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TL494: Tailored Dead Time

Andres Miguel Machara Chomiak
Prodigy 50 points

Part Number: TL494

Hello,

In the "Designing Switching Voltage Regulators With theTL494" document, says the following: 

"...the TL494 can be tailored to the specific power transistor switches that are used to ensure that the output transistors never experience a common on time. The bias circuit for the basic function is shown in Figure 29. The dead-time control can be used for many other control signals."

My question is related to the formulas showed above:

*TD abbreviation is not defined in the document. I Think that TD means the Dead-period, is'n it? In souch case, is the result of this formula the maximun dead period in the Q1 and Q2 transistors regarding the R2 value?

*External resistors R1 and R2 never should be more than 5Kohm?

Thanks in advance!

  • 0
    TI__Expert 7900 points

    Hello Andres,

    TD is the dead-time in seconds, not the period.  TD is the off-time between external transistors at maximum duty cycle.  For example, with R2=0 ohms, the dead time is 5% (0.05) of Rt*Ct.  Introducing R2 increases the dead-time.  R1 and R2 must sum to 5kohms.  After choosing an R2 value (in kohms), the value of R1 = 5k - R2.

    Regards,

    Eric