• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 31 subscribers
  • Views 957 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM26LV, LM57 : Die Attach Pad voltage rating

Jiri Kolouch34
Prodigy 200 points
Other Parts Discussed in Thread: LM57, LM26LV, LM35

Dear,

in the datasheets for LM26LV, LM57 there is stated that "best thermal conductivity between the device and the PCB is achieved by soldering the DAP of the package to the thermal pad on the PCB. The thermal pad can be a floating node".

What is the voltage limit on that DAP-pad? Is the die insulated by oxide or by junction? I intend to connect it to drain of PMOS, operated from 35V, no fast switching expected (no issues with noise immunity).

Thanks in advance for support!

  • 0
    TI__Expert 7220 points
    Hi Jiri,

    Let me get back to you on this.

    -Michael Wong
  • 0
    TI__Expert 7220 points
    Hi Jiri,

    The DAP is connected to the substrate of the IC. It is not recommended to put any voltage on the DAP besides ground or floating and we cannot guarantee the performance. What is your application for connection to a PMOS?

    -Michael Wong
  • 0 in reply to Michael Wong
    Prodigy 200 points

    Hi Michael,

    intended application: To protect SMT power PMOS against overheating. I have some non-standard voltage limiter circuit that shields 24V circuit from rare spikes up to 45V (not automotive).

    Anyway, in case the P-substrate is tied to thermal pad, there is no way to use it as I intended. If you would know any product with N-substrate exposed (i.e. such sensor EP could float) , I would appreciate your message.

    Regards,

    Jiri

  • 0 in reply to Jiri Kolouch34
    TI__Expert 7220 points
    Hi Jiri,

    The drain of the PMOS does not have to directly touch the DAP for best thermal conduction. I recommend placing the LM26LV/LM57 as close to the drain connection as possible. Now these parts conduct temperature best by either through the ground pin or the DAP so I would orientate the ground pin close to the drain trace.

    Another option is, if there is a heatsink on the PMOS, placing a through-hole package on the heatsink itself. TO-92 packages (LMT84-7, LM35) can be glued on with thermal epoxy and TO-220 packages (LM35) can be directly screwed onto the heatsink. These are analog output sensors so a comparator will be needed for switching.

    -Michael Wong