Attached is the schematic of my part configured for low voltage mode.
Very close to page 62 in the nRF51822 product specification document.
I am externally feeding 1.8V to the nRF_VDD18 rail. (the 1.8V rail is clean)
I am using a J-link ARM to try program the device. It works fine on all the eval boards as well as custom boards using the built in LDO with 3.3V. The other 3.3V LDO circuit I have all the same parts except the power supply is different, and works fine.
The issue I have is that I can't read or write to the device over JTAG. I get some commands over the jtag to go, but all the read writes to the flash are failing. I have 4 boards built, all with the same issue. I've even swapped to the first generation part, and same problems.
Is there something I missed to run the device in low voltage mode. Did I mis-wire something.
Does Anyone else here have it working running directly from 1.8V without using the built-in DC/DC?
NOTE: If I disconnect my 1.8V supply and drive it from an external 1.8V supply it also fails. If I drive it externally at 1.95V is also still fails. If I drive it externally at 2.0V (exceeding the spec) Then I can get it to program correctly. (I must be missing something)
NOTE2: Even after I can load the code at 2V. the part seems to run correctly at 2V. anything under that, and the part doesn't even run. So it seems that it is more than the ability to program the part at under 2V, the whole chip is not even operating under 2V.
