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TPA3111D1 evaluation module (TPA3111D1EVM) used for solenoid currents

John Sigman
Prodigy 65 points
Other Parts Discussed in Thread: TPA3111D1EVM, TPA3111D1, TPA3116D2, TPA3118D2
I want to know if I can use the TPA3111D1 evaluation module (TPA3111D1EVM), to amplify currents in an inductive coil load.
 
At low frequencies, this load will look like a short.
 
I see that the device has short-circuit protection, but will it be able to amplify the signal in a current?
 
Additionally, I would like to know if it can amplify signal up to 100 kHz.
 
I don't see why this wouldn't be feasible.
 
The maximum frequency given is 20 kHz but that likely has to do with the upper limit on human hearing, and not a technical limitation of the device.
  • 0
    Prodigy 65 points
    Same problem, but slightly different questions now.
    It seems that the frequency range isn't a problem for us. This part will work even with the phase distortion at 100 kHz.
    The short-circuit protection is a problem, it looks like. Is there a way to disable this? We would be connecting a load of about 1 Ohm DC and 1.5 mH. Would this register as a short? We don't really need to amplify "power", we're trying to build a magnetic field via a loop, so it's only generating high currents that we want, not power.

    If there is no way around the short-circuit protection, is there another part that would meet these needs?

    Thanks
  • 0 in reply to John Sigman
    Prodigy 65 points
    Actually, it's more like 2.5 ohms DC
  • 0 in reply to John Sigman
    TI__Genius 9175 points
    Hi John,

    The issue here is that high currents causes the output stage of the amplifier to heat up rapidly due to the RDS-on of the FETs. This in turns increases the RDS-on and makes the problem worse. This is why we specify the minimum load of 3.2ohms and add the short current protection.

    Since this device does not have over current protection, just short circuit current protection, the specific current to trigger the trip point needs to be tested with your specific loading. For this test, you cannot use steady stage signals since this will burn up the part and cause over temp. Instead use a burst waveform to keep the part cool and observe the peak current into the load before OC shutdown.

    If you plan to use and LC filter with this device, this will further complicate things since your pole needs to be set beyond 100KHz. This will make passing EMI a bit difficult.

    Take a look at the TPA3118D2 and TPA3116D2 these are stereo parts that can be strapped together in mono for twice the current drive. The TPA3118D2 will have a peak current of 15A in PBTL mode before OC, however don't expect 15A continuous!! This is well over the power specs of this device. I recently tested this and with a 1ohm load and 15A peaks can be driven cleanly in a burst signal mode. Remember that power supply voltage and given load impedance will determine the maximum current you can swing. You cannot get 15A peaks into higher load impedances.

    Best Regards,
    Matt
  • 0 in reply to Matthew Beardsworth
    Prodigy 65 points

    Been testing the TPA3111D1EVM, and haven't been able to get a test signal running through it.

    It should be as simple as connecting a power supply between 8 and 26 V and adding the signal to the input?

    It looks like asserting the shutdown pin should be handled automatically, but when I connect the power supply, SD and FAULT are both at about 30 mV, instead of tied high.

    I'm also no longer worried about my load being considered a short circuit, if anything it will be a much higher impedance than 8 ohms, but the device should be able to handle that, just at reduced power.

    Thanks

  • 0 in reply to John Sigman
    TI__Genius 9175 points

    The EVM should be very straight forward to get running. Have you taken a look at the user’s guide HERE?

    If using the output from the Out + and Out – banana jacks, JP3 and JP4 must be installed. If you remove jumper JP1, Fault and SD will be independent. With JP1 removed check the voltage on Fault and SD after cycling SD. If Fault is low and SD is high, the fault pin is pulling SD low. There may be a short or DC offset issue at the output. Make sure the load is floating with respect to ground and that there are no shorts between OUT + and GND and OUT – and GND.

    Also try this with the load disconnected.


    Regards,

    Matt

  • 0 in reply to Matthew Beardsworth
    Prodigy 65 points
    A very simple test:
    20 V connected to GND and PVCC.
    JP1 disconnected, every other jumper connected. No input signal connected. I get high voltage on SD_bar and low on FAULT_bar... Cycling SD by S1 has no effect on FAULT_bar. It is the same result with an open load as it is with a 50 uH inductor across the OUT+ and OUT- banana clip ports.

    What is going on here? I have extra components of this chip, should I swap one of them in? I don't see how this one could be bad yet.
    Thanks for the help
  • 0 in reply to John Sigman
    TI__Genius 9175 points

    John,

    It sounds like a short somewhere on your board. Have you done a continuity check with a multimeter to make sure there are no shorts between any two output pins and between the output pins and ground?

    If you cant find any shorts, it may make sense to swap the device if you have extras on hand.

    Sorry for the inconvenience.

    Matt

  • 0 in reply to Matthew Beardsworth
    Prodigy 65 points
    hey Matt,
    We couldn't find any shorts on the board. When we replaced the part, had the same problem. Then we went again and ordered another eval board, same setup. It shows the same error. Are you sure this is the right way to check if the hardware is working?

    Again, all I'm doing is:
    -Nothing connected between the output banana connectors.
    -+18 V connected between PVCC and GND banana connectors.
    -JP1 disconnected, all others connected.

    I get a low voltage on FAULT_bar and a high voltage on SD_bar, indicating that there is a fault even in this bare-bones configuration. Doesn't seem to be related to a bad chip, since it has been the same thing on two identical boards.

    Thanks again,
    Johnny
  • 0 in reply to John Sigman
    TI__Genius 9175 points
    Hi John,

    My mistake... with JP1 Removed, Fault will be low since this jumper acts as a pull-up. However if even with JP1 removed the part should still function if there is no fault.

    Try inserting JP1 with your new board. If there is an issue, both SD and Fault will be low as you found with the previous board (which I believe had a short). Fault will then cycle in attempt to self clear the issue since SD and Fault are tied together via JP1.

    With the JP1 jumper installed, if both SD and Fault are high, the device is active.

    I just tested the fault on the EVM by shorting one of the output legs to ground while playing a test tone. Everything worked as outlined above.

    Best Regards,
    Matt