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UCC27282: UCC27282

Ben Rowley
Prodigy 10 points
Part Number: UCC27282

Tool/software:

I am driving four UCC27282DRCT chips with one 24mA drive 74AUP2G3404GW,125 with four 1000pF caps distributed close to pins for noise. I am seeing insufficient drive strength on the enable line. Something is pulling the signal down below the VEN threshold. My question is, what is the current requirement for each of the four enabled inputs? The second question would be, why does changing the HIN and LIN impact the enable input?

  • 0
    TI__Intellectual 1340 points

    Hi Ben,

    Thanks for reaching out to TI.

    I have a couple of questions/comments here:

    1. Are you tying VDD to the enable or are you switching it?
    2. Is this replicable with only one UCC27282 device?
    3. Typically, a 1nF cap is not sufficient for this device. Can you try increasing it to 0.1uF and adding another 1uF cap in parallel?

    Please let us know if this works.

    Jeremiah

  • 0 in reply to Jeremiah Vo
    Prodigy 10 points

    Hi Jeremiah,

    Thank you for the assistance! 

    Question 1: We are switching the enable; hence, the high-current driver provides the fanout necessary for four H-bridge drivers. The enable is used to prevent a thermal runaway when a second processor detects an out-of-bounds condition and is not switched during the normal cycling of the Peltier devices.

    Question 2: I am unsure how to answer this question specifically, so I will provide more information. We have built a couple hundred boards with the TI solution and more with the Diodes solution. We switched because we could not find the reason for a 20% failure rate in the Enable circuit. We want to solve this issue and use the TI component. The data we collected suggests a failure in a single driver of the four causes voltage reduction on the enable, which further reduces voltage when HIN or LIN is active to a state below the disable threshold. We did not understand how, compared to the block diagram, the signal is influenced by the other input signals. We can replace the driver, and the circuit will work for a time, but it had a high failure rate in the future for that specific board. We have not found a root cause or difference between the PCBs or the supporting components to explain the difference in the other working 80% of the boards with TI drivers.

    Question 3: I think there is a misunderstanding about the 1nF cap. It is only used on the enable circuit to prevent noise from influencing the enable signal. For the power delivery bypass and decoupling of each driver, we have  2,2uF, 0.1uF, and 1nF. This is separate from the enable signal conditioning. 

    I am leary of sending schematics on an open forum, or I would have sent the schematic.

    Thanks,

    Ben

  • 0 in reply to Ben Rowley
    TI__Intellectual 1340 points

    Hey Ben,

    Noted on the schematic comment, but would you be able to send us a waveform of the enable pin under two conditions:

    • Normal operation
    • Problematic operation

    Additionally, you mentioned a Diodes device, which device is this and you've not seen any resemblance of the problem using that Diodes device?

    Thanks,

    Jeremiah