0-10V(IP) dc to 0-3.3V(OP) dc analogue linear conversion circuit?

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i want to convert 0-10V in to 0-3.3V linearly for analogue input of STM32 MCU so for this application any op-amp circuit which can done this?

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Peter BENSCHBest answer

ST Technical Moderator

It depends on what you want to do with the output voltage: should it be measured or is it used for further processing with an internal comparator or opamp?

If it is to be measured: does it necessarily have to be converted to 3.3V, or can you also accept a lower output voltage?

To stay with the measurement: both have advantages and disadvantages:

If the maximum output voltage is the same as the reference voltage, you use the full range of the ADC, resulting in maximum resolution.
if the maximum output voltage is smaller than the reference voltage, you can correct the measurement result with a fixed factor, but this reduces the usable resolution

Let's assume for the sake of simplicity that you want to measure the signal converted from 10V to 3.3V. Then you can, for example, reduce the 10V to 3.3V with a voltage divider 67:10 (e.g. 68k+33k or a better optimized ratio), then buffer it with a Unity Gain Buffer Amplifier as described here in Wikipedia, fig 3, and then connect it to the ADC input.

If the opamp is supplied by VDD=3.3V, you have to make sure that it is a RRIO amplifier, i.e. rail-to-rail input and output, like e.g. TSZ121 or TZ181. Of course you can also use other types with a larger offset, but don't forget that the offset is an error in the output signal.

Good luck!

Regards

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

Peter BENSCHBest answer

ST Technical Moderator

It depends on what you want to do with the output voltage: should it be measured or is it used for further processing with an internal comparator or opamp?

If it is to be measured: does it necessarily have to be converted to 3.3V, or can you also accept a lower output voltage?

To stay with the measurement: both have advantages and disadvantages:

If the maximum output voltage is the same as the reference voltage, you use the full range of the ADC, resulting in maximum resolution.
if the maximum output voltage is smaller than the reference voltage, you can correct the measurement result with a fixed factor, but this reduces the usable resolution

Let's assume for the sake of simplicity that you want to measure the signal converted from 10V to 3.3V. Then you can, for example, reduce the 10V to 3.3V with a voltage divider 67:10 (e.g. 68k+33k or a better optimized ratio), then buffer it with a Unity Gain Buffer Amplifier as described here in Wikipedia, fig 3, and then connect it to the ADC input.

If the opamp is supplied by VDD=3.3V, you have to make sure that it is a RRIO amplifier, i.e. rail-to-rail input and output, like e.g. TSZ121 or TZ181. Of course you can also use other types with a larger offset, but don't forget that the offset is an error in the output signal.

Good luck!

Regards

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

Peter BENSCH

ST Technical Moderator

If the problem is resolved, please mark this topic as answered by selecting Select as best. This will help other users find that answer faster.

/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

parth kothiyaAuthor

Associate III

Can you please suggest me any circuit schemetic for this.

Voltage divider > voltage follower for importance matching.

If I want to add protection here op voltage is must between 0-3.3V because more than 3.3V STM32 ADC pin demage how can I add this protection any circuit schemetic?

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