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AM26C31: Chattering Issue

CHO SR
Genius 3415 points
Part Number: AM26C31
Other Parts Discussed in Thread: AM26LS31

Hi,

The customer has a chattering issue.

Occurs when power is off when Pulse In and Pulse Out (+) measurements are made.

When Pulse In is off (3.3V level) and the level is gradually reduced to about 1.3V, chattering phenomenon at Pulse Out (+) like a red box.

If you check the figure on the left, only Pulse In is measured without chattering.

This means that the Pulse Out (+) chattering phenomenon noise appears to be loaded on Pulse In measurements as well.

Vcc applied 5V and drops to Low after chattering occurs.

The AM26C31 datasheet has a minimum High Level input voltage of 2 volts and a maximum Low Level voltage of 0.8 volts.

If the level value between 0.8V and 2V is slowly entered, can chattering occur?

Chattering does not occur when measured by applying AM26LS31.

Chattering does not occur when measured by applying AM26LS31.

What is the difference between AM26LS31 and AM26C31 in terms of chattering occurrence?

Please give me some advice to solve the chatter issue.

  • 0
    TI__Guru 74292 points

    Cho,

    An engineer has been notified of this post and will reply by the end of business CST.

    Regards,

    Eric Hackett

  • 0
    TI__Guru 52462 points

    Hi Cho,

    Are the tests being performed with VCC = 0V? If so the device is not meant to work correctly without power.

    If there is power - how fast is in the input transition time - the logic state is undefined between 0.8V to 2V - if the input signal sits in that range too long supply current can increase and potentially oscillate - its not spec'd because its not generally an issue unless the system is intentionally slowing down the input transition signal which is not advisable. 

    This is not something we spec - so there is no recorded in how this functions between the two devices. There could be a difference based on difference in structure  - but it isn't something that is spec'd.

    Please clarify if you are testing at VCC = 0V  and the input transition time. 

    Best,

    Parker Dodson