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PGA460: PGA460 200Khz Solution Problem

Farzan Saleem71
Prodigy 85 points
Part Number: PGA460

Hi,

We are developing 200khZ solution based on pga460 and have a few queries about it.

Our transducer is 200khz. but the device firmware always detects 250kHz. (Sometimes inf). Distance is always static at 1024cm

Please find attached our reference schematic, PCB design and the data sheet of the transducer that we are using.

  • we are testing the system on 12 V
  • TI recommenced transformer was not available so we have used alternative part previously approved by you.

Following parts are used in the development of solution.

PH9185.013NL (Transformer)

SS320LWHRVG (Diodes)

TLV61064A (Supply @ 12V)

Following is my register settings (I am also writing BPF and LPF using register write command )

14 (TVGAIN0),44
15 (TVGAIN1),44
16 (TVGAIN2),44
17 (TVGAIN3),08
18 (TVGAIN4),64
19 (TVGAIN5),9A
1A (TVGAIN6),99
1B (INIT_GAIN),C0
1C (FREQUENCY),11
1D (DEADTIME),40
1E (PULSE_P1),04
1F (PULSE_P2),86
20 (CURR_LIM_P1),3F
21 (CURR_LIM_P2),D5
22 (REC_LENGTH),03
23 (FREQ_DIAG),00
24 (SAT_FDIAG_TH),EE
25 (FVOLT_DEC),7C
26 (DECPL_TEMP),0F
27 (DSP_SCALE),00
28 (TEMP_TRIM),00
29 (P1_GAIN_CTRL),11
2A (P2_GAIN_CTRL),00
2B (EE_CRC),7A
40 (EE_CNTRL),00
41 (BPF_A2_MSB),E1
42 (BPF_A2_LSB),FF
43 (BPF_A3_MSB),F3
44 (BPF_A3_LSB),72
45 (BPF_B1_MSB),06
46 (BPF_B1_LSB),47
47 (LPF_A2_MSB),7C
48 (LPF_A2_LSB),D3
49 (LPF_B1_MSB),01
4A (LPF_B1_LSB),97
4B (TEST_MUX),00
4C (DEV_STAT0),80
4D (DEV_STAT1),00
5F (P1_THR_0),20
60 (P1_THR_1),00
61 (P1_THR_2),22
62 (P1_THR_3),22
63 (P1_THR_4),22
64 (P1_THR_5),22
65 (P1_THR_6),FC
66 (P1_THR_7),E4
67 (P1_THR_8),62
68 (P1_THR_9),10
69 (P1_THR_10),84
6A (P1_THR_11),20
6B (P1_THR_12),20
6C (P1_THR_13),20
6D (P1_THR_14),20
6E (P1_THR_15),07
6F (P2_THR_0),20
70 (P2_THR_1),00
71 (P2_THR_2),22
72 (P2_THR_3),22
73 (P2_THR_4),22
74 (P2_THR_5),22
75 (P2_THR_6),FC
76 (P2_THR_7),E4
77 (P2_THR_8),62
78 (P2_THR_9),10
79 (P2_THR_10),84
7A (P2_THR_11),20
7B (P2_THR_12),20
7C (P2_THR_13),20
7D (P2_THR_14),20
7E (P2_THR_15),07
7F (THR_CRC),11

Transducer_Datasheet.pdfSchematic.pdfPCB.pdf

  • 0
    TI__Genius 11015 points
    Farzan,

    We have received your question & we will get back with you by next week.
  • 0
    TI__Mastermind 27950 points
    Hi Farzan,

    A few questions/suggestions I have:

    1) How did you set the BPF_A2_MSB and _LSB values? More specifically, how did you set/calculate the _LSB=0xFF? This should still work, but you can also refer to the High Freq BPF Coefficient table under the GUI's top menu File for coefficient values based on frequency and BPF bandwidth. You can manually register write these values into the coefficient register space. I recommend BPF_A2_MSB=0xE0 and _LSB=0x03 based on your settings.

    2) In your schematic, I see two diodes (D1 and D2) at the secondary of the transformer. It looks like you used the Application schematic from the PH9185.013NL datasheet, but I don't think this configuration will work. Instead, you can get rid of both D1 and D2, and connect the transformer's pin 2 to ground, leave pin 5 floating, and pin 6 to the XDCR+ pin. Refer to "PGA460 Mono-static Transducer Transformer Driver Small Form Factor Design File" ( www.ti.com/.../slac754 ) for an example schematic of your mono-static transformer use-case.

    3) What does the waveform at the transducer look like with your current configuration? It should be a sinusoidal waveform at XDCR+. After you make the modification I described above, do the results vary?

    4) The transducer specs are typical for the high-frequency applications of the PGA460. I suspect that after you re-work your driver schematic, the 200kHz response will be captured. Also, your frequency diagnostics are disabled based on the memory map grid file you attached. The Frequency Diagnostic's Window Length period needs to be a non-zero value to enable the frequency diagnostic. Try a Freq Diag Window Length of 6, and a Freq Diag Start Time of 300us.
  • 0 in reply to Akeem Whitehead
    Prodigy 85 points
    Thank you sou much for your time.You are great help.I will get back to you with results.
  • 0 in reply to Farzan Saleem71
    TI__Genius 11015 points
    FArzan,

    I will close this thread for now, hope my suggests helps you.

    Please start a new thread if you have any further questions.