# Stamp pico min max V

• Hi all. Can anybody tell me which is the minimum and the maximum allowed voltage for Pico Stamp? I see it has a 5V DC DC so I was wondering if it can accept a lower voltage.

I’m designing the electric circuit in my new house and I was thinking to have cables with either 5v or 12v in every room wherever I will need an ESP32. So I was calculating the necessary cable diameter for 5V @ 500mA and the relative accepted voltage drop (cables will be up to 10-13mt long).

Thank you.

• Hello @zahari4i

have looked at the schematic?

Thanks
Felix

• the ESP32 runs on 3v3 but the stamp modules uses 5V input
The 3v3 pin used by the programmer pin can be used to provide a 3v3 input but sometimes I have found the stamp will crash.

• @felmue hi yes, not very good at reading schematics but I wasn’t able to find anything else other than the fact it needs 5v 500 mA. Am I missing something?

• @ajb2k3 what about feeding it lower voltage at 5V. I read it has a DC DC incorporated so I was wondering what tolerance it has. Depending on the distance I will sometimes have 5, 4.9,4.6 volts. The lowest I’ll go as per my calculations is 4.6V.
Do you think this would be enough to safely power the stamp?

• Hello @zahari4i

well, on the schematic you'll find the DC-DC converter (SY8079AAAC) - its datasheet should help you getting the info you're looking for.

Thanks
Felix

• @zahari4i Sorry, my bench supply isn't working yet and so I get test to see how low the stamp will go.

• @felmue thanks a lot. From the datasheet I see a range of 2.7 to 6.5V. So basically I have no problems going even lower than 4 volts. That’s great news! Thank you!

• @ajb2k3 some empirical evidence would be great, whenever you have time to check it. Thank you

• Hello @zahari4i

please keep in mind that the used IC only is a step-down DC-DC converter. This means the input voltage needs to be above the output voltage. By how much I couldn't figure out from the datasheet though. I'd suspect something like 0.6 V. So for an output voltage of 3.3 V you probably need at least 3.9 V input voltage. If you go lower the output voltage will go lower as well.

Also keep in mind that the ESP32 have a rather high peek current, especially when doing WiFi stuff. I'd plan on adding some capacitor close to each device to cover for that.

Thanks
Felix

• @felmue if the margin above 3.3V is somehow related to the Feedback Reference Voltage than the datasheet confirms it’s 0.6V. That should be no problem as I think I’ll stay above 4.5V. Regarding the capacitor thanks for the hint, I’ll keep in mind that. I’m somehow limited in space but I believe it would be no problem finding something small to be connected on the cables just before the Stamp. Thanks again for the inputs.

• 工作电压/供电电压 3.0 V ~ 3.6 V
Operating voltage/supply voltage 3.0 V ~ 3.6 V