• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 29 subscribers
  • Views 1149 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.

PowerPAD (DRV8825) to 34.5oz copper + fin heatsink

Matt Heyse
Prodigy 10 points
Other Parts Discussed in Thread: DRV8825, DRV8711EVM, DRV8711, BOOST-DRV8711, DRV8829, DRV8829EVM

I'm looking at massively increasing the direct PowerPAD cooling of the DVR8825, well above and beyond what it would see on a normal PCB

This is because TI doesn't have a version of the DVR8825's gate logic exposed to drive external H-Bridges, were limited to just 4w internally (2.5A @ 85C°).

Copper Shims are cheap. (20mmx20mm 1.2mm/34.5oz thick  $.35)  as compared to the DVR8825's cost. 

For Hot environments, to better manage heat I want to solder the DVR8825 to a copper shim (basically a 34.5oz one layer PCB that has no fiberglass),  The pure copper acts as a Heat Spreader, which then is thermal pasted to a CPU (135w) heat sink.

But the PowerPAD Support documentation doesn't really cover the heating requirements for anything above 2oz. Are there any Solder/Oven considerations as the copper plain gets thicker?

The DRV8825 is easily programmed to exceed its max current rating of 2.5A.  With forced cooling is it possible to get 3.5 Amps? (4.5HP/175cfm shopvac, pulling air through 135W heat sink) This would increase the internal heat production from 4W to 7.7W (85C° internally), but the direct mounted cooler should easily handle that, and would likely keep the PowerPAD, below ambient. 

The problem is that I don't know how the H-Bridges were built in the DVR8825.  So I don't know if there are other current limitations of the design (other than Thermal) like conductors so small they act as fusible links a 2.7A   OR because of Thermal De-rating to get  a 125C° device, the H-bridges can actually safely pass 10A if the Silicon die stays at 25C°. I just don't know, So I'm asking.

  • 0
    TI__Guru** 114905 points
    Hi Matt,

    If you are looking to get 3.5A, the DRV8825 is not the part. The device overcurrent can trigger at 3A.

    There are a couple of options. First is the DRV8711 with external FETs. There is a DRV8711EVM and a BOOST-DRV8711 Launchpad for evaluation.

    Another option is two DRV8829. In conjuction with a mcu to set the reference voltages, the two devices can achieve 5A and high levels of microstepping. A DRV8829EVM is available for evaluation of this option.