Investigating the issue one option is that what snapped the TSP54060’s is that my PCB tracks are to close for 60V. You need close to 3000V per cm to create an arch and that is 30V per 0.1mm. I can’t see a weak point, but those pins are 0.2mm apart. A bit of extra solder tin on them is all that is needed and 35V is suddenly dangerous. Again I can’t really see anything, but I realized that a MSOP might be to small to actually support 60V safely.

I will try a different circuit, but I will also knock up a few test circuits with different DC/DC designs to see if I can find a stable 60V design. In the meanwhile I will test on 24 and 12 V because I also want to test he actual motor driver. I also realize that as DRV8313 also have 0.2 mm between pins and I actually limited that to 0.15mm as I widened the tracks – I might have a second 60V issue here. Now 60V was never a main objective on this small controller and I am not sure this is the problem, but standards indicate that I need more distance.

I received the MC3X60 Motor controller PCB’s yesterday and as always it is awesome to see how small my designs are. As this is the first time I use TSP54x60 I instantly assembled this to test and was pleased to see 3.4V out.

This circuit worked well giving 3.4V out with input from 12 to 30V, but TPS54060 snaps as I try 35V input.

I received MC3X60V yesterday and was very pleased to see the DC/DC actually working. I had to adapt values to E24/E48 series – R7 became 240K, R6 became 75K, R4 became 33K, but it gave 3.4V out which is fine. I can adjust it back with a E48 combination of R4/R5 later, but the requirement is actually 3-3.6V. As I turned up the Lab PSU Input it works perfect up to 30V input, but snaps as I try 35V. Exact same behavior on two different TSP54060 chips so far. 

This was a bit disappointing because it should not have snapped before I reach 65V, but I will test with TPS54160 and TPS54260 as well. I will also solder up a 2nd circuit. I also detected that the circuit behaved strange if I did not have a 1000uF capacitor over the 60 attached. I have double checked the circuit and components – it is only the TPS54060 that snaps.

My first thought is that I have gone wrong by leaving pin 3 and pin 6 floating. Pin 6 can be left floating it states, while pin6 is an output signal.

Regardless – I also have TSP54160 and TPS54260 chips to test + I only planned to develop with 12V anyway, so I can continue on two paths here (1) testing 60V PSU and (2) testing the rest of the motor Controller.

Don’t worry, I will get to the bottom of it. But, as usual I am my own enemy and don’t make breakout boards I can test new circuits With easily. It is straight on a dense, small design. I am a bit spoiled as I get things working most of the times 🙁

Always funny to share 3D models. This shows the right side of the new 60V Universal Motor Controller. I have spaced out the MOSFET channels and moved all components top-side as well as added 2 temperature sensors, a new 60V DC/DC, capacitors on board and enabled JST channel connectors. I have routed 1 channel, but need to route the 3 remaining (copy) and then comes the big question.

To support more than 15A I need to lay down solder tin on the paths up from the power connector and I also need a wire from the between MOSFET’s to right side of the shunt. I will in reality need 2x3mm holes for that wire and I need to find those 6 mm. If I push those capacitors further to left I will have no room for MCU or I will need to exceed 100mm. One alternative is to push the right power lane to bottom that is ground plane anyway.

I am very happy with MC4X as is, so I am looking forward to this modified board that deal with the remaining issues. It will still be work in progress for a week or so, but I think we might be assembling this during x-mas.

So will this be a 1KW, a 3KW or even a 6KW design? As Is we talk about 60A @ 15A per channel – that is 3600 Watt limited only by power lanes. If I increase to 50A we would be talking 12KW – again the real limiter here is not each channel but those lanes feeding each channel. 12KW would require support for 200A – so no – it is not impossible, but it would require some more space – lol. It is just funny to think that it now should be lanes and wires that limit this design. This amount of energy from a 100x40mm board is insane!

This show the new current sensor with INA194. The main reasons for changing to INA194 is that this supports -16 to +80V sensor range on high side + the chip is SO23-5 package that is a bit easier to mount than INA210 was.

C15 is a filter capacitor mounted as close to the shunt as possible. C25 is another filter mounted as close to V+ as possible and R32/C32 is a classic low pass filter. C25 is absolutely needed attempting to reduce noise on 3.3V as much as possible. The two other filters can be discussed. They can actually be done in SW as well.

I use a 0.001R shunt and INA194 do 50X gain. It is pin compatible with INA193 and INA195 that does 20x and 100X gain. With 1mOhm shunt we will get 15mV at 15A which amplified with 50X will be 0.75V. Also 15A over 0.001 is 0.225W. For a 15A design we can benefit from increasing the shunt to 4mOhm as this will be 0,9W and full 3V at 15A. Using a 0.001Ohm is actually a 50A design. The concern is currents below 1A. 1A is 50mV and max sensitivity for a 12 digit ADC is 0,007mV. In theory we should be fine, but I am worried about the signal/noise at these low currents. I will however need experience on this, so it’s nice to have gain and shunt options to play with. For a low current we should increase Shunt, but I will not worry too much about low currents on this design. I am not going to use a 3KW design to run a small, fiddly motor as I have other controllers for that.

With regards to 15A versus 50A design. The PSU lane is currently 4mm and limiting the total current usage to ca 15A. After this the PCB itself will start to heat up. I can easily fix that by using the trick of extra solder tin on the path. The 2nd limit is the lane from the Half-H-Bridge to the Shunt that will sustain 15A, but need to be a wire for 50A. If I replace this with a wire top-side I can also support heat-dissipation on the MOSFET through the PCB and a heat-sink directly on bottom side with a thermal layer will cool down both PCB and MOSFET’s to assist. I am more and more considering to just do this change, but let us see as I am also running tight on space here. 

Comparing this with the MC3P design I am using 15mm wider for 1 extra channel, main capacitors on the board and temperature sensors on PCB. I would actually struggle to get main capacitors on the MC3P design at all. I want to test DRV8301 anyway for fun, but the only functionality I actually lack is the is the over-current trip in DRV8301. We can do the same in SW, but an analogue trip is faster. Assuming I upgrade this design to 50A it would not make sense to use the more limited MC3P design at all – that said – I actually want to test DRV8301 so don’t worry – I will complete this as well in time.