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CC2533: Regarding CC253x Interrupt falling edge detecting level..

Ernest Cho
Intellectual 2961 points
Part Number: CC2533

Hello Champs,

One question popped up from customer side, regarding CC2533 Interrupt edge detection voltage level..

Customer application have tilt sensor(analog level) and it is connected to I/O port interrupt in CC2533 and detect falling interrupt.
They supplied 3.3V at VDD and I/O for tilt sensor levels are changing from 0 to VDD. (sometimes it moves very slowly).

But when the level is slowly going down, the interrupt is detecting around 2~1.5V.
And what customer want to know is .. what level would be the interrupt detection points when VDD become lower as like 2.xV?
Please advise me if you have any ideas. Thanks.

ps) Some discussion regarding VIH and VIL level when VDD<2.6V at below link, but it is level itself, not for interrupt edge detection level.

https://e2e.ti.com/support/wireless_connectivity/zigbee_6lowpan_802-15-4_mac/int_zigbee_6lowpan_802-15-4_mac/f/961/t/244195

Regards,
Ernest Cho

  • 0
    TI__Expert 6315 points

    Hi Ernest,

    VIH and VIL gives you the border limits across all devices. Per single device, per pin, the crossover lies at one point in that range. This threshold should not be used as an accurate threshold for a falling voltage, unless that threshold is characterized per device across voltage and temperature. It is intended for digital/logical detection. On most devices the crossover is close to VDD/2.

  • 0 in reply to Torbjorn Sorby
    TI__Intellectual 2961 points
    Hi Torbjorn,
    Thank you for your reply. Your comments make sense.
    But one more question for this discussion.
    The interrupt crossover threshold (Interrupt detection) voltage should need schmitt trigger, am I right? (Otherwise it could continuoulsy get the interrupt signal in a certain level)
    And CC253x should have schmitt trigger for the interrupt edge detection, but what voltage(+- ??mV) would be for?
    Thanks.
    Ernest Cho
  • 0 in reply to Ernest Cho
    TI__Expert 6315 points
    I don't know the details, but yes each pad has a Schmidt trigger. Here's a comment from designer:
    "...
    Regarding pin interrupt detection there is one detector per pad. The signal from the pad is either inverted or not (corresponding to the selection for rising/falling edge). This signal goes to the clock input of a flop which is the interrupt detector – hence only a transition from low to high or from high to low can be detected.
    ..."