ST25R3916B abnormal power consumption in the wakeup mode

[ShimiaoWang]

I am testing power consumption. The hardware is using nucleo-L476 and X-NUCLEO-NFC08A1, and the software is using the NFC06A1_PollingTagDetect routine from X-CUBE-NFC6. The test revealed that the average power consumption was 180 uA when entering the wakeup. I was using a 3.3V power supply. The minimum current is 40 uA.

I'm not sure how to make the necessary modifications to achieve the description in AN5320.

[Brian TIDAL]

Hi,

The typical value of the supply current in Ready mode (I_RD) in the datasheet is measured with the following configuration for VDD = 3.3 V:

• Register 00h to 07h (no clock on MCU_CLK)
• Register 01h to C0h (3 V supply mode, VDD_D disabled)
• Register 02h to 80h (en = 1)
• Register 2Ch to D8h (3.0 V regulator)

See footnote 6 in table 125 of the datasheet.

The configuration used in the X-CUBE-NFC6 firmware is defined in analogConfigTbl_NFC08A1.c (CHIP_INIT section) and uses regulated voltages defined by the result of the Adjust Regulators command, AAT, and a pull-down on SPI. The value of the supply current in Ready mode I_RD is therefore different.

Rgds

BT

[ShimiaoWang]

Hi

 Thank you for your reply.

Based on the register configuration in the data manual, the current under this configuration is over 40 microamperes. Is there any hardware modification required?

[Ulysses HERNIOSUS · Accepted solution]

Hi ShimiaoWang,

I think you are running into issues due to the varicaps being mounted on the board. The issue will happen no matter which value being output on AAT_A and AAT_B. 

To remove this current you can:

1. Remove the varicaps and compensate by increasing the normal caps
2. Set driver to high resistance (d_res=0xf), e.g. write register 28h to 0x0f.

BR, Ulysses

[ShimiaoWang]

Hi Ulysses HERNIOSUS

Thank you for your suggestion.

I remove the varicaps and The configuration of rfalAnalogConfigCustomSettings array. The power consumption of the current 200ms wakeup mode has been reduced to 36ua.

To achieve 25ua in AN5320, do you think there are any other possible modification points? Or do I need to adjust the NFC matching network?

[Ulysses HERNIOSUS]

Hi ShimiaoWang,

the I_A,AVG cannot be directly measured. What you are measuring is the overall average current which always includes also I_WU and I_OSC,AVG: 

(typo: I_OSC,AVG missing before I_WU).

BR, Ulysses

[ShimiaoWang]

Hi Ulysses HERNIOSUS

Thank you for your guidance. I understand now