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BLE DTM test fail - Delta F2 Max out of spec in TRM-LE/CA/05/C Modulation Characteristics test

weiji jiang
Expert 2040 points
Other Parts Discussed in Thread: CC2540, CC2541

Hi TI Folks,

  When I conduct BLE Modulation Characteristics test refer to TRM-LE/CA/05/C test standard below, the Delta F2 Max is out of spec, and the Power is out of spec too, please advise , what is the possible to cause this NG, and how to improve.

--------------------------------------Test Result---------------------------------------

Start:    

1. ATC_CONNECT_TESTER
    Serial number:
    Test time: 0.03sec

2. ATC_INSERT_DUT
    Technology: BT
    DUT DLL: TI_CC2540_41.dll
    DUT_VERSION=1.0.4 (2011-4-20)
    Test time: 0.02sec

3. ATC_INITIALIZE_DUT
    Technology: BT
    DUT_NAME=TI BT
    Test time: 0.01sec

4. ATC_TESTER_OBTAIN_CONTROL
    Test time: 0.01sec

5. BT_TX_LE
    Frequency: 2402,Packet Type: 1LE, Tx Power: 0.0

    Ini Freq Error      108.932 KHz         (150.0 ~ -150.0)    <-- pass
    Delta F2 Avg        229.894 KHz         (320.0 ~ 185.0)     <-- pass
    Delta F2 Max        196.624 KHz         (320.0 ~ 185.0)     <-- pass
    Delta F0 Fn Max     7.021 KHz           (50.0 ~ 0.0)        <-- pass
    Delta F1 F0         2.393 KHz           (20.0 ~ 0.0)        <-- pass
    Delta Fn Fn5 Max    8.120 KHz           (20.0 ~ 0.0)        <-- pass
    Power               -6.553 dBm          (5.0 ~ -5.0)        <-- fail
    Delta F1 Avg        245.916 KHz         (275.0 ~ 225.0)     <-- pass
    Ratio of F2 To F1   0.935               (10.0 ~ 0.8)        <-- pass
    Retry 1:

    Ini Freq Error      104.301 KHz         (150.0 ~ -150.0)    <-- pass
    Delta F2 Avg        230.539 KHz         (320.0 ~ 185.0)     <-- pass
    Delta F2 Max        194.748 KHz         (320.0 ~ 185.0)     <-- pass
    Delta F0 Fn Max     13.289 KHz          (50.0 ~ 0.0)        <-- pass
    Delta F1 F0         7.699 KHz           (20.0 ~ 0.0)        <-- pass
    Delta Fn Fn5 Max    10.309 KHz          (20.0 ~ 0.0)        <-- pass
    Power               -6.546 dBm          (5.0 ~ -5.0)        <-- fail
    Delta F1 Avg        244.902 KHz         (275.0 ~ 225.0)     <-- pass
    Ratio of F2 To F1   0.941               (10.0 ~ 0.8)        <-- pass
    Retry 2:


6. BT_TX_LE
    Frequency: 2442,Packet Type: 1LE, Tx Power: 0.0

    Ini Freq Error      115.681 KHz         (150.0 ~ -150.0)    <-- pass
    Delta F2 Avg        234.642 KHz         (320.0 ~ 185.0)     <-- pass
    Delta F2 Max        185.470 KHz         (320.0 ~ 185.0)     <-- pass
    Delta F0 Fn Max     8.213 KHz           (50.0 ~ 0.0)        <-- pass
    Delta F1 F0         5.753 KHz           (20.0 ~ 0.0)        <-- pass
    Delta Fn Fn5 Max    7.903 KHz           (20.0 ~ 0.0)        <-- pass
    Power               -5.985 dBm          (5.0 ~ -5.0)        <-- fail
    Delta F1 Avg        245.382 KHz         (275.0 ~ 225.0)     <-- pass
    Ratio of F2 To F1   0.956               (10.0 ~ 0.8)        <-- pass
    Retry 1:

    Ini Freq Error      118.661 KHz         (150.0 ~ -150.0)    <-- pass
    Delta F2 Avg        236.159 KHz         (320.0 ~ 185.0)     <-- pass
    Delta F2 Max        189.950 KHz         (320.0 ~ 185.0)     <-- pass
    Delta F0 Fn Max     15.975 KHz          (50.0 ~ 0.0)        <-- pass
    Delta F1 F0         7.785 KHz           (20.0 ~ 0.0)        <-- pass
    Delta Fn Fn5 Max    9.568 KHz           (20.0 ~ 0.0)        <-- pass
    Power               -6.001 dBm          (5.0 ~ -5.0)        <-- fail
    Delta F1 Avg        245.844 KHz         (275.0 ~ 225.0)     <-- pass
    Ratio of F2 To F1   0.961               (10.0 ~ 0.8)        <-- pass
    Retry 2:

