NXP NFC Controllers: Meaning/Measuring of the conductance for the P-driver/N-driver of the antenna driver pins TX1 and TX2

[oliviermartin]

I have been going through few NXP NFC controllers datasheet and application notes. And I have not really found how to understand/measure what is named as the conductance for the N-driver of the antenna driver pins TX1 and TX2.

From what I have found, the P/N-driver is related to MOSFET transistor. But what the link between the antenna and the MOSFET transistor?

I would like to understand where to get these 5 parameters:

- CWGsNOff (part of GsNOffReg): The value of this register defines the conductance of the output N-driver during times of no modulation.

- ModGsNOff (part of GsNOffReg): The value of this register defines the conductance of the output N-driver for the time of modulation.

- CWGsNOn (part of GsNOnReg): The value of this register defines the conductance of the output N-driver during times of no modulation

- ModGsNOn (part of GsNOnReg): The value of this register defines the conductance of the output N-driver for the time of modulation.

- CWGsP (part of CWGsPReg): The value of this register defines the conductance of the output P-driver.

[Jorge_Gonzalez]

Hello Olivier Martin:

The conductance parameters are indeed related to the TX1 and TX2 P and N output drivers.

- The CW conductance parameters are used to control output power and current consumption.

- The Mod conductance parameters are used to configure the modulation index of the carrier wave.

There is really not a formula or measurement to set these registers, as this will depend on your board, your requirements (power consumption vs read/write distance, target card sensitivity, etc) and the antenna matching. You can experiment by writing to the registers and observing the resulting output signal, either in continuous mode (no modulation) or with a modulating signal. There are tables for TX1 and TX2 behavior according to register settings:

For antenna design there is a series of videos. The first one is in the next link:

Which Antenna for what purpose|NXP

Best Regards!

Jorge Gonzalez