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Original question:

PGA460-Q1: PGA460-Q1 Multiplexing in Half-Bridge Driver Mode for Mono-static or Bi-static Transducers

PGA460-Q1: PGA460-Q1:

Guilherme Carlos
Prodigy 30 points
Part Number: PGA460-Q1
Other Parts Discussed in Thread: PGA460, DRV8870, MUX36S08

I am facing the challenge of designing a circuit using PGA460 to drive 8 ultrasonic transducers. The point is that the transducers I want to use are closed top and I need to have long distance measurements and PGA's datasheet says that transformer driving solutions are adequate for this situations.

So to reduce costs I thought of using a multiplexer to drive the 8 transducers with only one PGA460, I have already seen solutions in this forum but only with direct driven method. So is it possible to use the transformer option with muxes? how can I select the appropriate mux?

Thanks for the attention!

  • 0
    TI__Mastermind 27910 points
    Hi Carlos,

    Currently, we do not offer a solution to mux multiple transformer driven solutions. This is mainly due to the either high-current requirement (upwards of 500mA) at the primary of the transformer, or the high-voltage excitation voltage (+/-100V) requirement at the secondary of the transformer.

    Given the required components are available, you may be able to build a discrete high-current or high-voltage mux system at lower cost than eight independent PGA460 modules. Perhaps a full-bridge direct-drive muxing solution will be easier to implement due to the low sink current requirement of sub-50mA, while still offering comparable performance to a transformer driver.
  • 0 in reply to Akeem Whitehead
    Prodigy 30 points
    I have checked the proposed solution using the full-bridge direct-drive, and that raised me another 2 questions.

    1- Since I am designing an automotive application, I have 12V from the batteries available. Therefore I will have to use a step-up converter to get something around 40V to drive the DRV8870. My question is what would be the current requirements of the step-up converter?

    2- I haven't found any project using the muxing full-bridge, so I don't really know if the MUX36S08 (suggested by you on another thread for the muxing half-bridge direct-drive solution) would be adequate. If not, what are the requesites I have to check for selecting the appropriate mux?

    Thanks so much for all the help!
  • 0 in reply to Guilherme Carlos
    TI__Mastermind 27910 points
    Carlos,

    1. If you were to tie the full-bridge high-side directly to battery to generate 24Vpp at the transducer, your maximum detectable range for an ISO-pole (1m height, 7.5cm diameter) will be about 3m. Depedning on your range requirement, you may not need to maximize the DRV8870 reference to 40V, but if you do to generate 80Vpp at the transducer, your maximum range increases to about 4.5m. The transducer only needs to sink 50mA during excitation, so you can set your step-up converter output current to at least ~100mA for additional margin.

    2. Your full-bridge mux/switch must be able to support the intended excitation voltage requirement (i.e. +/-40V), and (depending on how you current limit the driver source) at least 100mA of mux/switch current. The DRVxxxx series is intended for motor driver applications, so they are rated for Amps of driver current, which is more than enough for a transducer's typical mA requirement.