SN75DPHY440SS: what is Ta(Ambient Temperature) and Tc(Case Temperature)?

Hi,

For SN75DPHY440SS, the ambient temperature (Ta) is 0 to 70C.

The case temperature Tc is design dependent.

Thanks

David

David

I have the following questions:

1. Is the Operating free-air temperature the same as the ambient temperature (Ta)?

2. The maximum power consumption of SN75DPHY440SS is 150 mW. Based on my calculation, Ta = 98°C.
   Given that the datasheet specifies 70°C, should Ta be 70°C or 98°C?
   Did I make a mistake in my calculation?

Hi,

1. Is the Operating free-air temperature the same as the ambient temperature (Ta)?

Ambient temperature is the temperature of the air immediately surrounding an object, representing the environmental temperature. Texas Instrument devices marked Commercial Temperature Range function at ambient temperatures between 0°C and 70°C (SN75DPHY440) or between -40°C to 85°C (SN65DPHY440) when proper care is taken to ensure the absolute maximum operating temperatures are not exceeded. 

1. The maximum power consumption of SN75DPHY440SS is 150 mW. Based on my calculation, Ta = 98°C.
   Given that the datasheet specifies 70°C, should Ta be 70°C or 98°C?
   Did I make a mistake in my calculation?

The max ambient temperature for commercial temperature range is 70°C. It is important to understand, in any case, that the critical factor affecting device reliability and functionality is the junction temperature, not the ambient temperature since majority of heat will be dissipated through the PCB board, not the top of the device.

Thanks

David