ahsan_i_h
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hello everybody,
A flaw in LM317 circuit is found which is generally availabe in internet. I need varification by everyone.
There is a resistor between LM317's output and adjust. It has a maximum value. It must not go higher than 240 ohm for LM117 and must not go higher than 120 ohm for LM317. In general internet circuits, 240 ohms is shown as the maximum limit for LM317 circuits. That is the problem.
Lets calculate to prove, The minimum load current of LM117 is 5mA(datasheet), so the maximum value of that resister is 1.2v/5mA=240 ohms. But the minimum load current of LM317 is 10mA(datasheet), so the maximum value of that resistor should be 1.2v/10mA=120 ohms.
In national semiconductor datasheet all the circuits are drawn with LM117. I think, that diagrams misleaded the general internet circuits and made thinking LM317 as LM117.
About the flaw am I right? or may be I am thinking wrong or missing something?
A flaw in LM317 circuit is found which is generally availabe in internet. I need varification by everyone.
There is a resistor between LM317's output and adjust. It has a maximum value. It must not go higher than 240 ohm for LM117 and must not go higher than 120 ohm for LM317. In general internet circuits, 240 ohms is shown as the maximum limit for LM317 circuits. That is the problem.
Lets calculate to prove, The minimum load current of LM117 is 5mA(datasheet), so the maximum value of that resister is 1.2v/5mA=240 ohms. But the minimum load current of LM317 is 10mA(datasheet), so the maximum value of that resistor should be 1.2v/10mA=120 ohms.
In national semiconductor datasheet all the circuits are drawn with LM117. I think, that diagrams misleaded the general internet circuits and made thinking LM317 as LM117.
About the flaw am I right? or may be I am thinking wrong or missing something?