NT3H2211 power consumption from I2C side

[michaelklokov]

I'm working on a very-low-power device with number of sensors/ICs on I2C bus and I want to add some functionality to transmit collected events via NFC. NT3H2211 looks quite suitable, but I can't find the answers to several questions:

1. What the supply current of NT3H2211 powered from VCC (1.8Volts) only (with no I2C communications at all)?

2. Will NT3H2211 steal power from I2C bus (via I2C pull-up resistors) if its VCC remains floating and no field present? How much?

3. What the supply current of NT3H2211 powered from VCC (1.8Volts) only (I2C used by other devices on I2C bus, but not NT3H2211)?

The datasheet and googling not really helped, so I look for someone who can directly try and measure these paramefers.

[michaelklokov]

Ok, I've just received this IC and made some measurements.

- The bad thing:

Power consumption is really large even with no communication. (~135uA @ 1.8V; ~160uA @ 2.5V; ~170mA @ 3.3V ).

So you can not power it forever - it will eat up your battery even doing nothing.

- The good thing:

It does not steal power from I2C or FD pins if VCC is disconnected.

So you can connect it constantly to shared I2C bus and FD pull-up and power this IC only when you need it.

Hope it helps.

[IvanRuiz]

Hello,

Please refer to chapter 13.1 Electrical characteristics, table 42. Characteristics for the I2C interface characteristics where the maximum supply current is shown for 1.8 V:

https://www.nxp.com/docs/en/data-sheet/NT3H2111_2211.pdf 

Keep in mind that if NTAG I2C also powers the I2C bus, VOUT must be connected to VCC and pull-up resistors must be sized to control SCL and SDA sink current when they are pulled down.

Regards,

Ivan.

[michaelklokov]

Thank you, Ivan.

I saw this table before.

It describes the values for 400kHz I2C communication. I believe it's a sort of maximum consumption rating for this IC (when it actively receives commands on maximum speed, writes eeprom and so on.)

And you can see that "minimum" and "typical" values are not available.

As you can guess I'm trying to minimize the consumption in idle mode (say, my device wakes up once per hour).

The value from the table you mention looks too large for doing nothing.

Anyway if you have NT3H2211 on you workbench, It would be extremely helpful, If you could measure the VCC consumption with no communication.

In fact you can leave all the other pins (except VCC and GND) floating - it should not be really hard :smileyhappy:

I understand, that real value can vary, but I need the first estimation.