DRV8838: DRV8838: High impedance mode (sleep) current leakage

Hi Juan,

Try setting all the inputs low to best minimize power loss and leakage current. When the VCC and inputs are high this will cause the driver to draw more power and lead to more leakage current.

Best,

David

Hello David,

I can confirm all input pins are set to low when the test is made. I can show my setup but it is pretty simple and the behavior easy to reproduce, just set all inputs to low, VM to 9V, VCC to 3.3V, and place a current meter in the circuit. In that setup with both outputs floating you will see no leakage current flowing, but if you tie any of the outputs to VM you will see a few mA of current. If you tie both outputs you will see double that current. 

Is this normal behavior? That is something concerning as this means this Ic can not be used in low power devices where the outputs are externally pulled up for needs in the application.

Thanks,

Regards.

Hi Juan,

Yes, this is a normal behavior for the total leakage current. 

I have recreated the test in the lab and confirmed with the settings listed above we are also seeing leakage current in the mA range. 

Best,

David

Hi David,

Thanks for confirmit it. Those are some very bad news. Meaning this IC can not be used for low power applications in those cases.

I took a look at alternatives (with few modifications) and i found some:
 - DRV8210
 - DRV8212
 - DRV8220

So, my next question is: Have those devices the same behavior? or I will be able to use those instead?

Thanks,

Regards.

Hi Juan,

The DRV8210 or DRV8212 would most likely be a suitable option for the application because of the ultra low power sleep mode specification. 

After testing the DRV8210EVM in the lab, the leakage current is just under the 2mA  between OUTx and GND, and around 3mA between VM and OUTx.

Best,

David

Hi David,

We bought some DRV8210, DRV8212 and DRV8220. for the moment we only tested DRV8210, DRV8212 and it is not a solution because (same as in your tests) it still consumes a few mA of leakage when in sleep mode and outputs are connected to high.

This is not a valid as this will keeps draining the battery when it should be a low power solution.

Looking at the DRV8210, DRV8212 datasheets, the current should be less:

On the other hand the DRV8838 should be even less:

Tomorrow I will tests DRV8220 and share the results. But unless i'm not seeing the datasheet correctly or i'm missing something the datasheet information is not correct and should be fixed for those devices.

Thanks,

Regards.

Hi Juan,

Please let me know your findings.

Tomorrow I will also speak with systems about reducing leakage current or finding a device with lower sleep mode leakage. 

Best,

David

Hello David,

After testing the DRV8220 finally we have the expected behavior. With the same setup as before with device in sleep mode and outputs tied to high we have 400 uA. If we look at the datasheet the values coincide:

Sleep mode + two outputs tied to high = 960nA + (186uA * 2) = 373 uA. Similar to our results.

Unfortunately we need the total system power consumption (not only the motor driver) to be less than 100 uA, so this motor driver (even if it is working within the expected values) is not suitable for us.

With the DRV8838 we got a valid result, only if VM is below 7V, as it complies with the values of the datasheet (total consumption <1uA). It is a pity that above 7V does not meet the expected.

Thanks for your help, but we will keep looking for alternatives.

Regards.

Hi Juan,

I am glad to have helped. 

May I ask what the application is that the outputs would need to be tied to VM?

If possible, could you send me a schematic to further explain the leakage current?

Best,

David

Hi David,

The application doesn't need to be tied to VM, it is just a way to reproduce the issue. In the real application our motor driver is on parallel with another motor driver whose outputs in idle mode are tied to the high side with a non very high impedance. So when both devices are in idle (our device in sleep) undesired current flows from the other motor driver output to our motor driver output.

Regards.