Programmable from 1µA to 10mA. □ ±3% initial accuracy. Description. The LM/LM/LM are 3-terminal adjustable current sources characterized by . LMM Texas Instruments Current & Power Monitors & Regulators NRND, alternate is LMM/NOPB datasheet, inventory, & pricing. LMM/NOPB Texas Instruments Current & Power Monitors & Regulators 3- TERM ADJ CURRENT SOURCE datasheet, inventory, & pricing.

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Kuba Ober 1, 10 The typical performance is shown in the datasheet in this graph:. In the case of the LM, it is rated with a voltage drop of 2.

The trip point is intended to be no higher than ohms per volt – 10k. This will vary over temperature and from unit to unit, that’s what they mean by ‘typical’.

From there, it’s just a matter of tuning either the set resistor of the LM or the voltage threshold to trim to the setpoint. The divider produces about 0. datashset

Remember that this circuit must act appropriately during faults – and then the LM is a short. Sign up using Email and Password. Can R3 be replaced with an opto-isolator diode and series resistor?

The question at hand is how best to detect when the voltage across the LM exceeds a threshold. You can increase the resistance of the divider if you can use a larger load resistor R3 or a higher-gain transistor.

Nope, it won’t work. I don’t see a way in circuitlab to represent an actual LM, so the simulation likely won’t operate correctly. If the load impedance is high, then the current will be much lower than datashedt limit.

So if the LM is connected low side and sinking 1mA, and you want to know when the forward voltage drops below 1V you can use a comparator with a 1V reference. Nov 13 ’15 at When the 1 mA of current is reached, it should begin to increase its resistance, thus increasing the voltage drop across it. At least, that’s my thinking at the present. Tyler Think of it rather as a current limiter. The typical performance is shown in the datasheet in this graph: I have an LM based constant current source configured to supply a max of 1 mA.


The load has a lj334m impedance. Furthermore, I think datasheeet rather crazy that you allow such high ground impedance 10k. The simplest way to detect that would be by biasing a PNP transistor with a scaled-down version of the drop out voltage. So what you do is connect R2 directly between L and PE terminals.

If the voltage is more than 2. The LM in this case does not have an infinite voltage with which to overcome the load impedance.

LMM/NOPB – Texas Instruments – PCB Footprint & Symbol Download

When it’s passing less than 1 mA of current, I would expect it to be acting like a very low-value resistor, meaning that the voltage drop across it should be low. The reference could be derived from a regulated supply voltage such as 5V with a voltage divider. How to tell when an LM is limiting the current?

One option would be a TL or LMV, but that’s just one of an almost infinite number of possibilities. In the schematic, I1 represents the LM Usually when a current supplied less than the current required, there is a voltage drop. I’d like to measure the voltage drop and light an LED really an optoisolator when it exceeds a threshold.

National Semiconductor – datasheet pdf

Post as a guest Name. If it is a “constant” current source, why is the current “variable”? I need to use an opto between this circuit and the datasheeet systems for safety. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Dztasheet the load impedance is low, then the current will hit the limit.


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National Semiconductor

A small current from an AC supply is intentionally “leaked” to ground. The circuit in this case is a Ground Continuity Monitor. You need a different design, and I question the need for a current source. So if you monitor the voltage across the LM perhaps with a comparator you lm34m have a good idea of whether it is working or not. Sign up or log in Sign up using Google. It depends on GREATLY on how the LM is connected high side or low side, for example and how much your current is and datashheet much error you can tolerate any monitor circuit will lower the output impedance.

This isn’t superbly accurate, but xatasheet work well enough. My goal is to make an alarm of sorts when that impedance exceeds a threshold, and the way I want to do that is to detect when the is in current limiting mode.

Datasheet «LM334»

Home Questions Tags Users Unanswered. If anyone else has an idea of how to light an LED when an LM is actually limiting the l,334m through it, that would work too. If it’s less than that it may or may not be working there is no minimum voltage below which is it is guaranteed to not work.