topic PN7150 Power consumption in NFC

PN7150 Power consumption

daniel13 — Thu, 19 Jul 2018 20:15:14 GMT

Hi,

Our PN7150 design is setup for "configuration 1" where VBAT is connected to a 4.5V rail power supply and our TVDD configuration is: {0x20, 0x02, 0x07, 0x01, 0xA0, 0x0E, 0x03, 0x02, 0x1B, 0x00};

When measuring the current on the 4.5V rails during a read of a card (Mifare Classic & Desfire EV2 tested) we are seeing peak current of ~240mA.

From my understanding, there is a current limit on the VDD(TX) rail of 180mA according to the data sheet.

Is this current of ~240mA expected? (there is no other peripheral on the rail).

Where is the current measured on the VDD(TX) rail for its limit?

Thanks!

Attached is a screenshot of the current during polling, and with markers around the read (on the 4.5V rail).

Re: PN7150 Power consumption

daniel13 — Mon, 23 Jul 2018 14:05:56 GMT

Hi NXP team, has anyone had a chance to look at this?

Re: PN7150 Power consumption

daniel13 — Fri, 27 Jul 2018 18:44:22 GMT

Bump for visibility....

I can also explain any part that doesn't make sense.

Cheers,

Re: PN7150 Power consumption

Kan_Li — Mon, 30 Jul 2018 08:04:49 GMT

Hi Daniel,

240mA is out of the spec, please redo the antenna tuning, and you may refer to NFC Antenna Design for more details.

Hope that helps,

Have a great day,
Kan

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Re: PN7150 Power consumption

daniel13 — Wed, 22 Aug 2018 21:35:23 GMT

Hey Kan Li, looks like it did not need re-tuning but the issue was that I was not testing within the final enclosed assembly we originally tuned the antenna in — I had the PCBs open bare on my desk.

I'm assuming because of this, the antenna characteristics changed and became lower in impedance?

Once in the enclosure the max current is 120mA.

Also, from the user manual I saw a TXLDO_CFG to enable overcurrent detection. What does this enable exactly?

Cheers!