TIDA-00120: Programming and Heatsink questions

Brian Angiel

Expert 3345 points

Part Number: TIDA-00120

I'm back on this design and have some questions:

I don't see a programming header for the MSP430 on the design. Am I missing it, or do I need to add a header, then use something like http://www.ti.com/tool/EZ430-F2013?
Going back to the heatsink question from my previous thread, if I swap MOSFETs to TO-220s, then can I solder the tab directly to the copper or will I need a heatsink? Is it still the case that I don't need the heatsink if the MOSFET RSDON is such that the heat dissipation doesn't exceed the maximum junction temp of the FETs?

Thanks,

Brian

over 5 years ago

0 Bart Basile over 5 years ago

TI__Intellectual 2760 points

Brian,

J6 has the programming interface. It uses spi-bi-wire, which you can learn more about here: http://www.ti.com/lit/an/slaa754/slaa754.pdf

You would not be able to use the tabs directly to the copper as it would create a short as the tabs are all connected to the mosfet drain. You will have to calculate the losses using the new mosfets, and use that to determine the heating. To get a ballpark on the losses, you can use the Power Stage Designer: http://www.ti.com/tool/POWERSTAGE-DESIGNER

The process for determining the heating is outlined in this article: https://www.electronicdesign.com/boards/calculate-dissipation-mosfets-high-power-supplies

You may not need a heatsink, but I can't say for sure. There are many available on the open market that simply attach to the tab.

0 Brian Angiel over 5 years ago in reply to Bart Basile

TI__Expert 3345 points

Thanks, Bart.

I've got a couple more for you:

It looks like the PCB is powered from solar panels and not the battery AND J4 must be in place for this to work--is this correct?
I'm trying to wrap my head around the P-EN signal in the schematic. It's used to enable Q1. However, if this is ever disabled, then the MCU looses power, right?

Thanks,

Brian

0 Bart Basile over 5 years ago in reply to Brian Angiel

TI__Intellectual 2760 points

Brian,

Yes, J4 must be populated to power the MCU from the onboard regulator.

When there is no panel voltage present, current can flow through the body diode of Q2 and Q4 to provide power to the system. The software is designed to prevent the system from switching if the panel voltage is too low.

There is more info on how the panel can still power the system when the MCU is off here: https://e2e.ti.com/support/tools/sim-hw-system-design/f/234/t/750664

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TIDA-00120: Programming and Heatsink questions