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| LM317 digital control |
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| Maobuff:
Im working on my own power supply project. I want to control output voltage of LM317 via microcontroller (PWM or DAC). Can some one help me with it? |
| jdraughn:
All the datasheets I have seen for the LM317 cover this. The schematic shows a few transistors which pull different value resistors to ground to change the output voltage. You could get 256 values with 8 transistors. Using a buffered DAC would give you finer control with less parts. |
| danadak:
One limitation of the DAC approach is the min output voltage of a LM317 will be ~ >-1.25V, its reference voltage. On way of handling this is an OpAmp summer, operating off split supplies, with 2 inputs, DAC and an offset you generate of 1.25V. Regards, Dana. |
| Maobuff:
--- Quote from: jdraughn on May 19, 2016, 10:20:16 am ---All the datasheets I have seen for the LM317 cover this. The schematic shows a few transistors which pull different value resistors to ground to change the output voltage. You could get 256 values with 8 transistors. Using a buffered DAC would give you finer control with less parts. --- End quote --- Can you show a circuit for solution with dac |
| danadak:
Very simple. take the V output of the DAC and tie it to the LM317 ref pin. Regards, Dana. |
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