BQ25713B: Charger doesn´t power up from DC-Soure

Hi Andre,

   Can you check if you have tripped the SYS_SHORT fault? You can check the chargestatus register to verify. Please also verify voltage on ILIM_HIz pin.

Hi!

As a supplement, here are the signals of HIDRIVE1 (red curve) and LODRIVE1 (yellow curve) for different voltages at VBUS.

The voltages at ILIM_HIZ-Pin are:

2.6 V @ VBus = 5V

2.9 V @ VBus > 6V

I´ll check the chargestatus register.

Kind Regards, André

Hi Kedar,

thanks for your help! Here is the missing information about the chargestastus register.

It's the same as the eval board and I can't see any unusual.

best regards

Hi Trix,

   The watchdog timer is set for 175 seconds. This needs to be disabled as otherwise it will reset to the default value every 175 seconds, and default value of charge current is 0A, which is a charge disable scenario. You can find this in the ChargeOption0.

Hi Kedar,

I tried what you suggested but it doesn't seem to change anything. :(

Can you confirm that our schematic is correct?

I also checked again with the eval board and used the same register setup but on our board we still got the described behavior.

Do you have any other idea what we can try?

best regards

Hi Trix,

   Are you observing the same behavior on the eval board? Do you have a SYS load? Can you disable the SYS load during converter startup?

Hi Kedar,

it´s not the same behavior on the eval board. As systemload, we have different buck-converters. But we have removed them from board to make shure, these are not causing any problems. We also tried boot up the Eval-Board with any load and this works correctly.

At VBAT, we have an other circuit around BQ40Z80 battery gauge and this part also works correctly with eval board BQ25713EVM-017. We also tried to disconnect the applied circuit at VBAT, but it´s the same behavior of charger circuit.

Is the charger circuit very sensitive to applied layout? Should the Charger-Pins SW1 SW2 connected with a polygon or is a small track enough? 

Finally, we assembled only the charger-part (parts of schematic of origin post) and no other components, and charger shows in Sys-Short fault every time.

From showing Sys-Short-Fault, there is no signal at the gates of switching FETs.

Can there be any other reasons for showing this fault? There is no short at VSYS or VBAT.

Regards, Andre

Hi Andre,

   Converter has a soft start on startup so you should enable load after the converter deglitch time. You can disable SYS_SHORT in ChargeOption0 register. If the fault is detected it has to be cleared manually in ChargeStatusRegister.

As this is a charge controller, layout plays a huge factor. Minimize the copper area of this trace to lower electrical and magnetic field radiation but make the trace wide enough to carry the charging current. Do not use multiple layers in parallel for this connection. Minimize parasitic capacitance from this area to any other trace or plane.

A thin trace will not be able to carry the full charge current, as this is part of the high current carrying path.

Hi Kedar,

is it possibe to get the altium files from BQ25713EVM-017 to compare with our design? - Thanks. 

best regards

Hi Trix,

   Sure. I have sent you a request through E2E to share privately.