What am I doing wrong with the l6470 stepper driver?

[kirlik]

We develop electronics for controlling multiple stepper motors and use the L6470 as drivers. Radiators with fan cooling mounted on the chip of the driver (above). The current does not exceed 2 amperes. Radiators remain cold.

The problem is that drivers after working on hold for about 40 minutes seem to overheat and degrade. The overheat warning flags appear immediately before the overheat shutdown.  

After the driver shutdoun it loads the SPI and all drivers on the bus stop responding.

Once an overheated driver starts to shut down after a few minutes or seconds of operation, even without a connected motor.

What could be the problem? Maybe I have to cool the drivers only from the bottom?

Thanks

[Cristiana SCARAMEL]

Hello,

which is the holding current value?

When the device reaches the thermal shutdown threshold, it goes into thermal shutdown condition: the TH_SD bit in the STATUS register is forced low, the power bridges are disabled (bridges in high impedance state) and the HiZ bit in the STATUS register is raised.

The thermal shutdown condition only expires when the temperature goes below the thermal warning threshold (even without a connected motor).

Concerning the L6470 power dissipation the first suggestion is to maximum the ground area below the exposed PAD adding vias to favourite the heat-sink and cooling option.

The heatsink can be directly pasted on the package of the L6470 using a uniform layer of thermal conductive glue or an adhesive foil between the heatsink and the topside of the package.

[kirlik]

Hello!

Thanks for the answer.

But we found out what the problem was.

The topologist incorrectly drew the landing place for the VREG to the ground tantalum capacitor (wrong polarity). As a result, the LDO stabilizer slumps and, apparently, the reference voltage became unpredictable. Because of this, apparently, the Comparators in the overheat protection circuits did not work correctly.