7. BT_TX_LE
    Frequency: 2480,Packet Type: 1LE, Tx Power: 0.0

    Ini Freq Error      111.666 KHz         (150.0 ~ -150.0)    <-- pass
    Delta F2 Avg        235.486 KHz         (320.0 ~ 185.0)     <-- pass
    Delta F2 Max        186.532 KHz         (320.0 ~ 185.0)     <-- pass
    Delta F0 Fn Max     10.044 KHz          (50.0 ~ 0.0)        <-- pass
    Delta F1 F0         3.988 KHz           (20.0 ~ 0.0)        <-- pass
    Delta Fn Fn5 Max    7.159 KHz           (20.0 ~ 0.0)        <-- pass
    Power               -9.132 dBm          (5.0 ~ -5.0)        <-- fail
    Delta F1 Avg        246.865 KHz         (275.0 ~ 225.0)     <-- pass
    Ratio of F2 To F1   0.954               (10.0 ~ 0.8)        <-- pass
    Retry 1:

    Ini Freq Error      115.053 KHz         (150.0 ~ -150.0)    <-- pass
    Delta F2 Avg        239.056 KHz         (320.0 ~ 185.0)     <-- pass
    Delta F2 Max        172.172 KHz         (320.0 ~ 185.0)     <-- fail
    Delta F0 Fn Max     5.504 KHz           (50.0 ~ 0.0)        <-- pass
    Delta F1 F0         0.686 KHz           (20.0 ~ 0.0)        <-- pass
    Delta Fn Fn5 Max    8.257 KHz           (20.0 ~ 0.0)        <-- pass
    Power               -8.825 dBm          (5.0 ~ -5.0)        <-- fail
    Delta F1 Avg        246.371 KHz         (275.0 ~ 225.0)     <-- pass
    Ratio of F2 To F1   0.970               (10.0 ~ 0.8)        <-- pass
    Retry 2:


8. BT_RX_LE
    Frequency: 2402, Packet Type: 1LE, Rx Power: -50.0
    PER                 0.000 %             (10.0 ~ 0.0)        <-- pass
    Test time: 1.66sec

9. BT_RX_LE
    Frequency: 2442, Packet Type: 1LE, Rx Power: -50.0
    PER                 0.000 %             (10.0 ~ 0.0)        <-- pass
    Test time: 1.60sec

10. BT_RX_LE
    Frequency: 2480, Packet Type: 1LE, Rx Power: -50.0
    PER                 0.000 %             (10.0 ~ 0.0)        <-- pass
    Test time: 1.59sec

11. ATC_WRITE_MAC_ADDRESS
    Write MAC skip, because of testing failed

12. ATC_READ_MAC_ADDRESS
    DUT BD address: 67-44-33-22-11-00
    Test time: 0.11sec

13. ATC_TESTER_RELEASE_CONTROL
    Test time: 0.02sec

14. ATC_REMOVE_DUT
    Technology: BT
    Test time: 0.03sec

        *****************
        **** F A I L ****
        *****************

End:      

-----------------------------------------------------------------------------------------------------------

Best regards

Jiang WeiJi

  • 0
    Expert 2040 points
    Hi TI Folks,
    Good afternoon. Don't know why the photo of TRM-LE/CA/05/C Modulation Characteristics can't display in above post, So I write down the information of TRM-LE/CA/05/C Modulation Characteristics in below:

    ---------------------TRM-LE/CA/05/C Modulation Characteristics Test for BLE-----------------------
    Puropose:This test verifies that the modulation characteristics of the transmitted signal are correct.
    Packet:LE
    Payload:11110000 for Delta F1 , 1010 for Delta F2
    Judgement standard:
    225 kHz <=Delta F1 Avg <=275 kHz
    Delta F2 Max ≥ 185 kHz
    Delta F2 Avg / Delta F1 Avg ≥ 0.8
    --------------------------------------------------------End--------------------------------------------------

    Best regards
    Jiang WeiJi
  • 0 in reply to weiji jiang
    TI__Guru** 105180 points
    Hello WeiJi,

    Does this test pass on TI Reference HW? Can you post your schematic & layout?

    Best wishes
  • 0 in reply to weiji jiang
    TI__Guru** 106705 points
    Hi Jiang,

    For Delta F2 max you only need 99.9% of the symbols above 185 kHz. It is not clear from your testing how many symbols are below the limit. What tester are you using? Can you check your setup to see if it is possible to see the rate of symbols above the limit?

