Toggling between NT3H2111W0FHKH lowest power and active state

[kriswiner]

I am connecting the NT3H2111W0FHKH to a 32-bit MCU via I2C in a device powered by a small battery. I intend to use the FD pin as a NFC field detect interrupt to the MCU. Unless the NFC field is present, the NT3H2111W0FHKH needs to be in its lowest power state, ideally drawing ~few uA.

However, the data sheet says that when the I2C bus is idle, the device draws 195 uA at 3V3. This is impossibly high for our power budget.

We have thought that using an MCU GPIO to power on and off the NT3H2111W0FHKH VCC might work, to essentially crowbar the device off until an FD interrupt occurs. The other possibility is to use a dedicated I2C bus and disable this on the MCU side when no NFC is present.

What is the best way to keep the power usage to a minimum when the NT3H2111W0FHKH is "idle" and no NFC field is present?

[KellyLi]

Hello @kriswiner 

For your application scenario, it is recommended that you could know the energy harvesting mode of NTAG I2C plus.  The below design could be helpful to you.

BR

kelly

[kriswiner]

So you mean take the power for the NFC IC directly from the NFC IC such that it is powered on only when an NFC field is present and otherwise not? In other words, the NFC field powers VOUT which powers VCC?

This could work.

However, in our application, we would like to be able to write configuration (et al) data to the NFC IC EEPROM even when the NFC field is not present. I suppose we could buffer this data on the host MCU and complete any transactions while the field is present.

But it also sounds like we could simply instead control NFC IC VCC by a host MCU GPIO. Wouldn't this be more or less equivalent to what you are suggesting above?

[KellyLi · Accepted solution]

Hello @kriswiner 

As long as your GPIO port has enough driving power, I think you can try it.

BR

Kelly