DAC Usage on CYBLE Series MCUs

[user_1528391]

Hi,

We are planning to use CYBLE-012011 on on of our future products. The board will need BLE connection, ADC readings and also DAC outputs. I see that CYBLE-012011 has 2 current DACs but I have not used IDAC before.

In the datasheet, it says that IDAC can output up to 612uA current. We need an analog output between 0V to 10V for one of our analog ICs. Can we just connect a 20k Ohm resistor from IDAC pin to ground in order to get a 12V output (612uA X 20kohm = 12,240Volts)?

I don't have much experience on DACs, can these IDAC pins work without harming the internal circuits when there is 12V between this pin and ground? Normally absolute maximum value is 3.8V (VDD +0.5) for GPIO pins. But there will be 12V at this pin if we connect a resistor from this pin to ground and give the maximum current output (612uA).

Regards,

Abdullah.

[Vasanth · Accepted solution]

Hi Abdullah,

It is not possible. Even though IDAC can support 612uA, it is within the operation range of the IDAC. Normally IDACs or any devices which is made up of current mirror circuits need to have all the transistors inside it be in saturation for the device to work as expected. The compliance range for the IDAC in the device you are using is from 0.8 V - (VDD-0.8)V. So the range is actually lesser than the absolute device maximum of VDD-0.5V. So if you try to connect such a resistor the voltage will be well within the device working range. If you want to have higher voltage, you may have to use external components and circuits for that purpose. I hope this answers your question.

Best Regards,
Vasanth