Thermal Characteristics for SMPTE HOTLink - CY7B9235/CY7B9335

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.