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| High precision voltage regulator? |
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| BiOzZ:
I need to make a ~10-50 PPM voltage reference that works from 0v to 12v and can pass 1.5A (output will go to 1.2A but i want some buffer) i was wondering if there is any high precision equivalent to a LM317? i have a -12v rail, 15v rail and a 5v rail to work with, there is an LT1236S 5ppm 1.2v reference on circuit and i have an extra OP2333 0.05 ?V/°C "0 drift" (chopper) amp running on the 5v rail i can use I'm just making one for me so i can easily add in any components necessary but i was considering making my own with a fet and a good opamp and the reference but im worried about stability problems |
| dannyf:
I think you will find a lot more help if you lay out what you are trying to do and why you think you need such a beast. There are reasons certain products don't exist or are rare / expensive to find. |
| BiOzZ:
--- Quote from: dannyf on January 17, 2014, 01:34:33 pm ---I think you will find a lot more help if you lay out what you are trying to do and why you think you need such a beast. There are reasons certain products don't exist or are rare / expensive to find. --- End quote --- Nah i already found one ... basically an LM317 with an external reference and capable of 35ppm for only $12 |
| sync:
btw: what do you want to achieve? 50ppm and 1.2A? 12V * 50ppm = 0.6mV 0.6mV / 1.2A = 0.5mOhm So the resistance between your sense point and the load must be (way) smaller that 0.5mOhm. |
| PedroDaGr8:
--- Quote from: BiOzZ on January 16, 2014, 08:36:37 pm ---I need to make a ~10-50 PPM voltage reference that works from 0v to 12v and can pass 1.5A (output will go to 1.2A but i want some buffer) i was wondering if there is any high precision equivalent to a LM317? i have a -12v rail, 15v rail and a 5v rail to work with, there is an LT1236S 5ppm 1.2v reference on circuit and i have an extra OP2333 0.05 ?V/°C "0 drift" (chopper) amp running on the 5v rail i can use I'm just making one for me so i can easily add in any components necessary but i was considering making my own with a fet and a good opamp and the reference but im worried about stability problems --- End quote --- Sorry but this is not the easy task you claim. It's one thing to get 50ppm accuracy at one point in time. When you are dealing with PPM you can't just specify output accuracy. You mention nothing about load regulation, line regulation, temp coefficient, etc. So while you MIGHT (and I'm being generous here) be able to meet your specs at a single input voltage, at a single temp, etc. You will NOT NOT NOT easily be able to meet them under even more normal conditions; let alone extremes. Anyone that claims you can use an LT317 or similar to get 50ppm accuracy is not being honest. Just because something is on the internet The temperature coefficient alone PER DEGREE CELSIUS is larger than your requested 50ppm (around 100ppm/oC based on the datasheet). Factor in line regulation, thermal regulation (variance from self heating), load regulation and there is no way you are getting 50ppm accuracy from an LT317. |
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