GPIO sink current on nrf52832

The table on:

infocenter.nordicsemi.com/.../gpio.html

specifies: Iol,hdh = max 15 mA for Vdd >= 2.7V.

The graph lower on the page (Figure 6. Max sink current vs Voltage, high drive) specifies around 22 mA for Vdd = 2.7V.

Which one is correct, or what's the difference between the two?

I want to drive a RGB LED using the low power pwm lib. Each of the LEDs needs max 10 mA.

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  • This is discussed in this thread.

    To summarize:

    We recommend 15mA total current sink/source on the chip for normal operation. This can be on one pin if you want (different than nRF51). We recommend that you sink current rather than source current because of more ground pads than vdd pads.

    UPDATE 2016.08.18:

    Iol,HDH is described as

    Current at VSS+0.4 V, output set low, high drive, VDD >= 2.7 V

    And is typically 10mA. If you put it the other way around you can say that typically if you sink 10mA on the pin, the pad voltage will rise to VSS+0.4V. This corresponds to Figure 4. GPIO drive strength vs Voltage, high drive, VDD = 3.0 V.

    The maximum current you can sink in high drive if Vdd is 3V is 25mA from figure 6. But if we take a look at figure 4 again we see that the pad voltage is then 3V, which means that you will have problem driving an LED with 25mA.

    The reason you should not sink 15mA on multiple pins is that some pins may have common ground path. This means that if you sink high currents on pins that are close to each other you may see that the voltage on both pins (pads) rise above what is specified in Figure 4.

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