I observed with our Qi Transmitter and the BQ51221 on the Qi Receiver side a much more stable charging process
if I pull-down the CM_ILIM pin on the BQ51221 with the internal pull-down of the BQ51221. Much more stable charging
process means that the charging doesn't stop in an unexpected manner (or with other words Qi Transmitter keeps
connection with BQ51221). Now my questions.
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In the BQ51221 datasheet it is mentioned that the charger IC which is connected to the BQ51221 output
needs a VIN-DPM feature. In our case we have the charger IC BQ24166 which has a on Pin 1 the input
named VDPM. I assume that the BQ24166 VDPM input fulfills the needed VIN-DPM feature which is
mentioned in the BQ51221 datasheet?
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The BQ51221 output is adjusted in our case to 5 Volt. The voltage divider of the BQ24166 VDPM input
which is connected to the BQ51221 5Volt output is dimensioned in a way that the 1.2Volt threshold of the
VDPM input is reached if the BQ51221 output voltage decreases from 5Volt down to 4.4Volt. Now my
question: Is there any further information regarding the needed VIN-DPM feature and how to dimension
the voltage divider on the VDPM input of the BQ24166 in the right way? I’m asking this to avoid that the
output of the BQ51221 will collapse if the communication current limit is enabled.
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Will the BQ51221 EMC behavior (radiated emission and immunity) change if the communication current
limit is enabled compared to the case of disabled communication current limit?
I would appreciate it to get feedback.