NFCのトピックPN5180 PLL setting

PN5180 PLL setting

smiwa — Fri, 17 Feb 2017 08:57:37 GMT

Hi,

I am now trying PN5180 operation by PLL with 12MHz crystal. (Before, I tried PN5180 with 27.26MHz and it can operated successfully.)

My question is how should I set the related register to operate PLL mode, because I cannot get 13.56MHz.

I confirmed the crystal is oscillating 12MHz. However, the frequency of RF out is also 12Mhz.

I think I miss some settings of necessary registers.

So, please tell me which register and/or which bit should be set and what value should be written?

I appreciate your advise as soon as possible.

Best regards,

S. Miwa

Re: PN5180 PLL setting

Jorge_Gonzalez — Tue, 28 Feb 2017 02:58:35 GMT

The PN5180 does not support external crystal other than 27.12 MHz.

Maybe you got confused by the fact that it supports an "external reference clock" of 8 MHz / 12 MHz / 16 MHz / 24 MHz. This is not a crystal.

If you wish to use the PLL with an external 12 MHz clock then you must update the settings via the EEPROM memory. To provide an accurate answer I am checking with the experts about what are the exact values you must save in EEPROM to use such configuration. Please let me reply back with their feedback.

Regards!

Jorge Gonzalez

Re: PN5180 PLL setting

smiwa — Tue, 28 Feb 2017 03:35:51 GMT

Hi Jorge san,

Understood and thank you for your clarification!

It is not clear description in datasheet. I misunderstood I can use the crystal other than 27.12MHz.

You mean I must use external clock or clock generator instead of crystal, right?

Anyway, please teach me how to set EEPROM parameter when I use the external clock.

Thank you for your support!

Best regards,

S. Miwa

Re: PN5180 PLL setting

Jorge_Gonzalez — Wed, 08 Mar 2017 00:30:10 GMT

Thank you for waiting.

An external clock can be used instead of the 27.12MHz crystal, although not recommended since it decreases Rx performance.

In any case if you want to connect an external clock please notice there is a mismatch in the datasheet. It shows the EEPROM options are 0x0 or 0x08:

This should be instead like next:

0x03 -> default = internal clock

0x00 -> external clock

The datasheet will be updated to reflect this.

Regards!

Jorge Gonzalez

Re: PN5180 PLL setting

janulo — Mon, 24 Apr 2017 05:51:20 GMT

Hi Jorge,

You wrote that using of external clock is not recommended, because it decreases Rx performance. What is the reason of decreased RX performance? Is there problem with lover precision of this clock signal?

We are using ext. clock on our reader (in development, so we don't have much experience to give you feedback regarding this ext. clock). This ext. clock signal is generated by MPU, MPU has crystal with accuracy meeting PN5180 requirements +/-100ppm. Is there any other reason for decreasing Rx performance other than frequency accuracy?