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RF430FRL152H: Cant read via NFC when battery disconnected

Kadas
Prodigy 10 points

Part Number: RF430FRL152H
Other Parts Discussed in Thread: , MSP-EXP430G2ET, DLP-7970ABP

Tool/software:

Hi,

Im having loads of trouble with my custom board featuring the RF430FRL152H. The core of the problem: NFC refuses to read when the battery supply is disconnected (regulated LDO 1.5V from a battery). What i found so far:
1. VDDSW seems to reach only 1.3V when powered only by RF (VDDH is fine, at 1.8V) and NFC doesn't read.

2. When reading NFC with the battery supply, VDDSW reaches 1.5V and it reads fine.

3. LC is tuned, verified with a VNA

4. Removed all possible loads (disconnected all my sensors and so on).

Already tried increasing the cap at VDDSW from 2.2uF to ~6uF.

Now the most interesting part: when i first soldered the RF430, NFC was reading fine WITHOUT the battery and with each read it deteriorated until now i can only read with the battery supply and it happened twice with a newly soldered chip, like what is going on? Slight smile

Any help or insights would be greatly appreciated.
P.S. the circuit is designed according to the datasheet example.

  • 0
    TI__Guru**** 191886 points

    Hi,

     I'm currently on vacation and I will reply to your question when I come back on Thursday. Please expect delay in my response.

  • 0
    TI__Guru**** 191886 points

    Hi,

      - Do you have the battery connected when you use the RF power?

      - When you measure 1.3V on VDDSW, which power mode are you operating in?

      - Which reader are you using? 

      - Do you have the same problem reading the RF430FRL152HEVM?

      - Do you have the reader using DLP-7970ABP BoosterPack plug-in module and MSP-EXP430G2ET LaunchPad development kit? If you use this reader, do you see the same problem?

    Kadas said:
    Now the most interesting part: when i first soldered the RF430, NFC was reading fine WITHOUT the battery and with each read it deteriorated until now i can only read with the battery supply and it happened twice with a newly soldered chip,

    I'm not clear as to what is deteriorated? Is the battery deteriorated? Earlier you said when reading with the battery it was reading fine with the battery at 1.5V. Or you are saying the battery is deteriorated and if you replace with a new battery then it starts to read fine again?

    Kadas said:
    P.S. the circuit is designed according to the datasheet example.

    ok. 

  • 0 in reply to Charles Tsai
    TI__Guru**** 191886 points

    Hi,

     Do you have any update?

  • 0 in reply to Charles Tsai
    Prodigy 10 points

    Hello,

    Yes, sorry for the late update, i have resolved all issues. One problem was solder bridging under the chip due to mistakes when soldering. Was hard to catch because it happened twice and had identical symptoms, resoldering again solved some of the problems.

    Also, a big part of the problem was an oversight in the code, when powering via RF it was loading the I2C module and disabling RF functionality/draining too much power, the remaining problems when away when i added a simple guard to return if the chip is powered from the RF field.

    Thank you for you help!