Hi,
The circuits is almost the same with TPS4811-Q1 EVM board, I pasted as below:
TPS4811 should turn on MOSFET Q60,Q47 (Q13, Q14 not loaded) when INP signal is high, the testing was set as below:
I input a DC voltage of 48V from P_BAT connector,
I measured Voltage level of INP is about 2.7V, INP_G voltage level is about 2.7V.
After I powered on the DC supply, I supposed the MOSFET should be turned on because INP/INP_G is 2.7V high, but sometimes I found the MOSFETs wasn't turned on, the voltage level of PU/PD is about 39V,sometime the MOSFET was turned on successfully, the voltage level of PU/PD is about 60V. the failure mostly occured on the first time I powered on the DC supply, if I continued to turn off/on DC power supply, I found MOSFET can be turned on.( this phenomenon occured with PRE-CHARGE function enable);
If I disable pre-charge function by pull down the signal of INP_G to low, the other setting and operation is the same with above, the MOSFET was not turned on at all, I captured the signal waveform of PU/PD, it looks as below:
there is a pulse after I powered on the DC supply, then PU/PD goes to low.
Would you advise what I can do to turn on the MOSFET without PRE-CHARGE function enable?
Why MOSFET sometime was failed to turn on even I enable Pre-charge function?
Thanks
Kelvin