SN65HVD1792-EP: What reason for restriceted operating air temp., Ta to +105deg.C

Hi Nakashima-san,

The limitation is due to the fact that this device failed to maintain specification compliance and could suffer damage when ambient was above 105C. Basically device failed during our validation and testing process and we released the device with a reduced ambient temperature range to prevent issues from customers designing this device into systems. We didn't see failures with respects to other specifications so only the TA is reduced. 

In conclusion - we saw issues when we did validation above 105C and nothing in the datasheet really would suggest that would happen, but if this device is used don't use it in ambient temperatures above 105C for best results. 

Best,

Parker Dodson

Nakashima-san,

We don't guarantee operation above 105C ambient - so if your systems runs at > 105C ambient you add a lot of risk because we don't guarantee operation past that point and any damage that occurs could be due to non-conformance of limiting values. So regardless if your common mode voltage is lower  - there is still risk added.  Running system above 105C does not guarantee damage since the junction temperature can reach higher - but past 105C we don't guarantee conformance to datasheet parameters. 

The electrical conditions that need to be respected to prevent damage are listed in the abs max section of datasheet

1.Supply voltage specifies voltage w.r.t. GND at the VCC pin - which is -0.5V to 7V

2. Voltage range at bus pins - so the A and B pins ratings which is -70V to 70V w.r.t. GND

3. Voltage input range at logic pins - which are the other inputs on the device - is -0.3V to VCC + 0.3V w.r.t. GND. So the logic input pins are dependent on the voltage at the VCC pin. 

However to keep the device conforming to datasheet specifications - the recommended values should be followed:

All of these specifications need to be respected for the datasheet performance to be guaranteed - and 105C is the max ambient. 

Please let me know if you have any other questions!

Best,

Parker Dodson

Nakashima-san,

There is risk of application failures when you put the ambient temperature above 105C - and we don't guarantee performance. That doesn't mean that the device will break if ambient is above 105C - but performance could be degraded and you could see behavior that isn't conducive to a functioning application. 

Essentially "RECOMMENDED OPERATING CONDITIONS" are the conditions to keep the part bound by datasheet and will help prevent application failures due to comms issues - so above 105C the behavior of the device isn't well defined.

The "ABSOLUTE MAXIMUM" conditions are the conditions that if violated will cause damage and could permanently ruin the device.

So essentially if TA > 105C but TJ < 150C the device may not be damaged - but behavior isn't guaranteed and it may not comply with RS-485 requirements. So to mitigate that risk keeping TA <= 105C is the most advisable pathway forward. 

Best,

Parker Dodson