• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 81 subscribers
  • Views 841 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMS320F28379D: maximum Hysteresis of comparator

Strong ZHANG
Expert 4720 points

Part Number: TMS320F28379D

In Table 5-54 of SPRS880G list the maximum value of Hysteresis of comparator is 48 CMPSS DAC LSB, if want to set the Hysteresis value to 200mV, is it possible to achieve that?

  • 0
    TI__Mastermind 28275 points

    Hi Zhang,

    The comparator in the F28379 uses the compdac to apply the hysteresis which is why the units is in cmpss dac lsb. Since the compdac uses vdda or vdac as reference voltage, the maximum hysteresis that can be applied is around 42mV (lsb to mV).

    Out of curiosity, is there a reason you need 200mV of hysteresis? If your system has that much noise, you should consider reducing the noise in the system instead.

  • 0
    TI__Guru 62975 points
    Strong,

    If more hysteresis is required, you might consider adding an external resistor network to supplement or substitute the internal hysteresis: en.wikipedia.org/.../Schmitt_trigger

    -Tommy
  • 0 in reply to tlee
    TI__Expert 4720 points
    Tommy,

    Thanks, It is customer's requirement that they need 200mV of hysteresis, they use the ADC channel for comparator as well as AD sample, as I did not find the parameters of internal resistor network, Could you help to explain how to add an external resistor network when need more hysteresis ?
  • 0 in reply to Strong ZHANG
    TI__Guru 62975 points

    Strong,

    Are you able to see the link?  There's a generic topology and formula for calculating the hysteresis.

    It's essentially a pull resistor that allows the comparator GPIO output to bias the input voltage.

    -Tommy