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UCC21222-Q1: Is there problem if we use DT pin as open?

Yoshiki Ochi
Genius 9365 points
Part Number: UCC21222-Q1

Hi team, 

Is it OK to use UCC21222-Q1 with DT pin open?
Datasheet says "Tying DT to VCCI or leaving DT open allows the outputs to overlap". If PWM controller has enough deadtime, is it OK to make this pin open?

Reagrds,
Ochi

  • 0
    TI__Genius 10652 points

    Ochi-san,

    Yoshiki Ochi said:
    "Tying DT to VCCI or leaving DT open allows the outputs to overlap". If PWM controller has enough deadtime, is it OK to make this pin open?

    ,

    If you inforce the deadtime in the controller, then leaving DT floating or tie to VCC will be fine.

    Best

    DImitri

  • 0 in reply to dimitri james
    TI__Intellectual 2061 points

    Thanks Dimitri,

    Hi Ochi-san,

    If DT is not used, please tie the DT pin to VCCI. High voltage noise coupled into DT pin may cause driver malfunction.

    Thanks.

  • 0 in reply to Wei Zhang
    TI__Genius 9365 points

    Hi Zhang, 

    Thank you for your additional reply.

    Do you mean that to keep DT pin open is not suitable for high voltage noise issue and we have to tie DT pin to VCCI?

    Regards,
    Ochi

  • 0 in reply to Yoshiki Ochi
    TI__Guru**** 189401 points

    Hi, Ochi-san,

    Your understanding is correct; we do not recommend leaving the DT pin open as it can pick up noise. You can either tie it to VCCI, or put a 2.2 nF cap to ground as recommended in the Pin Function Table description in the datasheet:

    Tying DT to VCCI or leaving DT open allows the outputs to overlap. Placing a resistor (RDT) between DT and GND adjusts dead time according to the equation: DT (in ns) = 10 × RDT (in kΩ). TI recommends bypassing this pin with a ceramic capacitor, 2.2 nF or greater, to achieve better noise immunity. Place this capacitor and RDT close to the DT pin.