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PF1550 VBUS_LIN_ILIM resetting

Question asked by Ben Foose on Nov 7, 2019
Latest reply on Nov 13, 2019 by Ben Foose

During brownout testing of a PF1550 design, it was observed that the VBUS_LIN_ILIM setting was resetting to the default value (0x68 400mA) after it was previously set to the desired value of (0xA0 1500mA).


When VBUS falls below 4.2V, the VBUS_LIN_ILIM register value is reset.  No other registers appeared to be effected by this transition.   The documentation in section 8.8.3 of the RM may help to explain this, but it is not clear that the user would need to re-set the ILIM to the desired level afterwards.   Is this the intended operation?


The input-voltage regulation loop automatically reduces the input current limit in order to

keep the input voltage at VVBUS_DPM_REG. Once VBUS drops to the 4.5 V threshold (this

threshold itself is selectable via the VBUS_DPM_REG[2:0] bits), the charging current

is scaled back and this brings back the VBUS voltage higher.