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Original question:

PCA9306DCTR - Wave soldering ( Flow soldering ) profile

PCA9306: Resistance selection

Liu Yang
Expert 8745 points
Part Number: PCA9306

Hi Team,

As for the datasheet "8.1.2 correct device set up", there are setup examples that connect EN and Vref2 terminals to Vcc2 via 200kΩ resistor, but is there a tolerance range of the 200kΩ? (e.g. recommended for use between 180kΩ and 220kΩ etc.)

In the datasheet setup example, Vcc1 = +1.8V, Vcc2 = +3.3 V, while we use Vcc1 = +3.3V, Vcc2 = +5V condition, do you have the optimum resistance value condition under the conditions of +3.3V and +5V? (voltage gap in setup example is 1.5V(3.3V-1.8V), voltage gap in our condition is 1.7V(5V-3.3V). I think there is no difference between 1.5V and 1.7 V)


Beat Regards,
Tom Liu

  • +1
    Guru 316690 points

    The resistor limits the current flowing into V_REF1 and out of V_REF2. The voltage between these two pins can vary, so the current varies, too.

    A minimum current is needed to properly regulate the EN voltage, but the resistor is sized so that it works correctly even with a 1 V difference, so in your case, increasing it to 220 kΩ ± 10 % will work fine. Using a smaller resistor will work as long as V_REF1 can sink the resulting current, but just wastes power.

  • 0 in reply to Clemens Ladisch
    TI__Guru 72731 points

    Thanks for your response Clemens.

    Tom, if you have any follow up questions, please let us know.

    -Bobby