Other Parts Discussed in Thread: BQ25756, , BQ25756E
Tool/software:
Hello TI,
I'm using the TPS25751 with a BQ25756 and i'm trying to supply the power to a cellphone (9V PDO), i would require your wisdom to know if i'm missing a setting or error that would lead to this issue.
CAN DO :
I have no issues supplying 5V to the cellphone, 5V from the BQ charger (supplied from PP3)
I am also supplying another device (USB PD devkit board) at 20V and i can supply 3A no issues
CANT DO :
For the 9V to the cellphone, it is not working and i wonder if you have an idea of what is going wrong and if a advanced parameters could help.
Here are the waveforms of the activity on the USB voltage lines.
BQ charger has PFM mode enabled by default and i think maybe the ripple is to high (there should be an update of the USB config tool to allow us to disable this feature)
Also i would like to test increasing reverse current protection or slew rate parameters, not sure where i can set those.
Here are three scenarios' results : 5V source through PP3, 9V source (preffered role = source) and 9V source (preffered role = sink)
5V_PP3 successful negociation :
Blue : Charger output voltage
Green : USB Voltage
Red : Battery current
5V is generated by the charger -> 5V appears on the USB VBUS -> Charger voltage is connected to the USB VBUS
9V sequence (preffered role = sink)
Blue : USB Voltage
Green : Charger output voltage
Red : Battery current
Yellow : Low side switch gate
9V is applied to USB Vbus but charger is asked to stop and phone starts sending 5V instead to charge my device. (i would like to charge the phone)
9V sequence (preffered role = source)
Blue : USB Voltage
Green : Charger output voltage
Red : Battery current
USB PD request charger for 9V but does not allow it through to the USB VBUS
