SN74LVC244A: high output direct connect to GND

eric wang

Part Number: SN74LVC244A

Hello TI Experts,

We have a faulty design (which have already been mass shipped out in field ….), we want to evaluate the risk of the design and consider next step

Conditions:
1. SN74LVC244APWR

3.3V power supply
Two not used high output GATEs (input is PU) are directly connect to GND (bad design)
All the other remaining Gates have very small current consumption, less than 1mA

As the following picture:

Questions:

What is the consequence? Will this damage the whole chip or only that two gate? We can accept if only that two gates are damaged as they do not carry any function

Thanks

Eric Wang

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 244020 points

Figure 15 of Input and Output Characteristics of Digital Integrated Circuits at 3.3-V Supply Voltage shows that the output current will exceed 80 mA, per pin. This violates the absolute maximum ratings for the output current and for the V_CC current, is very likely to damage these outputs, and might damage other parts of the chip.

0 eric wang over 1 year ago in reply to Clemens Ladisch

Prodigy 70 points

Hello Sir,

Thanks for the scientific explanation, but please allow me to ask how the 80mA value is carried out from the curve, I just feel difficult to understand the curve………...

Also is it true there is no any OC(over current) protection for the port?

Thanks

Eric Wang

+1 Clemens Ladisch over 1 year ago in reply to eric wang

Guru 244020 points

This graph shows the current that results when the output is forced to a specific voltage. The two curves are for the output driving high or low. Positive current is the output sourcing current; negative, sinking current.

Normal operation is at 3.3 V for small positive currents, and at 0 V for small negative currents. Everything else violates the allowed limits.

Logic

Logic forum

SN74LVC244A: high output direct connect to GND