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BQ25570: charger efficiency at low and high lux values differ

Part Number: BQ25570

In BQ25570 how is VREF_SAMP and VOC_SAMP are related. Is the VREF_SAMP = VMPP?

In the ckt, we have set Roc1=10M+4M=14M, Roc2=6M. and our panel Voc=4.57V.

Is the resistor settings correct? what should be the VMPP to be set? 

  • Hi Godwin,

    VOC_SAMP is the input pin for the resistor divider that senses the input source's open circuit voltage.  The pin is the input to a sample and hold circuit.  The output to the sample and hold circuit is capacitor on VREF_SAMP.  The capacitor on VREF_SAMP must have very low leakage (have insulation resistance so needs to have a high voltage rating) and can't have a resistance on it (like a scope probe with 10Mohm resistance) or it will discharge too quickly.

    Using https://www.ti.com/lit/zip/sluc461, I compute the same values for the Rocx resistors, assuming MPP = 0.8*4.57V = 3.656V.  I recommend reviewin datasheet section 10.1 regarding parasitic resistors formed by residual solder flux.

    Regards,

    Jeff