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BOOSTXL-PGA460: How to increse the vpp?

Alexandre Becker Filho
Prodigy 220 points
Part Number: BOOSTXL-PGA460
Other Parts Discussed in Thread: PGA460

Hi,

I'm supplying BOOSTXL-PGA460 a voltage of 14V, but it only supply the TD40200D transducer with 90V. And i need at least 150V, what should i do to increase the voltage?

  • 0
    TI__Mastermind 27780 points

    Hi Alex,

    The transducer excitation voltage is controlled by both the center tap voltage of the transformer (which you have set to 14V) and the device's preset driver current limit value. The driver preset current limit value can be set from 50-500mA, whereby a larger current limit will generate a larger transducer excitation voltage. You can see the effects of the driver current limit in section "4.3 Current Limit" of the PGA460 Ultrasonic Module Hardware and Software Optimization app report.

  • 0 in reply to Akeem Whitehead
    Prodigy 220 points

    Thanks for the answer,

    I'm using a 14V/2A source. Do i have to change something in the circuit or software ?

  • 0 in reply to Alexandre Becker Filho
    TI__Mastermind 27780 points

    Alexandre,

    You do not need to change your hardware. You need to configure the preset driver current limit register values in software. The registers are named CURR_LIM_P1 and CURR_LIM_P2, can be set from 50-500mA.

  • 0 in reply to Akeem Whitehead
    Prodigy 220 points

    Thank you for the answer,

    I configured the preset driver current limit register values in software, but it didn't change the result. Then, i found this option in the device setting:  .It was activated. This option supplies the circuit with 500mA if it's necessary, right? 

  • 0 in reply to Alexandre Becker Filho
    TI__Mastermind 27780 points

    Hi Alex,

    To set the driver current limit to 500mA, use the "Driver Current Limit" option as shown: (491mA is ~500mA)

    You should notice a significant peak-to-peak driver voltage difference at the transducer for a driver current limit of 50mA versus 491mA. What is the peak-to-peak voltage at the transducer for 50mA vs 500mA?

    We do not recommend that you disable the current limit for the presets (keep this checkbox unchecked). This is an advanced used feature that expects the user to limit current externally, which the EVM hardware is not equipped to support. This would require custom hardware.

    I see that the TD40200D is dual frequency transducer. What frequency are you using? If it is 40kHz, you should be ok to use the existing transformer. I do recommend that you desolder the resistor (R38) and capacitor (C15) that are in parallel to the transducer, since these values are optimized for the Murata 58kHz transducer.

  • 0 in reply to Akeem Whitehead
    Prodigy 220 points

    The peak-to-peak voltage at the transducer for 50mA is 43V and for 500mA is 260V. For my aplication it's necessary only 40khz. 

     Look the diference before and after i desolded the resistor and capacitor.

    Before (using 12V source)

    After (using 14V source)

    Besides, what can i do to get real data in data monitor ?

  • 0 in reply to Alexandre Becker Filho
    TI__Mastermind 27780 points

    Hi Alex,

    The difference in your peak-to-peak sinusoidal driver integrity/shape can be influenced by the presence or lack of the matching components (parallel tuning capacitor and damping resistor) as described in section "3.4 Passive Tuning" of the PGA460 Ultrasonic Module Hardware and Software Optimization app report. Fine-tuning these values is a manual process. If the wave form looks better before the removal of the components, then re-install them.

    Your data monitor results appear to indicate there is a low-frequency (<1kHz) noise source near your ultrasonic setup, and is either coupling onto your power supply or transducer. Be sure there is not a laptop switching power supply, running motor, or other switch based power supply system near or sharing the same supply. Until you eradicate this low-frequency noise source in your environment, you will not be able to see the ultrasonic measurements. The cleanest setup to use is a 9V battery supply for the PGA460 EVM while your laptop is not connected to the wall power adapter. You can try this all battery configuration in a electrically quiet room to check if it is your current surrounding or bench supplies creating the noise.