Other Parts Discussed in Thread: UNIFLASH,
Hi,
I have designed a PCB that used the IWR6843 and am having difficulties programming the flash using UniFlash.
About the PCB. This is the second revision, which is practically identical except for minor adjustments in the power supply circuit (additional bulk capacitance + layout changes). The first revision was very successful and could be programmed as outlined in the documentation.
SOP0 is shorted to 3V3
SOP1 is shorted to GND
SOP2 is connected directly to a header that is controlled by a microcontroller. All of the following observations are when the IWR6843 is disconnected from the microcontroller, the SOP2 like rises to ~3.15V.
When I short SOP2 to ground, a significant amount of current is drawn (~150mA) from the 3V3 rail which is the limit of the LDO that supplies the IWR6843 and this causes damage to the IWR6843 (All subsequent power supplied to the 3V3 rail is essentially short circuited to GND, all other voltage rails operate as intended).
The SOP2 can be pulled high to 3V3 without any additional current consumption.
Using a 1Kohm resistor I was able to pull the SOP2 line to near GND (~0.1-0.2V), but this didn't change the operation, or capacity to program the device.
This issue is across several PCBs, all of which were professionally made.
I have swapped the IWR6843 chip on a single board with a IWR6843 from the same batch as what was loaded on the PCBs.
The current consumption of this PCB is similar to the previous revision drawing ~20mA in reset, and 130-145mA in idle/Programming.
Based on the documentation the SOP2 line at reset should Input, at reset it should be output disable, and it should have a pull down resistor. These are all the opposite of what I have found.
I removed the 3V3 supply to the IWR6843, and then SOP2 was GND. After resetting the IWR6843 (while there was no 3V3 supply) the SOP2 was pulled up to approximately 1.2V.
I also tried to contact the IWR6843 using the UART interface with SOP state (101 and 100). I sent the PING command (0xAA, 0x00, 0x03, 0x20, 0x20) and received it as an echo (same bytes delayed by one byte).
All voltage rails look stable. Flash chip is a MX25V1635FZNI.
Thanks in advance
Matthew
