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BOOSTXL-TUSS4470: BOOSTXL-TUSS4470 with Transformer

Pejman Hashemi
Prodigy 20 points
Part Number: BOOSTXL-TUSS4470
Other Parts Discussed in Thread: TUSS4440, TUSS4470

Tool/software:

Hi, 

I am using BOOSTXL-TUSS4470 and want to increase output current on Transducer. I am a bit confused. 

On the Schematics of BOOSTXL-TUSS4470, After OUTA and OUTB, there are three options which can be selected by resistors. 

Option one is directly drive the Ultrasound transducer which is the default. 

Option two is connecting to the Gate of the Mosfet. But the source of the Mosfet is connected to the input of the transformer. 

Option three is connecting directly to the transformer. 

First of all, can we drive the transformer with TUSS4470, or it can only be able to drive by TUSS4440?

Secondly, what is the purpose of the Mosfet before the transformer?

Can we use only Mosfet to add more current without the transformer?

Thanks, 

Pejman

  • 0
    TI__Mastermind 23045 points

    Hello Pejman,

    The TUSS4470 cannot be used to directly drive a transformer the option is mainly there because the TUSS4440 and TUSS4470 share the same EVM. 

    The purpose of the FETs before the transformer is to use the TUSS4470 in the PRE_DRIVER_MODE, where you have the need to driver a higher current or voltage into the primary side of the transformer.

    If you mainly need to add more current and not much more voltage then it should be possible to use just a mosfet without the need of the transformer. You may be able to test this on the EVM by using changing R4-R10 to the appropriate configuration for pre-driver mode. You would need to connect the transducer to the OUTx_XF path to see if this helps you achieve the current.

    Best,

    Isaac

  • 0 in reply to Isaac Lara
    Prodigy 20 points

    Thanks for quick reply Isaac. 

    So, my understanding is we can NOT drive a transformer directly with TUSS4470, but we can drive the transformer with TUSS4470 if we use mosfet before transformer and set the register PRE_DRIVER_MODE of the TUSS4470 to 1. Is my understanding correct?

    Also, we can drive the transducer with pre-driver mosfets. We need to remove the default R4 and R8 and connect the R7and R10 which are connecting the the Gate of the mosfet. Then connect the OUTx_XF to the transducer. Is my understanding correct?

    Moreover, the max Vgs of the mosfets on the dev board are 10V. It means we need to set VDRV below 10V to make sure is not exceeding the Vgs of the mosfet. Is that right?

    Generally, we are using the ultrasounds on the 10 meter distance. They are working perfectly. However, we want to use them on the 20 meter application and they are not as reliable as 10 meters and sometimes can not measure the TOF. We have increased the drive voltage to FF which is 15V+5V and we can increased the  number of pulses to 16. Is there any other methods we can change to work with 20 meters without using mosfet or transducer?

  • 0 in reply to Pejman Hashemi
    TI__Mastermind 23045 points

    Hello Pejman, 

    Thanks for the background on this.

    1. So, my understanding is we can NOT drive a transformer directly with TUSS4470, but we can drive the transformer with TUSS4470 if we use mosfet before transformer and set the register PRE_DRIVER_MODE of the TUSS4470 to 1. Is my understanding correct?
      1. Your understanding is correct. 
    2. Also, we can drive the transducer with pre-driver mosfets. We need to remove the default R4 and R8 and connect the R7and R10 which are connecting the the Gate of the mosfet. Then connect the OUTx_XF to the transducer. Is my understanding correct?
      1. I was reviewing this option on the evaluation module and it looks like this option would not be viable. Mainly because we would need to move some connections for the OUTA_XF, OUTB_XF and GND to different connections in order to be able to drive a transducer properly so while this would be an option on a customer board it is not an option on this board.
    3. Moreover, the max Vgs of the mosfets on the dev board are 10V. It means we need to set VDRV below 10V to make sure is not exceeding the Vgs of the mosfet. Is that right?
      1. Correct, you would want ensure that that the VDRV does not exceed the Vgs spec of the FET.
    4. The jump from 10m to 20m is pretty large so I can see how increasing the driving voltage by just 5V might not be able to achieve the performance you are looking for in the system. Increase the pulses does help increase the SPF generated, have you tried further increasing the number of emitted pulses to see if this starts to get more consistent? Increasing the voltage may be another option if you are able to increase your voltage.

    Best,

    Isaac

  • 0 in reply to Isaac Lara
    Prodigy 20 points

    Hi Isaac, 

    Thanks. I am developing the schematics at the moment. So I can modify the dev board connection on my board. Generally if we connect the OUTA and OUTB to the gate of the mosfets and then connect the source of the mosfets to the transducer connector, we can drive the transducer with mosfets or any other circuit change required?

  • 0 in reply to Pejman Hashemi
    TI__Mastermind 23045 points

    Hello Pejman,

    Simply connecting the transducer to the source of the FET would not yield what you would need it to. The transducer would need to be connected to connect to either the source or the drain of the MOSFET and this type of topology can sometimes require both a p and n ch MOSFET. It mostly depends on what your transducer requires. 

    Best,

    Isaac