Hello there! I am making a small clock project. It being a simple little project, plus the fact I have completed 4 very similar ones, I decided to skip prototyping and design and etch my PCB right away. It is all good, until I start the MCP1640 regulator.
I am using a version that connects input to output when disabled (Vin=Vout). My plan is to disable everything and go to sleep mode, then, once woken up, turn on the regulator to get voltage to power leds directly from my micro (attiny84). However, once I turn it on, the voltage boosts up to 7, or even 8 volts. Everything else is disconnected apart from Arduino, which I use only to supply power (Vcc, GND connected, no other wires).
The setting resistors are pretty close to the recommended setup. 910k and 330k against recommended 976 and 309. In the datasheet it says that the highest output voltage is 5 volts. I have quadruple checked all connections, if it's not the wrong way around, etc. Continuity tests ok, capacitors are there, the inductor seems fine, plus I have used the exact one before and it worked just fine.
I have tripped over my oscilloscope a while back and tore the probe in half-this and the fact I have other devices with max ratings way below the 8 volts prohibit me from probing around in the circuit.
Any ideas what might be wrong? :(