STSPIN840: Why does the En/Fault doesnt go to low if SNSA is higher than VrefA?

[PJust.1]

Hi All,

I tested the motor driver STSPIN840. I'm able to limit the current through the motor. But i dont see the Fault Pin going down to zero if the driver limits the current. If i do a short circuit on the output the Fault Pin goes down to Zero.

What can i expact for signals on the fault pin if the SNSA is higher than Vref but lower than the overcurrent value of 3A?

BR Philipe

[Cristiana SCARAMEL · Accepted solution]

Hello @PJust.1​ and welcome to the ST Community.

The EN\FAULT pin is forced low through the integrated open-drain MOSFET when a failure occurs.

The "failure" can be an overcurrent on the related power bridge (3 A typical value) or an overtemperature (160 °C typical value).

The SNS and REF pins are involved in the PWM current control (see to STSPIN840 datasheet starting from page 15).

The PWM current control does not trigger the FAULT pin signal.

So your STSPIN840 is working properly.

Let me know if I solved your doubts, if so please "Select as Best" label.

[Cristiana SCARAMEL]

Hello @PJust.1​, any comments from you?

[PJust.1]

Hi Christiana, thanks for your answer. But this means if i protect the motor by using a Vref smaller than Imax. It will not create a fault. The idea was to change the direction of the motor if the Vref is higher than Vsens.

So this means I have to measure Vsens to detect over current.

BR

[Cristiana SCARAMEL]

Hi @PJust.1​,

as already mentioned the REF pin is used to control the current.

When the VSNSX > VREFX the current limiter is triggered and the

low sides of the full bridge are turned on (slow decay) for a off time (sert .

The idea was to change the direction of the motor if the Vref is higher than Vsense.

You can implement this function externally monitoring the sense voltage, when Vsense is higher than your reference you can change the PH signal of your bridge and change motor direction.

[PJust.1]

Okay thanks for your answer. Then i will use a ADC to detect over current.

BR