Low power mode ST25R95, power consumption?

[DGrgic]

Hello,

I'm using ST25R95 in my project. I'm sending pulse signal in order to transit from powerUP mode, and after it the Idle command in order to enter hibernate mode.

Idle command: {0x07, 0x0E, 0x08, 0x04, 0x00, 0x04, 0x00, 0x18, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

I'm using custom PCB and current consumption after I send Idle command drops from 1.69mA to 1.14mA.

The rest of circuit on the PCB consumes 0.14mA, which means there is about 1mA current somewhere in the NFC circuit.

In the DB2382 Rev 5 document, I have found reference design for the ST25R95, and SSI_0 is connected over 3.3kOhms to VCC, and SSI_1 over 3.3kOhms to GND. That is the only difference from mine design, because I have connected those 2 pins directly to VCC and GND respectively (SSI_0 to VCC, and SSI_1 to GND). Could this be an issue and is that reason for this 1mA power consumption, or do I need to do something else besides sending the Idle command?

Best regards and thank you in advance,

Dragan

[Brian TIDAL]

Hi @DGrgic​ 

the Idle command seems correct.

I would suggest to compare your schematics with the X-NUCLEO-NFC03 ones (see UM2479 for the schematics) and use the same pull up/down resistors. You can first measure the current consumption on X-NUCLEO-NFC03 in case of any doubts.

Also, please make sure to rely on IRQ_OUT before reading the answer to the Idle command (i.e. SPI poll cannot be used while in low power and Application has to rely on IRQ_OUT, see Datasheet §5.9)

Rgds

BT

[DGrgic]

Hello @Brian TIDAL_O​ ,

Thank you for your response.

After we send the Idle command, the IRQ_OUT pin remains in a HIGH state, so we don't try to read the response with SPI.

If the device is sent in hibernate mode, using the Idle command is it supposed to answer?

[Ulysses HERNIOSUS]

Hi Dragan,

the response to Idle command can only be read once IRQ_OUT went low. Please refer to Table 24 in DS.

Regards, Ulysses