes

Participants reference the datasheet for technical details, but there are indications of uncertainty regarding the chip's power consumption and stability in different modes. The discussion includes assumptions about the internal workings of the chip that are not fully resolved.

GUOJINMIAO
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TL;DR
LM3914V is a chip that drives 10 LED-based on linear input voltage values.
Hi , all!
The LM3914 can light all LEDs/activate all outputs on a rising input similar to a VU meter kind of thing or function more like a set of window comparators and only light one LED/activate one output at a time, e.g. 1V to 2V input is only output 1 on, 2V to 3V input is output 2 on but 1 off, 3V to 4V input is output 3 on but 1 and 2 off, and so on. Is it right?
But I tried to think about it, Maybe parallel comparators referenced to the next reference voltage up or something? An enable/high Z pin on the comparators in the simplified schematic? Bar mode is easy to simulate, it's the same circuit as the simplified schematic.
Do any amazing people know about this? Thanks

[Moderator Note: Post has been edited to delete a questionable link. Here is a more generic link to the datasheet]

https://www.ti.com/product/LM3914?keyMatch=LM3914
 
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GUOJINMIAO said:
Summary:: LM3914V is a chip that drives 10 LED-based on linear input voltage values.

Hi , all!
Thehttps://www.utmel.com/components/lm3914v-driver-alternatives-pinout-datasheet?id=328 can light all LEDs/activate all outputs on a rising input similar to a VU meter kind of thing or function more like a set of window comparators and only light one LED/activate one output at a time, e.g. 1V to 2V input is only output 1 on, 2V to 3V input is output 2 on but 1 off, 3V to 4V input is output 3 on but 1 and 2 off, and so on. Is it right?
But I tried to think about it, Maybe parallel comparators referenced to the next reference voltage up or something? An enable/high Z pin on the comparators in the simplified schematic? Bar mode is easy to simulate, it's the same circuit as the simplified schematic.
Do any amazing people know about this? Thanks
I think the chip has a string of comparators and the reference for each is taken from a string of resistors forming a potential divider across the supply. I think the data sheet gives the schematic. I found the bar graph display a bit power hungry and also tended to be unstable. I have used both the linear version and the log version, and I have also used the chip as an A to D converter to demonstrate pulse code modulation using 4 bit coding.
 
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GUOJINMIAO said:
Maybe parallel comparators referenced to the next reference voltage up or something?
A column of series resistors provide reference voltages spaced between Rhi and Rlo.
Comparators check the input voltage Vin, against all the reference voltages.

In one LED only mode, the digital outputs of adjacent comparators go to XOR gates that turn on the LED where the comparator outputs are different. Rather than a bar, that will show only one LED on.
 
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