I'm having an issue with the ADP5090 startup sequence with some of my PCB's. Some of our PCB's came back not working. I use the ADP5090 to charge and manage a small 25 mAh Lithium polymer battery and use RFID Vout to as Vin for the ADP5090. This works fine on most of the PCB's but some the ADP5090 never achieves a stable SYS voltage as shown in the measurement below:
Note: Voltages are a bit higher than in real life due to max setting on scope.
More zoomed in on the issue. SYS reaches a good voltage but than collapses back to the End of Cold-Start Operation Threshold.
This is the schematic used:
Hope anyone can point me in the right direction of this issue.
the problem should be SETPG and SETSD same or too close. When the PGOOD is high, ADP162 will startup and the SYS and voltage will drop so that the SYS and BAT connection will turn off.…
That should be safe. in factor, you can calculate the rough voltage drop during transist the energy from SYS and BAT to ADP162 output capacitor considering to the peak current of the ADP162…
The ADP162 startup will make this droop. so if you can program a higher Pgood, after the battery connected, the droop should be smaller.
you can montior the BAT voltage with the oscilloscope to get the voltage drop when the PGOOD goes high. it may help to calculate the peak current during the ADP162 startup.
if the battery internal resistance is too big, the BAT will be disconnected as long as the voltage drop is bigger than 140mV you set.