BQ24193: Design Validation

Hi Srini,

First on your questions, if the device in powered by VBUS, and there is no battery load the device will regulate VSYS to the VREG voltage. With a battery it will depend on the battery voltage and some of the settings in your registers. In constant current mode the charger will continuously alter VSYS to achieve the set charger current. You can however set a VSYS_MIN (default 3.5V) when voltage needed to achieve the set charge current is bellow this value, the BATFET will act as a Linear regulator to ensure a controlled charge current while keeping the SYS voltage above VSYS_MIN.

For OTG configuration do you mean hardware or register settings?

The load current is not dependent on input voltage.

Schematic Review

1. the 22uF of Capacitance on VBUS is likely more than what is actually needed. 1uF is recommended.
2. they may be included in another schematic but pullup resistors are needed for pins 3-7
3. Note that for the ILIM pin the actual current limit will be set by the lower of what is set by the resistor and what is set by the registers so make sure to set your registers properly.
4. I see it is indicated as NP but the diode on BTST is not needed
5. I see that the bias resistors for the thermistor are set the values from the Datasheet, please not that those values are specifically for use with the 103-AT thermistor, if you are using a different thermistor you may have to change this.

Lastly I am not sure what the loads of you device are or the EMC requirements but sometimes placing a ferrite bead on a power rail for digital loads can do more harm than good in terms of EMC. This article may be helpful.

https://resources.altium.com/p/how-use-ferrite-bead-your-design-reduce-emi