BQ24133: Charge current setting

Dear Jason,

Yes you can set the charge current to 400 mA.

The key here is that the ISET pin has to be biased above 120 mV to be enabled. In the datasheet for example on page 16, the fast charge current must be above 600 mA for a 10 mOhm sense resistor to meet this 120 mV ISET voltage requirement.

If you use a 40 mOhm sense resistor, equation 1 in Section 9.3.2 gives a VISET of 0.32 V. This is above the 120 mV requirement and below the 0.5 V threshold. You would then need a voltage divider from 3.3 V (VREF) to ground that has a voltage of 0.32 V at the midpoint. One such calculation gives the upper resistor to be 100 kOhm and the lower resistor to be 10.74 kOhm.

However, if you want to tweak this design or use different values, I would recommend looking on the Product Page for bq24133, then navigate to "Technical Documentation," and then look for "bqSwitcherII calculation tools." This allows the user to input their desired specs and see the needed components to achieve the design specifications. I have attached the link to the Technical Documentation page below.

https://www.ti.com/product/BQ24133/technicaldocuments

Thanks,

Mike Emanuel

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