BQ25890H: proper cable selection

Eric,

The bq25890H does not fully interface with USB PD connectors. You will likely need an interface chip for full compability with USB PD. The bq25890H is designed to operate with USB BC 1.2 specification, which includes USB 2.0/3.0 ports as well as 5V DCP (non USB) adapters up to 3.25A output. In addition, because the host I2C can write to the charger's I2C registers that control the voltage levels of the D+/D- lines, this charger can interface with certain other High Voltage DCP (HVDCP) adapters, telling them to raise their output voltage from 5V to 9V or 12V, thereby reducing input current. You can get more detail at www.ti.com/.../slua786.

That said, you can control the input current to the charger via an external resistor on the ILIM pin or I2C registers (called INDPM). In addition, you can set a VBUS voltage threshold below which the charger will not let VBUS fall (called VINDPM). As if that wasn't enough to prevent adapter collapse, this charge has an ICO feature which will automatically roll back the input current to prevent hitting VINDPM. More info on that feature at www.ti.com/.../slva812.

Most customers choose a cable with resistance that will not allow the input voltage to the charger to droop below the VINDPM threshold at maximum adapter current. The VINDPM threshold should be set high enough to prevent the charger's buck converter from entering max duty cycle. You can compute this recommend value from equation 5 of www.ti.com/.../slyt569.pdf and the charger's FET resistances from the bq25890H datasheet.