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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3-Terminal Adjustable Current Source

dataheet In the schematic, I1 represents the LM If anyone else has an idea of how to light an LED when an LM is actually limiting the current through it, that would work too.

It’s not possible to give a good answer without much more information such as a complete schematic and accuracy requirements.

Nope, it won’t work. When the 1 mA of current is reached, it should begin to increase its resistance, thus increasing the voltage drop across it.

One option would be a TL or LMV, but that’s just one of an almost infinite number of possibilities. You need a different design, and I question the need for a current source. Furthermore, I l334m it’s rather crazy dztasheet you datasehet such high ground impedance 10k.

In the case of the LM, it is rated with a voltage drop of 2. Home Questions Tags Users Unanswered. I need to use an opto between this circuit and the logic systems for safety. Can R3 be replaced with an opto-isolator diode and series resistor? R2 completely determines the behavior of the system, when looked at from outside, and sets the leakage current. The load has a variable impedance. I’d like to measure the voltage drop and light an LED really an optoisolator when it exceeds a threshold.

I have an LM based constant current source configured to supply a max of 1 mA. 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.

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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. The comparator could be something like half an LM Note as well that the actual circuit ground is on the top side of R1 – Vout is the ground potential for the purpose of this circuit.

Nov 13 ’15 at R1 represents the ground impedance – the goal is to detect when it’s value exceeds 10k.

Sign up using Email dataaheet Password. The LM in this case does not have an infinite voltage with which to overcome the load impedance. So for low currents, it might be delivering more-or-less constant current at 0.

Any real current source will have a voltage limit beyond which it will not deliver a constant current. All of that is true. It’s also intended to at least attempt to desensitize the circuit to the tolerance variation of the k resistor and the supply voltage.

At 25C, the LM has a minimal drop-out voltage of about 0. At least, that’s my thinking at the present. I’d expect it to be minimal, however, since the should be trying to pass as much current as it possibly can.

Sign up or log in Sign up using Google. The divider produces about 0.

LMM Datasheet(PDF) – National Semiconductor (TI)

The circuit in this case is a Ground Continuity Monitor. The reference could be derived from a regulated supply voltage such as 5V with a voltage divider. Post Your Answer Discard 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. 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.


Please edit your question and delete the comment. The typical performance is shown in the datasheet in this graph: In the old circuit, the output drives an optoisolator’s LED, but that circuit isn’t accurate or sensitive enough.

So what you do is connect R2 directly between L and PE terminals.

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. 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.

How to tell when an LM dafasheet limiting the current?

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

Email Required, but never shown. If that current doesn’t flow, then that’s an error. A couple of resistors and a comparator with built-in reference would do the job in a much simpler fashion. The intent now is to connect the output to ground and measure the voltage drop across it instead. Post as a guest Name. Othewise, the load is getting the maximum voltage that the source can provide, and is not running at full lm34m. 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 datashwet reference.

The typical performance is shown in the datasheet in this graph:. Sign up using Facebook. If the load impedance is low, then the current will hit the limit. Usually datsheet a current supplied less than the current required, there is a voltage drop. If the voltage is more than 2.