Strictly necessary cookies are on by default and cannot be turned off. Functional, Performance and Tracking/targeting/sharing cookies can be turned on below based on your preferences (this banner will remain available for you to accept cookies). You may change your cookie settings by deleting cookies from your browser. Then this banner will appear again. You can learn more details about cookies HERE.
Strictly necessary (always on)
Functional, Performance and Tracking/targeting/sharing (default off)
Note: For spec numbers 001-00001 to 001-99999, the KBA number is five digits; for spec numbers 002-xxxxx, add '2' to make it a 6-digit number. For example, for spec 002-12345, the KBA number is 002-212345 to distinguish it from KBA12345 for spec 001-12345.
Question: How can we calculate the maximum operating junction temperature for clock devices?
Answer: Maximum Operating Junction temperature (this is the maximum junction temperature at which the thermal characteristics of the IC are guaranteed).
We can use the below formula to calculate the maximum operating junction temperature:
Tjmax = Theta Ja * Pd(max) + Ta (max)
Tj is the Junction Temperature
Theta Ja is the Junction to ambient thermal resistance
Ta = Ambient temperature = 85°C
Pd= Power dissipation = VDD * Itot
Total current, Itot = Idc + Iac
Idc value can be found in the datasheet
Iac = K*C*V*F
K = 1/2 for 50% duty cycle. You can modify this parameter accordingly.
C = Load Capacitance
V = VDD
F = Frequency
Then calculate total power by multiplying by VDD.
Please note this is the max operating junction temperature that the device will reach as per the application or as per the values you enter or select.
Some datasheet doesn’t show the current, IDC and IAC separately, it shows the Total current “Itot” at a specific frequency. For this case we recommend the linear interpolation by C, F and V because that will be the worst case.
For example in the CY27410 datasheet, IDDO for CMOS, specified 6.0mA(max) at 10-pF 33MHz, so if you use 66MHz, the IDDO will be 6*2=12mA for 66MHz operation, and so-on.