SN74AHCT1G125: Penetration Current

Kuramochi Tadahiko

Guru 28715 points

Part Number: SN74AHCT1G125
Other Parts Discussed in Thread: SN74LVC1G17

Hi,

Is there any possibility that penetration current is flown when the input pin is opened?

Best Regards,

Kuramochi

over 4 years ago

0 Dylan Hubbard over 4 years ago

TI__Mastermind 45725 points

Hey Kuramochi,

I'm not sure if I follow the question exactly, but if the input is left open then you will have a floating node and this can cause an increase in supply current.

0 Kuramochi Tadahiko over 4 years ago in reply to Dylan Hubbard

Guru 28715 points

Dylan-san,

Thank you for your help.

My customer says that the competitor device flows penetrating current when input pins are opened.

Does it mean that SN74AHCT1G125 is taken measures for penetrating current?

Best Regards,

Kuramochi

0 Clemens Ladisch over 4 years ago in reply to Kuramochi Tadahiko

Guru 316690 points

I guess the proper term is "shoot-through current".

TI devices behave in the same way: [FAQ] How does a slow or floating input affect a CMOS device?

The simplest way to avoid a floating voltage at the input would be to add a weak pull-down or pull-up resistor.

0 Kuramochi Tadahiko over 4 years ago in reply to Clemens Ladisch

Guru 28715 points

Clemens-san,

Thank you for your help.

Is the device damaged by this shoot-through current?

Best Regards,

Kuramohi

0 Clemens Ladisch over 4 years ago in reply to Kuramochi Tadahiko

Guru 316690 points

If the voltage is near the switching threshold, oscillations can happen. Those are more dangerous, and possibly damaging.

Devices with Schmitt-trigger inputs (e.g., SN74LVC1G17) will not be damaged by floating inputs. They have no oscillations, but they still have shoot-through currents.

0 Kuramochi Tadahiko over 4 years ago in reply to Clemens Ladisch

Guru 28715 points

Hi Clemens-san,

Thank you for your help.

Does the shoot-through occur when the device is disabled (/OE=H)?

Best Regards,

Kuramochi

0 Clemens Ladisch over 4 years ago in reply to Kuramochi Tadahiko

Guru 316690 points

The OE pin disables the output. The input always stays active while the device is powered.

Logic

Logic forum

SN74AHCT1G125: Penetration Current