NRF52832 high power consumption on IDLE and 1.556V on VCC

[BartoszT]

I made 20 pieces of porototype devices. Testing some damaged them, NRF52832 does not work and the voltage on them is 1.556V, others work again but after disconnecting the power supply when they remain on the power supply from the supercapacitor (2F) through the resistor (160R), the voltage on them also is 1.556V. I also have those that work properly and then the power consumption is 4uA or slightly more, e.g. 7uA. I would love to understand what is causing this problem which I would call 1.556V on IDLE when BLE is off. I am using an internal DCDC converter. Initially the current consumption is slightly above 2mA and then decreases but the voltage 1.556V is still the same.

[ketiljo]

1.556 V is too low to power the chip, so it will be held in power on reset (POR) until the voltage is high enough, 1.7 V

The 160 ohm series resistor is too high to power the device from the super caps. There will be too much voltage drop across R7 when  the device is operating. When the CPU is running, drawing ~4 mA, the voltage drop is 640 mV and when the radio is operating, it draws an additional 8 mA, causing a 1.9 V voltage drop. This will trigger POR as soon as you start the radio.

BTW, C20 and L3 are mandatory components, see the reference schematic. 

[BartoszT]

this device works correctly with a 160R resistor, but only when the supercapacitor is empty and charging then the phone does not always want to connect via BLE to the device. I will reduce the value of this resistor.

But once again I return to the problem of 1.556V.
Which is the reason that after disconnection of the power supply and power supply by the supercapacitor, the voltage is very stable at 1.556V?  The current flowing out of the supercapacitor decreases but the voltage is constant. Looks like some inverter damage.
In my schematic there is C10 (1uF) and L2 (15nH) in the device it is also mounted.

[ketiljo]

1.556 V is well below the operating voltage of the device. It's being held in POR untill the voltage rises above 1.7 V. With a 160 ohm series resistor, the voltage can't be high enough because the device starts to draw current. So you must remove this resistor. Even 10 ohm is too large and will create too much ripple voltage. 

I guess you have 160 series resistor to slowly charge the supercaps. You can use diodes to control the current flow, like this: 

D6 and D13 are probably not needed.

[ketiljo]

When I think of it, the diode in series with R7 is not needed, so only add the diode from TP9 to TP8. You can also get the voltage to charge the cap between D6 and D7. This way, VDD will always have the same voltage if the regulator or the cap is supplying the device.