TLC6C598: Allowable undershoot values

Hello Ryu,

Are you referring to output drain voltage undershoot? I see the rise(tr) and fall(tf) time are noted as 210ns and 128ns respectively. This is time to reach 90% or 10% of the expected voltage during a transition. Is the undershoot during this period?

Could you be more specific on which signal or show the waveform? I don't have specific information on voltage undershooting but it can be sampled on an EVM if needed.

For typical switching waveforms see the images below:




Best,
Isaiah

Hi Isaiah,

Thank you for your reply.
I'm Ryu's colleague.

Sorry for luck of information.

This is for 8pin(/G).
This undershoot is exceed to absolute maximum voltage.
But it was short time (20ns).

I'd like to know if there's any problem even for a short time.

BR,
Kengo.

Hi Kengo,

Thank you for the additional information. I am still a little confused what you mean by voltage undershoot exceeding absolute maximum rating. Is there an overshoot from the low to high transition as well?

There is no specific max rating listed for /G pin but it should not be greater than VCC. Is the pin is reaching the correct high/low thresholds to disable/enable the output? 

Could you provide a scope waveform showing your concern?

Best,
Isaiah

Hi Isaiah,

Is /G logic input, right?


If there are no regulations, please let me know.



BR,
Kengo.

Hello Kengo,

Yes, /G would be a logic input with -0.3-8V input range. I see the undershoot is reaching -0.43V but as the timing is much shorter than the propagation delay time, I am not as concerned. Is the output reflecting enable/disable from /G pin accurately? Is an MCU being used to toggle the /G pin?

I will sample this on a similar EVM and compare the waveforms.

Best,
Isaiah

Hi Isaiah,

My concern is whether it will fail due to this undershoot exceeding the absolute maximum rating.
What do you think about broken?

BR,
Kengo.

Hi Kengo, 

I see your concern, it is best to reduce the undershoot to be within the pin voltage range to avoid damage over time. Could you provide a schematic? Perhaps placing a series resistor with the MCU or a clamp diode at the G pin can correct this. 

Was the undershoot measured with a tip and barrel probe? 

Best,
Isaiah 

Hi Isaiah,

Thank you for your reply.
What we want to know is how many seconds beyond the absolute maximum rating will cause destruction.
Please clearly specify whether exceeding the absolute maximum ratings within the propagation delay time will only affect the service life without causing failure, or whether even momentary exceedances are unacceptable.

For example, please tell me how many seconds is acceptable.
Alternatively, please provide information indicating that the absolute maximum voltage rating may be exceeded at this level of current.
Some devices include this information as a note.

Best Regards,
Ryu.