Partial Jag failure?

[techhelpbb]

Originally Posted by kamocat

I did not smell any burning, but it would not surprise me if this was the issue. I will check later.

What I find particularly strange is that it SAYS it's output is zero. I thought this was a calculated value, not a measured value.

There's a voltage VM+ on the Jaguar schematic in the User Manual.

http://www.luminarymicro.com/jaguar

It's connected to a voltage divider to scale it down so it can be input into the microcontroller analog to digital converter.

The Jaguar also has an INA193 on the schematic. That is a current shunt monitor measuring across a 0.001 Ohm resistor on the high side of the H-Bridge. The INA193 is a unidirectional current shunt monitor, but it will survive the reversal of it's input voltage. They made a provision but didn't populate for a bidirectional current shunt monitor.

http://focus.ti.com/lit/an/slyt311/slyt311.pdf

In short, it can measure both voltage and current to the motor....but in this configuration it can't measure any currents going backwards either due to the body diodes of the MOSFETs or the collapse of the motor's field. This circuit is not 'regenerative' so it's not applicable (it might be...in say an electric vehicle application where the motors turn into generators to slow the vehicle down and use the generated power to charge the batteries).

Just keep in mind, however, that when I say it can measure that voltage...it sort of cheats at that. It assumes the MOSFETs are operational and approximately matched.