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PCA9306: EN pull up resistor

Praveen GD
Guru 57737 points

Part Number: PCA9306

Hi,

This is regarding the Pullup resistor connected between EN pin and supply. From datasheet, I understand that  the gate of the transistors is controlled by the voltage on the EN pin. There is no mention on the Current flowing into the EN Pin.

In datasheet, Figure 7. the value of this resistance is 200k Ohms. Is there any min and max limit for the resistance that can be used ? If so please provide the range.

Thanks,

Praveen

  • 0
    TI__Guru* 78111 points

    Hey Praveen,

    Here is how the Vref1, Vref2, EN pin, and 200k ohm resistor are related to each other:

    You can see here that the 200k resistor is used to limit the current between Vref1 and Vref2. Current does not continuously flow into the Enable side because it is a gate of a FET which is seen as high impedance. If you choose to lower the resistance, all you will see is more current consumption and increased power dissipation. The minor advantages will be the device will turn on and off slightly quicker (imagine an RC where C is parasitic capacitance on gate).

    ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    The minimum resistance would be the:

    Absolute Max current: 128mA

    Rmin=(Vref2-Vref1-Vth)/Imax

    Where Vref2>Vref1+0.7V for current to flow.

    -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    I'm not sure if there is a Maximum resistance but if you make your resistance extremely large then the thermal noise of the resistor will increase and affect the reference voltage established.

    Thanks,

    -Bobby