LM117 3.3V PDF

Buy LMMP – TEXAS INSTRUMENTS – Fixed LDO Voltage Regulator, 15V in, V Dropout, V/mA out, SOT at Farnell element order. The ohm resistor is only required for the V version of the LD to maintain minimum regulation, with a 10 mA minimum load. This is the basic LDV33 voltage regulator, a low drop positive regulator with a V fixed output voltage. This fixed regulator provides a great amount.

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So efficiency must be lower than the maximum possible in most cases. JGord – Did your comment end up on the wrong post?

3.3V Regulator Board Using LM1117-3.3V IC

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The datasheet has a spec section for multiple output voltages. Either a lower value of R1 must be used or a minimum external load suitable to bring the total up to at least 10 mA must always be present. This doesn’t have much of anything to do with an op-amp.

That saida ohm resistor is only a 27 mA load at 3. Home Questions Tags Users Unanswered.

V Regulator Board Using LMV IC – Circuit Ideas I Projects I Schematics I Robotics

With R1 set, R2 can now be dimensioned to achieve the desired output voltage. Changed my answer to accomodate. When I follow the circuit, I am getting Vout as 3. SO the ohm resistor shown for R1 would not meet the LM minimum load requirement worst case. 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.

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When ‘designing” a circuit rather than just “making it work” it is essential that the worst case parameters are used.

voltage – Resistors values to use with LM – Electrical Engineering Stack Exchange

km117 You may need a larger input capacitor depending on how far away your power supply is. When I remove the resistor, I am getting the expected Vout 3. A maximum minimum is a nice concept: See the V O spec on the datasheet, for the 3. If R2 is large then the change in .33v through R2 under load may be significant.

When I remove the resistor and leave the capacitors, it does go back to 3.

AdrianMaire 5 uA is correct in this context. The datasheet mentions a minimum load of 3. We get a simplified equation then:. If it was then you should om117 not be using a simple 3 terminal regulator, but that’s another story.

Dropout can be as low as 1V at 20 mA at C!!! Resistors values to use with LM Ask Question.

It’s given by the following equation: As this remains constant at all times, but the I through R1 changes depending on it’s resistance, you need to make sure that the uA is not a large part of the program current. It’s better to choose 10mA, not only because you always have to calculate for 3.3b case, but also because the 10mA is given as a minimum condition for the other parameters.

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The LM internal electronics are “operated” by the dropout voltage across the regulator and a minimim current MUST flow through the regulator to achieve regulation.

So the higher you have R1, the more “error” Iadj will cause, as it starts to become a significant part of the overall current.

This is a great detailed description. Post as a guest Name. 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.

Sign up or log in Sign up using Google. Where Vin is more than about 2V above Vout it is the regulators job to drop the excess voltage. You also have to take into account Iadj, which is around uA. Make sure your capacitors are as close to the LDO as possible.

There is a second less subtle but sometimes overlooked factor. I know that ratio R1 to R2 determine the output voltage of LM In other situations your load may include a LED or so which already draws twice the required current. Sign up using Email and Password. What is the impact of increasing the resistors lk117 but keeping the ratio the same?

Worst case, with no load, R1 provides a convenient way of providing the 10 mA while also providing a nicely “stiff” divider.

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