I have a board with ADM8611N263ACBZ-R7, I got intermittent correct reset. when I measured the resistance between Pin A1 and C1, I got something around 5Meg Ohm, can I assume that either A1 or C1 had a bad solder point.
R48 is not loaded. V_BAT is 3.8V, both MP_POR and BT_POR are low. but I only see RESET_N been pulled high intermittently. is it because the internal pull high resistor too weak in this case. should I put I 1M resistor at R48. thanks
I don't think you need put a resistor at R48. please check the circuit of Q1A and Q1B especially the FET gate singal.
Thank you very much for replying my question. now for the same design I have one more question, as in the schematic in Feb 9th, we have built 8 boards, there is only one board behaved a little strange, I measured V_BAT is 3.826. TP12(input to MR bar) is 3.5V. LDO_EN(Reset bar output) is 0.020V.
so the chip must put itself in reset mode. to analysis why this happen, only one assumption make sense to me.
that is the VCC pin ( U3.A1) is floating( not soldered solid on the board). the voltage coupled to the VCC from U3.C1 or U3.C2 which is 3.8V. and U3.A1 see this coupled voltage lower than 2.6V low voltage threshold. so it stuck at the reset status.
Is it possible that the voltage from pin U3.C1 or U3.C2 which is 3.8V can couple back to the VCC pin? what is likely the voltage if this could happen?
I don't think /RESET or /MR can couple back to VCC. Can you confirm if the R48 is soldered on the board or not?
Also, according to your description above. Most likely, it is the U3 soldering issue. Can you re-solder the U3 and make sure the soldering is good, then test again? thanks!