I am using the MIC29300 https://www.microchip.com/wwwproducts/en/MIC29300 in my circuit to generate a 5V signal to my ADC (works fine now)

Would it be possible to grab that 5V line and have it provide the power for my Raspberry Pi 3 Model B+? Would it cause voltage fluctuations and affect my ADC? Should I just use another IC?

  • Ah, I feel jealous that you are using MIC 2930x LDO, which is 10 times more expensive than the cheapie LM2596 I have been using all these years. I know MIC2930x is industrial grade, with the following non LM2596 features: (a) Low dropout voltage, (b) Low ground current, (c) Accurate 1% guaranteed tolerance, (d) Extremely fast transient response, (e) Reverse-battery and load dump protection, (f) Zero-current shutdown mode, (g) Error flag signals output out-of-regulation. – tlfong01 Feb 18 '20 at 2:40
  • References:MIC2930x 5-Lead TO-220 Fixed Voltage High-Current Low Dropout Regulators ww1.microchip.com/downloads/en/DeviceDoc/… – tlfong01 Feb 18 '20 at 2:41
  • The IC you’re using looks good. What about the LTM8063? I imagine that they all function the same. The MICa to give out a ton of heat, which is not the best. However, they provide with a clean circuit which is a big pro, but maybe it’s an overkill for powering the pi. I’ll want to try and use a switching circuit to power on the PI and see if the 5V line from the pi is good enough for my adc to have a stable reference. Although it might have some internal management for that anyway. – George Feb 18 '20 at 10:29
  • Just a quick reply. (1) Switcher regulator such as LM2596 has high efficiency. In other words, if Vin = 12V, Vout = 5V won't lost much power as heat. On the other hand LDO efficieny depends on Vin, If Vin = 6V, then not much heat generated. But if Vin = 24V, then the chip might be very hot. I have tried other switching regulator 10A. 12V etc, they don't heat up much. I don't use LTM8063, because there are no cheap modules around :) – tlfong01 Feb 18 '20 at 10:46
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    I have a US$300 digital scope, so I usually use it to display the waveforms. And I am mostly prototyping, not mass production, so I usually afford time, space, and money to over kill. Sometimes I just show off, eg, that I have a 10,000uF cap, to make my bad friends feel jealous. – tlfong01 Feb 18 '20 at 14:03

You COULD use a linear regulator if you have a large enough heatsink because any linear regulator will dissipate lots of heat.

Whether the voltage would be stable and sufficiently clean depends on the circuitry you put around the regulator.

I wouldn't use a linear regulator switch mode power supplies are preferable.

PS I don't know why you would want to use a separate regulator with an ADC - most have precision internal references, which are temperature stabilised.

  • The ADC I am using is the MAX1204 and requires a 5V power supply. I believe the internals reference is set at 4.096 V (which works great) but I still need to power the device with a 5V line. – George Feb 17 '20 at 23:01
  • Would you recommend this IC: analog.com/media/en/technical-documentation/data-sheets/… ? – George Feb 17 '20 at 23:06
  • What is wrong with the 5V pin on the Pi - that is what the rest of us would use. – Milliways Feb 17 '20 at 23:09
  • I could give it a shot. I was under the impression that the raspberry pi has a noisy environment which is why I didn't want to try and use it's power supplies. The ADC has an internal reference, but I was also under the impression that it depends on how clean the VDD signal is. Garbage in = Garbage out. And I just wanted to show you. Some people like to have the links. – George Feb 17 '20 at 23:19
  • Sorry, I will be more careful next time. – George Feb 17 '20 at 23:24

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