PN7150 - Standby Mode

[adrianpakosinsk]

Hello,

I have a question about standby mode in the   PN7150 chip. I have a running example NXP-NCI LPCXpresso example (SW3241) - NXP-NCI_LPC11xx_example on my uC. I would like very low current consumption on my device so I want to use standby mode. Theoretically, it is enabled. Below a snippet of code and send command and response from PN7150.

NxpNci_CORE_STANDBY[]={0x2F, 0x00, 0x01, 0x01};    /* last byte indicates enable/disable */

...

NCI >>  0x2f  0x00  0x01  0x01
NCI <<  0x4f  0x00  0x01  0x00

...

I measured current on the oscilloscope. These  waveforms show voltage drop on 1 Ohm resistor.

The first graph shows current on listening  mode and the second when  the  card is reading.

As you can see Imax = 223mA. This is a value that is not consistent with the catalog note. I will add that when I  disable standby mode (NCI >>  0x2f  0x00  0x01  0x00). The waveforms looked the same, the current has the same value.  Why the current is so large? What could be the reason?

Best Regards,

Adrian Pakosinski

[Kan_Li]

Hi Adrian,

Would you please specify on which platform you measured the voltage, OM5578 or a custom board? please help to clarify.

Have a great day,
Kan

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[adrianpakosinsk]

Hi Kan,

Thank you for your interest. These measurements come from custom board but also I made measurements on OM5578. On OM5578 the charts were similar shape but the voltage was smaller, exactly 120mV when the   card is reading.

Thanks,

Adrian

[Kan_Li]

Hi Adrian,

I think it would be possibly a hardware design issue, please kindly refer to http://www.nxp.com/documents/application_note/AN11756.pdf for reference.

Hope that helps,

Have a great day,
Kan

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Note: If this post answers your question, please click the Correct Answer button. Thank you!
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[adrianpakosinsk]

Thank you for your answer. I read this document and followed the recommendations. Is the current 120mA taken by OM5578 is a  normal value?  (when the card is reading). Maybe on my custom board is some hardware design issue but I think on OM5578 everything should be fine.

Thanks,

Adrian