BQ25505: 160uA power consumption when no solar panel

Francois,

Just to confirm, you are seeing 160 uA from the battery to BQ25505? If this is the case, what is your /VB_SEC_ON signal and you VIN_DC voltage when you are seeing the current draw? Would it be possible for you to recreate this on the EVM?

Thanks,

Ricardo

yes I see 160 uA from the battery to BQ25505.

VB_sec_on = 0v

vin_dc =~ 0.1v

I not able to do this test on EVM.

Francois,

I suspect that either VBAT_SEC is charging up VSTOR or there is a short of some kind from VBAT_SEC to GND.

The former is true when VSTOR is less than 100 mV and a partially charged battery is applied to VBAT_SEC. This however occurs pretty quickly (50 ms) and I do not suspect it to be your concern.

The latter is would an external short from VBAT_SEC (pin 18) to either NC to GND (pin 17) or VSTOR (pin19). This short could be solder or even flux residue. Are you seeing the 160 uA leakage exclusively on this board? Would be possible for you to remove the IC and resolder a new IC? Before trying the new IC be sure to clean the board thoroughly with flux remover spray.

Thanks,

RIcardo 

Hi Ricardo,

I try to clean with solvant the solar section with no sucess.

but before to do other things like change the IC, i have some question about the internal BQ25505 circuitry.

how much current take BQ25505 on the VBAT_SEC pin when we have no input on VIN_DC and LBOOST pin?

i attach our schematic.

i make sume other test and i find the current draw by the BQ is in relation with the VBAT_SEC voltage. 160uA with VBAT_SEC = 4.19V and less current if VBAT_SEC have less voltage.

And when the VBAT_OK pin are 0 we have no current draw by the BQ.

thanks

BQ25505 section.pdf

Henrique,

Upon startup VBAT_SEC will charge up VSTOR and that will cause a brief peak current according to i_C = C(dV/dt). On the EVM I am observing observing a rise time of 79.6us to go from 0 to 4.19V with the VSTOR capacitance of 4.7uF + 0.1uF. This would result in an i_C of ~250mA for those 79.6us. After charging, the device is in a steady state drawing less than 1uA from the battery.

You say you are seeing 160uA consistently, so I still believe there may be current leakage or the device may be damaged. I am interested as to why you are inverting the /VB_SEC_ON signal using an NPN to drive the VB_PRI PFETs and vice versa. 

I was not able to recreate what you are seeing on the EVM. Would it be possible for you to make the modifications I have marked on your schematic to more closely match the EVM?

Thanks,

Ricardo

Scanned from a Followme printer-rotated.pdf

We cannot remove transistor Q29, Q35 from our schematic to isolate the voltage From VBAT_SEC (4.2v) and VBAT_PRI (6.5v).

We invert logic just because we use 2N3904.

We cannot remove transistor Q29, Q35 from our schematic to isolate the voltage From VBAT_SEC (4.2v) and VBAT_PRI (6.5v).

We invert logic just because we use 2N3904.

Henrique,

I suspect somewhere in this extra hardware there may be leaking current or that the IC is damaged in some way. Unfortunately your design is so different from the datasheet and the EVM that I am unable to diagnose the leakage current further on my end. Have you had any luck swapping the IC?

Thanks,

Ricardo

no, swapping change nothing.

iam continue to work on the issue and if i have another things, i make another ticket.

you can close this ticket.

thanks,