SN74LVC8T245: collide with two outputs

user3581705

Prodigy 30 points

Part Number: SN74LVC8T245

If two different SN74LVC8T245s collide with two outputs, will they break down?

The same signal is connected to the input.

DIR and OE are GND connections.

VCCA = 3.3V and VCCB = 5V are connected.

It's good if the current flows only momentarily,

I hope it doesn't damage the device.

Thank you.

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 243180 points

At 3.3 V, shorting two LVC outputs will result in a current of about ±80 mA:

The absolute maximum rating of ±50 mA must not be exceeded, not even for a short time. Degradation or permanent damage is possible.

0 Emrys Maier over 2 years ago

TI__Guru* 96591 points

Hello,

user3581705 said:
The same signal is connected to the input.

As long as the two outputs have extremely similar waveforms (within ~1ns), then you can have two channels of buffer driving the same line. This is generally not a good idea though because it's very difficult to get that timing right with two separate devices, and if the two are driving different levels, then what Clemens mentioned will happen and the excessive current can cause damage to the device.

If you are referring to two channels of the same device in parallel, then this is something that can be done. We even have an FAQ with recommendations on that: [FAQ] Can I connect two outputs from a CMOS logic device together directly? - Logic forum - Logic - TI E2E support forums