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RC4558: Thermal Resistance

Part Number: RC4558


Could you offer the RθJC and Tc(Max)?

In the d/s, there are only TA、TJ、RθJA, they are not enough for thermal calculation.


Brian W

  • Brian,

    Which package or two packages do they need data?

    If they are using RθJC parameter then they are using a contact heat sink or they are planning to use the RθJC parameter incorrectly.

  • Hi Ron,

    Thanks. The package type is RC4558IPWR. There is no heaksink on the top of device attached in application. What temperature point RD can be easily obtained are T_case and T_ambient.

    Pls offer the Theta_jc in advance. We will also communicate the correct measurements of the junction temp with SMD package. However in the d/s, I don’t even find the thermal metrics that is independent with pcb size!

  • Brian,

    Theta JC, top 67.1 C/W
    Theta JB 112.5 C/W
    Psi JT 8.4 C/W
    Psi JB 110.7 C/W

    If they know the top of case temperature (T) then they can estimate the die temperature (D) as D = T + [Psi JT] * [power dissipation].  

    The Theta JC value is nearly useless because the majority of the heat does not escape through the device top; actually very little does. That is why the top of case temperature is nearly as hot as the die.