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How to get multiple output voltages from LDO + BG noise (chopper stabilization)

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!! the phoenix law !!

Member level 1
Nov 28, 2010
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I have 2 questions
1- I have designed a LDO regulator with 1.8v output voltage, now I need also 1.2v and 0.9v, is there any possible way to drive them from my LDO ? something like multiple outputs LDO ? if not, can anyone suggest another solution ?
2- The BG which I have designed for my LDO has a little high noise level, I heard about chopper stabilization but I can't find any related info or examples, so can someone help me with this too ?
Thx Guys

If every channel needs current driving, you need several LDOs. However, reference block can be shared.

For chopping, just switch the input differential stage and second gain stage. It will cancel offset of input stage.
Then a low pass filter is added to filter the switching noise.

1. It's easy to attain multiple outputs LDO by splitting your feedback resistors rationally, and you will get .9V of divided voltage from 1.2V output.

2. If it's convenient, pls attach your BG schematic.

Yes, every channel needs current driving, but the problem is:
The BG output is 1.28v, how to make the LDO output less ? 1.2v or 0.9v ?
The feedback value is larger than the output ?!! is this possible ? how ?

I found a good tutorial on chopping, I will try to follow it and ask if something was unclear

Use a buffer to divide 1.28 to lower voltage reference.
0.5V is an example.

Use a voltage buffer to generate 0.5V voltage reference.
Then, use 0.5V voltage reference for LDO to generate 0.9v or 1.2v output voltage with strong driving capability.

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