How can we achieve the highest level of stability for the voltage that powers the microcontroller?

QWE4562009

How can we achieve the highest level of stability for the voltage that powers the microcontroller? [Copy link]

 

How to achieve the highest level of stability for the voltage supplying the microcontroller? For example, 3.3V, add some capacitors after the LDO output. Generally, it is 10uF+0.1uF. What other methods can be used to improve the stability of the power supply for the microcontroller? Because the microcontroller needs ADC sampling (the internal reference of the microcontroller is used as a reference), and some sensors also require very accurate and stable voltages

damiaa

This is mainly to consider the ripple.

If there is a lot of external interference, EMC should also be considered.

dcexpert

For ADC to have high precision, it cannot rely on VCC and requires an independent reference.

dql2016

Use low ripple LDO

秦天qintian0303

The ripple of LDO is generally not large. One way is to use an independent reference. In terms of power supply, the LDO must not be connected to other devices with high power requirements.

Honghuzaitian

dcexpert posted on 2022-10-13 17:29 ADC cannot rely on VCC for high precision, and requires an independent reference.

Yes, if the reference source is very stable and accurate, the general ADC will be similar, and the accuracy of the ADC must also be high. Otherwise, if your accuracy is greater than the power supply jitter, it will be useless to have a good reference source.

bigbat

From my personal experience, except for TI, NXP, and ST chips, the accuracy of MCU ADC can be very high when there is an external reference. However, it cannot reach the accuracy of external ADC chips. (Except for TI battery-powered, I have not tried other MCUs and do not know). The domestically produced ones I have tested are all lax. Especially the MCUs of a certain sugar and xSTC are directly a disaster.

wangerxian

If the requirements are really high, use an external ADC chip. To be honest, the ones built into the microcontroller are not very good.

baopodao

The 0V routing is also important.

QWE4562009

damiaa posted on 2022-10-13 17:09 This is mainly to consider the ripple. If the external interference is large, EMC should also be considered.

How to get the voltage accurate?

QWE4562009

dcexpert posted on 2022-10-13 17:29 ADC cannot rely on VCC for high precision, and requires an independent reference.

It uses an internal reference. Do you want to use a 431? There is no space at all. Even a capacitor cannot be squeezed in.

QWE4562009

dql2016 posted on 2022-10-13 20:44 Use low ripple LDO

What do you recommend?

QWE4562009

wangerxian posted on 2022-10-14 11:50 If the requirements are really high, use an external ADC chip. To be honest, the ones that come with the microcontroller are not very good.

The key is that the board size is limited and a resistor can't be squeezed in.

QWE4562009

baopodao posted on 2022-10-14 14:01 0V routing is also very important.

What's your plan besides copper?

QWE4562009

Qintianqintian0303 posted on 2022-10-13 21:30 The ripple of LDO is generally not large. One way is to use an independent reference. In terms of power supply, the LDO can only be connected without other devices with large power requirements

The LDO current is small, so it is impossible to attach a large load behind it.

wangerxian

QWE4562009 posted on 2022-10-14 16:15 The key is that the board size is limited and even a resistor can't be squeezed in

Are you making a wearable device? If the hardware is really difficult to solve, you can consider using software filtering to solve it.

dcexpert

QWE4562009 posted on 2022-10-14 16:14 It uses an internal reference. Do you want to use a 431? There is no space at all. Even a capacitor cannot be squeezed in.

Internal references are generally less accurate

dql2016

QWE4562009 posted on 2022-10-14 16:15 What do you recommend

ADP150 from ADI has only a few uV ripple

秦天qintian0303

QWE4562009 posted on 2022-10-14 16:17 The current of LDO is small, and it is impossible to connect a large load behind it

This large load is relative. For example, if the output of LDO is 150mA, the microcontroller needs about 40mA. At this time, the load behind it cannot exceed 110mA, which is the peak value.

吾妻思萌

Use a larger capacitor