SN74HCS86: Why the IIK spec is different between sn74hcs86 and sn74lvc86A?

Eggsy Pang

Part Number: SN74HCS86
Other Parts Discussed in Thread: SN74LVC86A,

Hi Team,

Compared with sn74hcs86 and sn74lvc86A datasheet, I saw IIK support +/-20 mA (when VI < –0.5 V or VI > VCC + 0.5 V) in sn74hcs86 datasheet.

But sn74lvc86A just support -50mA rather than +/-50mA.

Why doesn't sn74lvc86A support +50mA?

And sn74AHC86A also just support -20mA rather than+/-20 mA.

Do you have any suggestions?

Thanks!

over 3 years ago

0 Clemens Ladisch over 3 years ago

Guru 242810 points

LVC and AHC family devices do not have positive clamping diodes. This allows input voltages higher than V_CC, but means that the absolute maximum rating must not be exceeded under any circumstances. See [FAQ] Can the input voltage (Vi) to my logic device be higher than the supply voltage (Vcc)?

0 Eggsy Pang over 3 years ago in reply to Clemens Ladisch

TI__Expert 4985 points

Hi Clemens,

VC and AHC family devices do not have positive clamping diodes, why do they support input voltages higher than VCC?

One more question, if VCC =3.3.V, sn74hcs86 High-level input=2.5V, is it ok?

We can't find the VCC =3.3.V, High-level input range in the datasheet?

0 Clemens Ladisch over 3 years ago in reply to Eggsy Pang

Guru 242810 points

With a positive clamping diode, higher voltages require a current-limiting resistor, and that current will flow into V_CC and might power the device. Without a positive clamping diode, no current flows, and a voltage can be applied even when the device is powered off.

For 3.3 V characteristics, see [FAQ] What method is best used for estimating specification values between those given in the datasheet?

0 Eggsy Pang over 3 years ago in reply to Clemens Ladisch

TI__Expert 4985 points

Hi Clemens,

So as for With a positive clamping diode and Without a positive clamping diode, which one is stable and robust?

Thanks!

0 Clemens Ladisch over 3 years ago in reply to Eggsy Pang

Guru 242810 points

Both are, depending on circumstances.

Logic

Logic forum

SN74HCS86: Why the IIK spec is different between sn74hcs86 and sn74lvc86A?