Approved ambient temperature range and thermal power budget

The thermal power budget must be checked before final installation. There are two relevant heat sources in the CU1521-0020: the basic device and the SFP modules used. Depending on the SFP used, additional internal heat is generated. As a result, the maximum approved operating temperatures of the SFP and/or the basic device may be exceeded.

An SFP generates an approximate internal temperature increase of +7 K/W.

The basic appliance from HW02 has larger cooling openings.

Standard industrial SFPs report a warning from 85 °C intrinsic temperature and an error from 95 °C.

If commercial SFPs with a warning temperature of 70 °C are used, the SFP lines must be lowered by 15 °C accordingly.

Example: In the CU1521-0020 HW01, two SFPs with 1 W each (3.3 V × 300 mA) can be used at Tambient = 55 °C, so that the warning threshold for industrial SFPs is just reached.

Approved ambient temperature range and thermal power budget 1:Fig.44: Approved ambient temperature range as a function of SFP power loss and hardware status (original illustration).
Approved ambient temperature range and thermal power budget 2:

Practical recommendation

Check the power loss from the SFP data sheet in advance. If the ambient temperature is high or two SFPs are plugged in, use SFPs with low power consumption and an industrial temperature range if possible.