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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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The load has a variable impedance. One option would be a TL or LMV, but that’s just one of an almost infinite number of possibilities. The typical performance is shown in the datasheet in this graph: It depends on GREATLY on how the LM is connected high side or low side, for example and how much your current is and how much error you can tolerate any monitor circuit will lower the output impedance. 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.

It belongs in the question. A couple of resistors and a comparator with built-in reference would do the job in a much simpler fashion.

By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. If the load impedance is low, then the current will hit the limit. I have an LM based constant current source configured to supply a max of 1 mA.

The simplest way to datasgeet that would be by biasing a Datasheeg transistor with a scaled-down version of the drop out voltage. Furthermore, I think it’s rather crazy that you allow such high ground impedance 10k. I’d expect it to be minimal, however, since the should be trying to pass as lm334 current as it possibly can.


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. R2 completely determines the behavior of the system, when looked at from outside, and sets the leakage current. Nov 13 ’15 at 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’. 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. A small current from an AC supply is intentionally “leaked” to ground. The intent now is to connect the output to ground and measure the voltage drop across it instead. Home Questions Tags Users Unanswered.

Any real current source will have a voltage limit beyond which it will not deliver a constant current. In the datasheft circuit, the output drives an optoisolator’s LED, but that circuit isn’t accurate or sensitive enough.

LMM datasheet, Pinout ,application circuits 3-Terminal Adjustable Current Source

In the case of the LM, it is rated with a voltage drop of 2. If it is a “constant” current source, why is the current “variable”? Sign up using Email and Password.

The divider produces about 0. The typical performance is shown in the datasheet in this graph:. So what you do is connect R2 directly between L and PE terminals.

So if you monitor the voltage across the LM perhaps with a comparator you can have a good idea of whether it is working or not. Sign datazheet or log in Sign up using Google. The actual earth is on the far side of R1. I need to use an opto between this circuit and the logic systems for safety.


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. By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies. The reference could be derived from a regulated supply voltage such as 5V with a voltage divider.

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The comparator could be something like half an LM You need a different design, and I question the need for a current source. The circuit in this case is a Ground Continuity Monitor. How to tell when an LM is limiting the current? All of that is true.

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

Tyler Think of it rather as a current limiter. It’s not possible to give a good answer without much more information such as a complete schematic and accuracy requirements. Kuba Ober 1, 10 Post as a guest Name. Can R3 be replaced with an opto-isolator diode and series resistor? It’s also intended to at least attempt to desensitize the circuit datashete the tolerance variation of the k resistor and the supply voltage.