SN74ALVCH16373: Input overshoot max?

Scott Asher

Part Number: SN74ALVCH16373

Hello, I have some questions regarding input overshoot max on SN74ALVCH16373. The datasheet just has absolute max rating of Vi = Vcc+0.5V. But I assume this is a DC spec and not a dynamic overshoot spec. When simulating at the die with the IBIS model, I am seeing it go above VCC+0.5V for about 0.5ns, and the peak is about VCC+0.87V. Simulating at the pin it goes above VCC+0.5V for about 0.5ns but the peak is reduced to VCC+0.73V. In all cases it is less than 4.6V max spec.

Is this overshoot acceptable for this short a time and peak? There is no iIK spec for going above VCC+0.5V like there is for Vi < 0.

For Vi < 0, the simulation at the die shows it going below -0.5V for about 0.507ns and the peak is about -1.11V, but the input current is about -21mA but I assume this is OK since it is less than iIK = -50mA. Is this overshoot below -0.5V OK?

Thanks,

Scott

over 6 years ago

0 Emrys Maier over 6 years ago

TI__Guru* 96591 points

Hi Scott,
There is a diode to Vcc on the input of this device, so a short spike above Vcc won't cause a problem. The delay in the model is likely the time for the diode to turn on. As long as you don't exceed the absolute max for the device (4.6V) then it won't hurt anything.

0 Scott Asher over 6 years ago in reply to Emrys Maier

Intellectual 500 points

Hi Emrys,

Thanks for the response! I have some follow-up questions. The datasheet just mentions iIK (input clamp current) for Vi < 0. Does not mention iIK for Vi > VCC, which indicates to me that there is only a diode from input to ground and not to VCC. Is the datasheet incorrect or not complete? Is there an iIK spec for Vi > VCC as well?

Thanks again!

Scott

0 Clemens Ladisch over 6 years ago in reply to Scott Asher

Guru 243110 points

Quite a few datasheets hace inconsistencies like that.

The ALVC family does not have overvoltage-tolerant inputs, so there is an ESD protection diode to VCC, so any specifications that imply the lack of such a diode are wrong.

0 Emrys Maier over 6 years ago in reply to Clemens Ladisch

TI__Guru* 96591 points

Yes - just to back Clemens up here, I checked the design documentation. There is definitely a diode to Vcc (it's part of the bus-hold latch on the inputs). The datasheet needs to be fixed.

0 Scott Asher over 6 years ago in reply to Emrys Maier

Intellectual 500 points

Hello and thanks for the response!

I have another follow-up question on this. For the case when going above VCC + 0.5V, is there an iIK max spec for the VCC clamp diode like there is for the ground clamp? Is it 50mA max as well?

Thanks again!

Scott

0 Emrys Maier over 6 years ago in reply to Scott Asher

TI__Guru* 96591 points

It's unlikely that you would be able to get 50mA to go through the diode - because of the latch design, there's a 1kohm resistor in series with the diode. As long as you stay below the absolute max, everything will be fine.

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SN74ALVCH16373: Input overshoot max?