Original question:
Tool/software:
we are seeing similar issue to this where we are getting 15 pulse during startup but there is no output.
In Our Design, FB_B3 and FB_B4 are open somehow, is there any workaround to get PMIC to work either reconfiguring it from scalable-pmic-gui.
Hi Punit,
Per TPS65931211 User-guide (https://www.ti.com/lit/ug/slvucm3/slvucm3.pdf) FB_B3 must be connected to 3.3V voltage which is available and valid before 10ms is elapsed from GPIO4 set high.
I would recommend starting by connecting FB_B3 to VCCA supply to see if that solves power-up issues. And compare schematics overall to user's guide example.
PMIC configuration can be changed over the I2C interface using GUI. That just means you would need to develop new NVM for this situation FB_B3 is unconnected.
Br, Jari
Hello Punit,
Unfortunately a NVM change can not and will not solve the issue if the schematic posted is what you have system level, the BUCK feed back pins FB_B3 & FB_B4 need to be connected properly as that logic is fixed in it's behavior. These pins need to be connected in order for the BUCK loops to function, these do not function in open loop feedback.
The only solution that can be done is that if you need something up for superficial testing of prototype boards, is to wire up the trace to the output of the inductor for BUCK4_VOUT and the same trace from FB_B3 is connect to the 3V3 IO load switch, this is not a recommendation from TI for a evaluation setup or production.
From that User's Guide that Jari posted, there's a system block diagram that shows the connection he was talking about with the FB_B3, that connection is absolutely necessary.
Here's some comments on the current schematic:
Best Regards,
Nicholas McNamara