    In the few cases where I have seen this fail on the CC254x it has always been due to noise on the power supply rail, typically due to a poorly laid out boost converter. Are you using a regulator in your design?

    Cheers,
    Fredrik
  • 0 in reply to Fredrik K
    Expert 2040 points
    Hi Fredrik,

    I summary the NG from the test report.
    Test condition: Frequency: 2480,Packet Type: 1LE, Tx Power: 0.0
    1. Delta F2 Max 172.172 KHz (320.0 ~ 185.0) <-- fail ==> Spec is 320.0 ~ 185.0, Actual is 172.172 KHz , result is out of spec
    2. Power -8.825 dBm (5.0 ~ -5.0) <-- fail ==> Spec is 5.0 ~ -5.0, Actual is -8.825 dBm , result is out of spec

    The Delta F2 Max and Power is a bit lower, Please advise what is the key factor to cause like that.

    Best regards
    Jiang WeiJi
  • 0 in reply to weiji jiang
    TI__Guru** 106705 points
    Hi Jiang,

    As I said in my previous post, one single delta F2 max value below 185 kHz is not a failure. You are allow to have 0.1% of the values (for 10 test packets) below 185 kHz. The number of delta F2 max values below 185 kHz is not clear from your test results, and it is thus not possible to say if it is a real failure or not.

    That being said, the CC2540 should typically pass this test with 100% good values. Again, as I mentioned in my previous post, the cause of such failures is typically poorly designed (boost) regulators. You did not answer whether you are using a regulator or not. Poor RF ground layout can also cause such problems.

    The low output power can be because of anything from poor RF matching after the balun, poor layout of the RF circuitry in general, poor RF ground plane to how you connect the board to the test system. This is however not a failure from a BT spec point of view. It just says "fail" because you have arbitrarily set the low limit to -5 dBm. This is not a BT spec requirement.

    Cheers,
    Fredrik
  • 0 in reply to Fredrik K
    Expert 2040 points

    Hi Fredrik,

      Good day to you.

      Thanks for your information and advice on "delta F2 max". 

       About the output power matter, after we change a qualified cable for connection between DUT (CC2541 PCBA) and Tester system, the output power result is stable around -2.5 dbm.  

     Because our product design is reference to "CC2541 Mini Development Kit", So please share the output power information of this EVM board.  So that we can understand how much difference between the EVM and our design.

    best regards

    Jiang WeiJi

  • 0 in reply to weiji jiang
    TI__Guru** 106705 points
    Hi Jiang,

    The typical conducted output power for the Keyfob is 0 dBm. Note that there are chip to chip variations, so -2.5 dBm on one unit is within the expected tolerance.

    Cheers,
    Fredrik
  • 0 in reply to Fredrik K
    Expert 2040 points
    Hi Fredrik,

    Thanks for quickly reply.
    May I know if we only consider on CC2541 chip, How much is its tolerance ? Because we want to know how many margin in the existing design.

    Best regards
    Jiang WeiJi
  • 0 in reply to weiji jiang
    TI__Guru** 106705 points
    Hi Jiang,

    As CC2541 is one our older devices, typical tolerance is within +/- 4 dBm.

    Cheers,
    Fredrik
  • 0 in reply to Fredrik K
    Expert 2040 points

    Hi Fredrik,

      Good day to you.

      Thanks for your information sharing.

      I have a question on the output power variety between 2402MHZ and 2480MHZ, see below test result

    We can see the output power variety is about 1.x dBm between 2402MHz and 2480Mhz, please teach is it a problem here?

    And if want to improve it, what is the consideration factor?  By the way, the RF circuit layout we already follow 50 ohm impedance guidance.

    and below is the PCB info:

    And RF schematic is as below:

     Please advise on the value of C8,C10,L1,C11, C9, L4, L2, C12 and L3 for improvement.

    best regards.

    Jiang WeiJiE2E output power not steady.docx

  • 0 in reply to weiji jiang
    TI__Mastermind 18780 points
    The variation in output power vs freq is as expected, see figure 19 p22 in the datasheet www.ti.com/.../cc2541.pdf.
  • 0 in reply to CHS
    Expert 2040 points
    Hi Charlotte,

    Good day to you.

    Thanks for your important information. Refer to datasheet variant data, It helps me to clarify that the power output performance of my design is no problem. Till now can judge project design win.

    Thank you for your strong support again.


    Best regards.

    Jiang WeiJi