DRV2510-Q1: An question about the boot strap port of DRV2510

Hi, Yun,

Do you have details about the resistor connection to the bootstrap pin and the resistor value range that you would use?

Do you have the complete schematic including the resistor?

Best regards,
Luis Fernando Rodríguez S.

Hi Luis,

Thank you for your reply as soon as possible.

 We would like to insert a resistor between BSTP condenser and OUT pin as below (orange rectangle).

However, we don't certain how to choose a proper resistor, whether hundreds of ohms can be enough?

 We want to add the boot strap resistor is because the serious noise at 1.2MHz when we tested DRV2510 or 2511 with spectrum analyzer.

To solve this issue, could you please let me confirm two questions as below.

  1st, from a previous question as below, the DRV2510 is made up of soft switching architecture as link below.

However, we checked the digital PWM waveform in output side with oscilloscope, that seems not really soft switching mode as expected.

So we want to understand, is there any condition so that the soft switching mode can be achieved, e.g. add a boot strap resistor.   

https://e2e.ti.com/support/motor-drivers/f/38/t/942325

 2nd, if you have any other suggestions to cancel the noise issue @1.2MHz, please instruct us.

Best regards,

Yun Lin.

Hi, Yun,

We actually don't recommend to add a resistor in the BST_P to OUT connection. Please remember that the output will handle a high current rate, having a resistor of hundreds of ohms value may cause a high voltage drop at the output. In case you see an improvement on the design with an output resistor, I would recommend to use one below 10ohms. However, we cannot guarantee that it will work properly since this is not a common usage.

Regarding the noise cancellation, are you looking to cancel the noise on the solenoid stage? Or on the rest of the circuitry? I mean, where is the noise located and where would you like to remove it?

Best regards,
Luis Fernando Rodríguez S.

Hi Luis,

Sorry for forgetting the condition of DRV2510(or 2511) when we do the noise test.

1. frequency setting is 400KHz;
2. DRV2510 is active;
3. there is not any input signals, which means there is only duty50% and 400KHz PWM signal from output pin.

We have done the radiation and conduction noise test, where a tough spike @ 1.2MHz had been observed in both methods.

And the check point of conduction method is the VDD line.

Therefore, I think the noise spreads the whole of the circuitry.

Best regards.

Yun Lin 

Hi, Yun,

Have you already tested the output LC filter in order to reduce these spikes?

This document and tool can be used in order to adjust the cutoff frequencies.

https://www.ti.com/tool/LCFILTER-CALC-TOOL

https://www.ti.com/lit/an/slaa701a/slaa701a.pdf

Best regards,
Luis Fernando Rodríguez S.

Hi Luis,

 Thanks for your information on the LC filter. We will try the LC filter to validate the efficacy.

 By the way, from the oscilloscope wave form result, there is not really the soft-switching when there is neither snubber nor LC filter in the output line.

Do you mean, if we want to activate the soft switching mode, the LC filter is necessary.

Best regards,

Yun Lin    

Hi, Yun,

The DRV2510-Q1 doesn't have soft switching mode. However, the harmonics generated by the switching frequency can be reduced with the help of output filters. Since these frequencies are in a non-operable band, the solenoid or the connected load shouldn't be affected by this switching noise.

Best regards,
Luis Fernando Rodríguez S.

Hi Luis,

 So, DRV2510 and DRV2511 can not be used under softswitching, right?

 Please let us confirm the information from another answer as below link too.

https://e2e.ti.com/support/motor-drivers/f/38/t/942325 

Best regards.

Hi, Yun,

Could you clarify what you mean with soft switching? I think we could have a misunderstanding of this feature.

Best regards,
Luis Fernando Rodríguez S.

Hi, Yun,

Excuse me, do you have a feedback on this?

Thank you.

Best regards,
Luis Fernando Rodríguez S.