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I am trying to control the current to a Raspberry Pi using a MOSFET and an ATtiny10. I am using a logic level MOSFET and it seems that the Pi needs about 250mA to turn on but it is only able to pull 120mA. My power source is 5V 3A. I have the circuit below. Any idea why I am unable to pull enough current to turn on?

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NOTE: The answers below about breadboard causing Voltage and Current drops and the Pi rebooting due to over current draw are equally helpful. I accepted the answer that matched the Title question most.

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    \$\begingroup\$ Note that this is a follow-up to a previous question. The OP has changed to a different MOSFET (per recommendations) that should work. @SChand, please measure the gate and drain voltages. With a meter and scope if possible, just in case something is oscillating. \$\endgroup\$ – Mattman944 May 15 at 22:51
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    \$\begingroup\$ What are the voltages across the MOSFET's Gate to Source and Drain to Source when it is turned on? \$\endgroup\$ – Bruce Abbott May 15 at 22:53
  • \$\begingroup\$ @Mattman944 it is roughly 4.1-4.5V... I am seeing that the current supplied as well as the voltage is not very stable. The current goes 60mA, 90mA, 120mA, 200mA and then resets from 60mA. Not exactly those numbers but the current is not stable \$\endgroup\$ – SChand May 15 at 23:53
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    \$\begingroup\$ It looks like the same breadboard that I had issues with recently. I was astonished at the voltage drops I saw at 1/2 amp. You need to solder the circuit. \$\endgroup\$ – Mattman944 May 16 at 1:37
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    \$\begingroup\$ I also have a breadboard that looks like that. It's horrible. 4.5V on both Gate and Drain at the same time suggests a poor connection from Ground to Source. Did you measure directly across the MOSFET leads, or to another place on the board? \$\endgroup\$ – Bruce Abbott May 16 at 5:19
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Cheap solderless breadboards are not adequate for circuits that draw several amps. The resistance between contacts can be as high as 1 ohm. At 2 amps (most RPi's will draw at least this much), a few volts drop can cause serious issues. A 2V drop in the MOSFET source path will cause the gate-source voltage to be 2V less than expected.

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  • \$\begingroup\$ Thanks! I switched all components to a soldered board and have stable V and I throughout now. Definitely will be investing in a more reliable test board now. \$\endgroup\$ – SChand May 16 at 22:32
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Here's a low side switch with a 250 mA load current and a 2.5A active current limiter . If you disable the current limiter the supply current spikes up to 17A in this simulation.

Theory

Unknown Pi load capacitance causes low side switched supply to shut down from over current causing it to cycle on-off.

Soft start solution

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Here is what I think the problem is.
(Ignore transistor which is bypassed now and current spike is 17A) enter image description here

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