# Tag Info

### This LM317 diagram doesn't make any sense to me

The datasheet has a pretty thorough description of the use of the ADJ pin with $R_1$ and $R_2$: Since both $R_1$ and $R_2$ appear in the equation for the output voltage V_{\text{out}} = 1....
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### This LM317 diagram doesn't make any sense to me

Overview I'll avoid depending upon algebra as an explanation. (Because algebra, while providing quantitative answers, doesn't often help people understand something unless they are very fluent with ...
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### Smartest way to use current limit using LM317?

See LM317 based power supply with current limiting on SE and alexan_e's answer. Read through all the answers and comments as there were some good suggestions. The circuit avoids high-current pots by ...
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### LM317 µA Constant Current source possibility?

Yes, that is clever, I think it would 'work', however the problem is that Iadj is 50-100uA so that you will not be able to get an accurate load current. First, it is large, so your 200uA current might ...
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### LM317T with weird pinout?

Neither of your circuits is correct. The correct circuit looks like this: simulate this circuit – Schematic created using CircuitLab If you connect it incorrectly (as in the first circuit) it ...
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### 12 V lead acid charger with LM317 not charging

Read the datasheet of the LM317, on page 9 it states: So when you feed the LM317 14 V it can regulate to 11 V and lower, not 13.5 V. Also there will be 1.25 V across R1 so for 13.5 V you will need ...
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### LM317s in parallel connection

Yes, it is possible. Do not connect the outputs directly together but rather put a small resistor (0.5 Ohm or so) between each output and the summing node. Check: http://www.ti.com/lit/ds/symlink/...
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### Does the LM317 take ANY voltage and convert it into the adjusted one?

The 317's valid input voltage range is from a minimum of 3 V above its programmed output, to a maximum of 40 V (32 V for some types). Within that range, it will provide approximately the programmed ...
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### LM317T not working properly?

It's a linear regulator. It can only decrease voltage, cap it, as you've said. It is working appropriately as you've described it. If you want to be able to go up or down from the input voltage you ...
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No, this won't work to give you +/- supplies, because of the common negative rail. You can, however, use the transformer you have to give you +/- adjustable supplies by using two half-wave ...
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### Cheap switch-mode regulator "comparable" to LM317

Here is a quite short list of TI's Buck/Boost converters which have PDIP packaging. There are only 2 of 33 DC-DC converters which are available with though-hole package , and the only difference of ...
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### Cheap switch-mode regulator "comparable" to LM317

I would take a close look at the National Semiconductor (now TI) LM2575 family. Very, Very easy to use. LM2575: 1 Amp buck converter LM2576: 3 Amp buck converter I would suggest a couple of ...
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### lm317 current source

True, but irrelevant in your case. An LED does not change forward voltage quickly- there is a slow (thermal) change, but nothing on the order of microseconds where the caps have some effect. The caps ...
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### Puzzled with the result of LM317 constant current

If your LED lamp assembly is 10W at 900mA it needs about 11.1V to operate. The LM317 current source needs 1.25V in the resistor and a further 3V headroom to operate, put it all together and your ...
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### High Side Constant Current Source

You can use this idea: - The voltage across R1 sets the voltage that is forced across R2 by the op-amp's negative feedback. Let's say that voltage is 0.1 volts and let's say R2 is 1 ohm. This means ...
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### multi-tap transformer relay for LM317 tips

simulate this circuit – Schematic created using CircuitLab Figure 1. Transformer tap selector. This isn't a complete answer but will give you some ideas to work on. Whatever electronic ...
• 161k
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### LTspice model for LM317 and the calculators gives different output voltages for the same resistors values

The correct nominal voltage according to datasheet calculations is 9.138V (min 8.775, maximum 9.50 resulting from the reference voltage tolerance, ignoring resistor tolerances and adjust current ...
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### Voltage drop with 2 LM317 in parallel/different output voltages

Since the outputs are independent 5.1 V and 4 V supplies then the LM317s know nothing about each other. Each device needs a supply that is 2.5 V higher than the output so one needs ≥ 7.6 V and the ...
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