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PGA460-Q1: BOOSTXL-PGA460 EVM

Part Number: PGA460-Q1
Other Parts Discussed in Thread: BOOSTXL-PGA460, PGA460

Hi,

Im working with BOOSTXL-PGA460 Evaluation kit at 300KHz, integrated with Airmar AT300 and B78416A2386A003, while C15 and R38 are removed.

I was wondering how I can shorten the period of the transducer boost by sharpening the descending part of the signal shown in the data dump plot. It takes 0.43 ms now which makes the detection of the objects closer than 7cm impossible. I am using LP-USB for this results, memory map is also included. Decreasing the number of the pulses or playing with current limit did not help to improve anymore.

  • GRID_USER_MEMSPACE-2021-09-03_094400-record.txt
    ;GRID_USER_MEMSPACE
    00 (USER_DATA1),00
    01 (USER_DATA2),00
    02 (USER_DATA3),00
    03 (USER_DATA4),00
    04 (USER_DATA5),00
    05 (USER_DATA6),00
    06 (USER_DATA7),00
    07 (USER_DATA8),00
    08 (USER_DATA9),00
    09 (USER_DATA10),00
    0A (USER_DATA11),00
    0B (USER_DATA12),00
    0C (USER_DATA13),00
    0D (USER_DATA14),00
    0E (USER_DATA15),00
    0F (USER_DATA16),00
    10 (USER_DATA17),00
    11 (USER_DATA18),00
    12 (USER_DATA19),00
    13 (USER_DATA20),00
    14 (TVGAIN0),10
    15 (TVGAIN1),01
    16 (TVGAIN2),44
    17 (TVGAIN3),FD
    18 (TVGAIN4),F8
    19 (TVGAIN5),61
    1A (TVGAIN6),85
    1B (INIT_GAIN),7F
    1C (FREQUENCY),64
    1D (DEADTIME),00
    1E (PULSE_P1),06
    1F (PULSE_P2),12
    20 (CURR_LIM_P1),64
    21 (CURR_LIM_P2),7F
    22 (REC_LENGTH),0C
    23 (FREQ_DIAG),00
    24 (SAT_FDIAG_TH),EE
    25 (FVOLT_DEC),7C
    26 (DECPL_TEMP),0A
    27 (DSP_SCALE),00
    28 (TEMP_TRIM),00
    29 (P1_GAIN_CTRL),12
    2A (P2_GAIN_CTRL),00
    2B (EE_CRC),6D
    40 (EE_CNTRL),00
    41 (BPF_A2_MSB),2C
    42 (BPF_A2_LSB),81
    43 (BPF_A3_MSB),F9
    44 (BPF_A3_LSB),A5
    45 (BPF_B1_MSB),03
    46 (BPF_B1_LSB),2D
    47 (LPF_A2_MSB),7E
    48 (LPF_A2_LSB),67
    49 (LPF_B1_MSB),00
    4A (LPF_B1_LSB),CD
    4B (TEST_MUX),00
    4C (DEV_STAT0),80
    4D (DEV_STAT1),00
    5F (P1_THR_0),00
    60 (P1_THR_1),11
    61 (P1_THR_2),22
    62 (P1_THR_3),23
    63 (P1_THR_4),2E
    64 (P1_THR_5),28
    65 (P1_THR_6),FF
    66 (P1_THR_7),D4
    67 (P1_THR_8),62
    68 (P1_THR_9),94
    69 (P1_THR_10),A5
    6A (P1_THR_11),28
    6B (P1_THR_12),28
    6C (P1_THR_13),28
    6D (P1_THR_14),69
    6E (P1_THR_15),09
    6F (P2_THR_0),EE
    70 (P2_THR_1),30
    71 (P2_THR_2),87
    72 (P2_THR_3),26
    73 (P2_THR_4),81
    74 (P2_THR_5),4D
    75 (P2_THR_6),93
    76 (P2_THR_7),EE
    77 (P2_THR_8),A0
    78 (P2_THR_9),AA
    79 (P2_THR_10),8C
    7A (P2_THR_11),39
    7B (P2_THR_12),DC
    7C (P2_THR_13),1E
    7D (P2_THR_14),1D
    7E (P2_THR_15),5E
    7F (THR_CRC),A2
    EOF
    

If I switch to using an external power supply, which one would determine the driver current limit, the software or the external power supply? Since AT300 has Vmax=200Vpp,  I tried to produce a stronger transducer boost by increasing the driver current limit, but although I see a higher amplitude in oscilloscope, the data path value in plot data dump wont increase and I have to use x4 SR Gain.

Thanks

  • Hi Zeinab,

    Our team is out today for a holiday.  We should be able to respond tomorrow when we are back.

    Regards,

    Mekre

  • Hi Zeinab,

    In addition to reducing the number of pulses and adjusting the current limit, the following also reduces the transducer ring-decay time:

    • Selecting a higher frequency transducer. Please note that this higher frequency must still be less than the maximum 480 kHz transducer frequency supported by the PGA460.
    • Using a damping resistor and tuning capacitor.  Section 4.4 of the SLAA732 application note provides more info on how to do this.
    • Using a bi-static configuration. This two-transducer configuration uses one transmitter as a dedicated transmitter while another transmitter is a dedicated receiver.    Figure 4-1 of SLAA732 shows an example of a bi-static configuration. 

    Regards,

    Mekre

  • Thanks for the tips,

    considering the Airmar AT300 being one of the suggested transducers by TI, any idea what would be the closest estimation for R and C values? Also, If I go for higher frequencies, any suggestion for the attributed transformer?

    Regards,

  • Hi Zeinab,

    The following spreadsheet lists possible transducers and transformers: https://www.ti.com/lit/zip/slac787

    The recommended transducer frequency column in the transformer tab provides a recommended transducer frequency range for each transformer.  After selecting the transformer, I recommend testing it at the desired frequency to see that it meets your requirements.

    We do not have recommendation for the damping resistor value.  Optimizing this resistance is done through an arbitrary process of monitoring the decay profile by trial and error.  Since the value of RDAMP ranges from 500 Ω to 25 kΩ, I recommend using a potentiometer to sweep and fine-tune the value based on the minimum distance you want to detect.  The following training video also provides more info on the tuning process:

    https://training.ti.com/ti-precision-labs-ultrasonic-sensing-ultrasonic-transducer-tuning?context=1139747-1139746-1147829-1147821

    Regards,

    Mekre