• Resolved

THS6184: reason for high variance on thermal resistance QFN/HTSSOP

Part Number: THS6184

Hello,

can somebody explain why the QFN vs. the HTSOP package has such a high difference:

QFN theta_jc=1,7°C/W,

HTSSOP theta_jc=27.5°C/W

although both devices have an exposed pad does nto explain the delta of more than 10x

Is there an alternative device providing:

4-channel,

>30 Volt

>35mA drivecapabiltiy

bandwidth is probably too high and current feedback provide high offset, lower woudl be better.  Estimated PD *1.2 Watt

Thanks, Bertram

  • Hi Bertram,

    I somewhat agree with your assessment that the theta_jc for QFN and HTSSOP should not have such a huge difference, although it could be a typo for QFN theta_jc that actually needs to be 17 'C/W. Let me check with the thermal packaging team on this and get back.

    I don't think we have an alternative device with 4 -channels that supports >30V supply and 35mA drive capability in voltage feedback configuration that could provide lower offset. The closest we have is the LMP8674 in voltage feedback configuration but its max PD is limited to 0.86 Watts.

    Best Regards,
    Rohit
  • In reply to Rohit Bhat:

    Received the following updated thermal characheristics to be added to the Datasheet

    The PWP (HTSSOP) thermal model is finished, and the θjc to the top of the case = 23.9 °C/W as shown below, which is a little lower than the 27.5 °C/W in the PDS.  The θjc to the power pad (bottom of the case) = 1.7 °C/W as shown below.

    Apparently, the PDS has the HTSSOP θjc to the top of the case and the QFN θjc to the bottom of the case.  I think the HTSSOP should be changed to the bottom of the case.  The θJA is more relevant to the customer, and those numbers are close for the two packages as shown below.

    Device Name THS6184RHFT  

    No of Pins 24  

    Package Designator RHF  

    Leadframe (or substrate) Number - 7 digit 6448517  

    Is it Stacked Die or MCM ? No  

    Die Size(s) and Description(s) 2528.062 x 3221.99

    Result- Theta JA-High K (standard datasheet value) 33.4  

    Result-Theta JC, top (standard datasheet value) 23.1  

    Result-Theta JB (standard datasheet value) 11.7  

    Result- Psi JT (standard datasheet value) 0.3  

    Result- Psi JB (standard datasheet value) 11.6  

    Result-Theta JC, bottom (standard datasheet value) 1.0