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About the Enable timing of TPS74801 (CR-time constant)

Satoshi
Guru 19645 points
Other Parts Discussed in Thread: TPS74801

Client is going to delay the Enable_ON timing of TPS74801 by CR.

If Enable startup is too slow, does the Floating(ex,0.4V～1.1V)  time of EN_ON/OFF become long and cause trouble in operation?

Is it necessary to set time(ms) to below fixed?

(I think that OK with not the recommendation range but generalizations)

 

Now, the client is considered by C= 1.5μF and R=270kΩ. (400ms delay)

Best regards,

Satoshi

  • 0
    TI__Guru 55940 points

    Hi Satoshi,

    TPS74801 was designed to be compatible with slowly ramping signals.  The hysteresis and deglitching were added to accommodate slow ramp signals.  This is described in more detail in the Enable/shutdown section of the datasheet.

     The typical enable threshold is 0.8V but this threshold varies with temperature.  The customer should be aware that the device will enable before 1.1V.  If timing is critical for the application, you may want to look into using a voltage supervisor with a 400ms delay. 

    Very Respectfully,

    Ryan