Powering from LPC1769 to LM331 an ADC

Thread Starter

jrag6869

Joined May 20, 2019
11
Hi team,

I have to make a project based on LM331 (F-to-V converter) and the microcontroller LPC1769.

From the 5V - USB pin of the micro I have to power all the electronics devices:
-LM331 to 5V or 4.5V
-I have to choose an ADC and power it to the convenient voltage.
- I have to choose an EEPROM and power it to the convenient voltage.

As I know, the USB output from a common PC offers a voltage from 4.4 to 5.25, so I was thinking in a Buck/Boost converter but I'm afraid of the noise.

Do you think it's a good idea to use a LDO (after the Buck/Boost) to power the ADC? The noise from the DC-DC converter will be critical for some part of the circuit? Any suggestion for a good Buck/Boost converter?

Thank you.
 

Zaishens

Joined May 20, 2019
28
Hi jrag,

A linear regulator (LM3940) is a good choice for anything that does not require a lot of power and without huge energy restrictions (small batteries).
I don't understand why you want to put the LDO in series with the buck-boost.

If you need more power or have energy restrictions, a switched mode power supply can be used, in your case a buck converter, I don't think you need to boost the voltage. Then a TL2575 with an Output Ripple Filter will do nicely.

Does this help?

Best regards,
Zaishens
 

Thread Starter

jrag6869

Joined May 20, 2019
11
Hi jrag,

A linear regulator (LM3940) is a good choice for anything that does not require a lot of power and without huge energy restrictions (small batteries).
I don't understand why you want to put the LDO in series with the buck-boost.

If you need more power or have energy restrictions, a switched mode power supply can be used, in your case a buck converter, I don't think you need to boost the voltage. Then a TL2575 with an Output Ripple Filter will do nicely.

Does this help?

Best regards,
Zaishens
It's a good idea to use the ripple filter, but I was thinking in a buck/boost converter because I need 5V for the LM331 and the USB input range is from 4.4V to 5.25V (Please correct me if I'm wrong)

In that case, I can use the buck/boost converter to supply the LM331 and the LDO to supply the other components. Or can I supply all the circuit with the buck/boost converter? I'm asking that because as I said, I'm afraid of the noise from the buck/ boost.

Best regards,

John
 

Zaishens

Joined May 20, 2019
28
You can power the LM331 directly with the USB power (Vs = 4-40V) no converter needed.
Only the ADC needs a more known and stable voltage, hence the LM3940 linear regulator.

That is, if you don't have the energy restriction, otherwise use the TL2575 with an Output Ripple Filter
 
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