Thermal Characteristics for SMPTE HOTLink - CY7B9235/CY7B9335

Version 1
    Answer: Title:

    Thermal Characteristics for SMPTE HOTLink - CY7B9235/CY7B9335



    Questions:

    - How do I calculate case temperature?

    - How do I calculate board temperature?

    - What is the maximum ambient temperature for HOTlink?

    - What are the Theta-JA and Theta-JC values?

    - What is the maximum junction temperature, Tj?



    Response:

    Because the thermal characteristics are dependent on the ambient temperature and power used by the system, both the equations and values are provided below.



    Tj = Junction temperature

    Tb = Board temperature

    Ta = Ambient temperature

    Tc = Case temperature



    Theta-Ja = Junction to ambient thermal resistance

    Theta-Jb = Junction to board thermal resistance

    Theta-Jc = Junction to case thermal resistance



    Pd = Power used by the device.



    TEMPERATURE RANGES:

    Commercial: Ta = 0 to 70 °C

    Industrial: Ta= -40 to 85 °C



    KNOWN VALUES

    These are gotten from the table below.



    JUNCTION TEMPERATURE

    Tj = Theta-Ja*Power   Ta (1)



    BOARD TEMPERATURE

    Tj = Theta-Jb*Power   Tb (2)

    so Tb = Tj - Theta-Jb*Power (3)

    >From Eq(1) and (3) we get

    Tb = (Theta-Ja - Theta-Jb)*Power   Ta (4)



    CASE TEMPERATURE

    Tc = Tj - Theta-Jc*Pd (5)

    so Tc = (Theta-JA - Theta-JC)*Power   Ta (6)





                                                                                                                                                                                                                                                                                                                                                                                                                    
    CY7B9235/CY7B9335 Thermal Values
     CY7B9235CY7B9335
    Part Number - Theta-JA (°C/W)Theta-JC (°C/W)Tj (°C)Theta-JA (°C/W)Theta-JC (°C/)WTj (°C)
    270JC271591.6245104.8
    400JC271591.6245104.8




    Useful Link:

    CY7C9235 SMPTE-259M/DVB-ASI Scrambler/Controller (http://www.cypress.com/?rID=14213)



    CY7C9335 SMPTE-259M/DVB-ASI Descrambler/Framer-Controller (http://www.cypress.com/?rID=14214)



    Keywords:

    HOTLink, SMPTE, CY7B9235, CY7B9335, thermal characteristics, Theta-JA, Theta-JB, Theta-JC, junction, temperature, Tj, case, board, Ta, Tb, Tc.