SLUSDF9 June 2020 BQ25790
At POR, before the charger converter starts switching, the charger ADC reads the ILIM_HIZ pin voltage, and calculates the input current limit (ILIM) set by this ILIM_HIZ pin, according to the equation VILIM_HIZ = 1V + 800 mΩ × ILIM. The ILIM_HIZ pin sets a high clamp for the IINDPM register. If the IINDPM setting from the D+/D- detection or the POR default 3A IINDPM setting is higher than the ILIM clamp, the IINDPM register stays at this ILIM clamp. In addition, the host cannot program the IINDPM register to any values higher than this ILIM clamp after POR, unless the register bit EN_EXTILIM is set to 0.
The ILIM_HIZ pin can be biased from an resistor voltage divider that can be tied to either the REGN or the other external voltage source. For both the forward charging mode and the OTG mode, when the ILIM_HIZ pin is pulled lower than 0.75V, the charger stops switching and REGN stays on. The charger resumes switching if the ILIM_HIZ pin voltage becomes higher than 1V.
If the ADC reads the ILIM_HIZ pin voltage is lower than 1.08V (1V + 800 mΩ × 100 mA), the charger considers the ILIM clamp to be 100mA, which is the minimal setting of the IINDPM register.