DRV8824-Q1: the way to detect open load

Takao Yamamoto

Genius 4135 points

Other Parts Discussed in Thread: DRV8824-Q1

Dear all,

Is it possible to detect open load by DRV8824-Q1?

I have understood this device does not have FAULT to detect open load.

However my customer want to use this device and detect open load.

So, I would like to know the way to detect open load.

By the way, does this device show some singular behavior under open load?

If this show something singular, I think my customer can detect open load.

Best regards,

over 10 years ago

0 Rick Duncan over 10 years ago

TI__Guru** 114905 points

Hi Yamamoto-san,

The DRV8824-Q1 does not have open load detection. It may be possible with external circuitry.

Does the customer want open load detection at all times the motor is running, or are they willing to check when the DRV8824-Q1 outputs are disabled?

0 Takao Yamamoto over 10 years ago in reply to Rick Duncan

Genius 4135 points

Dear Rick,

Thank you for you reply.

My customer said that either is fine.

I think that my customer wants more easily system.

Best regards,

0 Rick Duncan over 10 years ago in reply to Takao Yamamoto

TI__Guru** 114905 points

Hi Yamamoto-san,

One possible method of detecting open load is shown in the attached file. This can be done any time the motor is disabled.

The basic idea is to provide a voltage on one side of the coil, then read it on the other side. The voltage will have to be reduced at the receiving side to make sure the micro can accept it.

External Open load.pdf

Each coil has a high value resistor to VM on one side of the coil and to ground on the other side of the coil.

If either coil is open, the gate of the transistor will be pulled to ground. The result will be a logic high at the micro. This circuit was used to minimize GPIOs required from the micro.

0 Takao Yamamoto over 10 years ago in reply to Rick Duncan

Genius 4135 points

Dear Rick,

Thank you for your suggestion!

I would like to check one thing about your attached file.

I could not understand additional circuit.

I added your file about my question.

Question about External Open load.pdf

Please look the attached file and reply about this.

Best regards,

0 Rick Duncan over 10 years ago in reply to Takao Yamamoto

TI__Guru** 114905 points

Hi Yamamoto-san,

Thank you for pointing this out. The line in question should not be there. This was a copy/paste error.

The update circuit without the line in question is attached.

5618.External Open load.pdf

0 Takao Yamamoto over 10 years ago in reply to Rick Duncan

Genius 4135 points

Dear Rick,

Thank you for your answer.
I will share this circuit with my customer.

Best regards,

0 Rick Duncan over 10 years ago in reply to Takao Yamamoto

TI__Guru** 114905 points

Hi Yamamoto-san,

One additional comment about the circuit. The circuit shown requires a FET with a high VGS. This can be lowered by placing a voltage divider on the ground side resistor. Placing two 500k resistors in series would lower the VGS requirement by two.

Also, there is a clamp circuit in the outputs that will limit the voltage to approximately 12V when the outputs are disabled and the resistor is connected to VM. This should be considered when creating the circuit.

0 Takao Yamamoto over 10 years ago in reply to Rick Duncan

Genius 4135 points

Dear Rick,

Thank you for your support.
I will share this with my customer.

Best regards,

Motor drivers

Motor drivers forum

DRV8824-Q1: the way to detect open load