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BOOSTXL-PGA460: Voltage rating of C_INP and C_INN

Nicola Bizzotto
Prodigy 40 points
Part Number: BOOSTXL-PGA460
Other Parts Discussed in Thread: PGA460

Hello,

I'm currently evaluating PGA460 through BOOSTXL-PGA460 EVM and testing some high frequency and high voltage-rated transducers (300kHz and 400kHz resonance frequency, with 400Vpp maximum driving voltage).

As my requirements are short range distance measurements, I already tested the transducers with the direct-driven topology. Now I would like to test the same transducers with a higher driving voltage, by using the transformer-driven method. I'm actually exciting the transducers with about 200Vpp, but for now I've not connected the transducer itself to PGA460's receiver inputs. The reason for this is that I am unsure about the required voltage rating for C_INP and C_INN. By now I understood that C_INP is there to limit the current flowing to PGA460's receiver input stage and also remove DC bias; C_INN should have mainly noise filtering purposes. I have already calculated the optimal C_INP and C_INN value, as suggested in Table 8-2 of PGA460's datasheet.

C_INP and C_INN included in BOOSTXL-PGA460 have 50V voltage rating; are C_INP and C_INN capacitors voltage rating something I should worry about when driving transducers with more than 50V? How is the voltage rating of these capacitors related to driving voltage?

I hope I managed to express clearly what my doubts are.

Thanks in advance for your attention.

Best regards.

  • 0
    TI__Mastermind 21050 points

    Hello Nicola,

    Thank you for posting to the sensors forum! 

    If you are using a monostatic topology where the same transducer is used to drive the transducer and receive the signal the C_INP and C_INN capacitors ratings are something you should be mindful of. The main concern would be that C_INP and the transducer output are connected so this capacitor would receive all 200Vpp provided to the transducer so this capacitor should be rated appropriately and should be able to handle any overshoot that may occur. The C_INN capacitor receives some voltage but not as large as the C_INP so its still recommended to rate this capacitor appropriately due to the voltage.

    Correction on the ratings above but C_INP is rated for 100V and C_INN is rated for 50V (C10 and C11 respectively).

    If the application requires a short distance 200Vp is a really large voltage which can help you a achieve a large distance. Keep in mind the larger the voltage is the larger your settling time which in turn reduces your minimum possible measurements due to ringing. 

    I hope this helps!

    Best,

    Isaac