DRV8307: closed-loop speed regulation

Hi Matt,

After checking, DRV8308 has closed-loop speed regulation but no stall function. Is it possible to recommend the DRV8307 brushless DC driver and MCU for speed loop? Can the recommended chip be used for current loop speed loop?

18-36V. With locked-rotor function, With current protection function, With Hall signal closed loop speed control function. Is there a suitable recommendation for this integrated chip?

Thanks.

Annie

Hi Annie,

We do not have any device which has speed loop outside of DRV8308.

To implement a speed loop, you need to follow the below diagram:

I would start with an MCU with two timers (i.e. MSP430FR2422). One timer will generate the PWM to be sent to the DRV8307, the other timer will be a capture/compare for the FGOUT sped feedback and target speed.

Thanks,

Matt

Hi Matt,

Customer would like to confirm that:

1. DRV8308 is TI’s only device with a speed loop?

2. Can msp430 be used to match DRV8307 for speed loop control? Is it feasible to incorporate the current loop into the msp430, or need TMS28062? 

Thanks,

Annie

Hello Annie,

DRV8308 is the only BLDC motor driver with speed loop integrated.

MSP430 is OK to implement a speed loop, since the BLDC motor commutation is integrated into the driver and the complexity of the loop is small. Only 4 pins will be needed: FGOUT speed feedback, PWM, Target Speed Input, and DIR. The speed loop bandwidth does not need to be very high, since the motor will have a bandwidth in the range of kHz. You can implement a speed loop in TMS, but that MCU is more expensive.

Thanks,

Matt

Hi Matt,

Thanks for your support. The customer still has the following questions that need your help.

Is there a recommended combination solution? Voltage 18-38V (how much is the voltage margin generally reserved)? With Hall, the speed accuracy must be high! Chip with enable control.

MCU+ integrated chip solution? Is there a suitable recommended combination? Complete the closed-loop speed regulation function, as well as stall protection, over-current protection, over-voltage protection, braking, etc. Rated current is about 3a.

Thanks,

Annie

Hi Matt,

Thanks for your support.

The customer's power supply voltage is 18-38V, (long-term power supply is 28V）he wants to

• choose a device with a maximum voltage above 50V; 
• with Hall signal, or without Hall signal but closed-loop speed regulation with MCU;
• High speed accuracy (speed accuracy is controlled by MCU software);
• It is best to bring an enabling control foot to facilitate his logic control

At present, it seems that the appropriate solution is mcu+ integrated chip. He chooses msp430 for mcu, but the integrated chip needs to recommend one or more. The requirements are as follows:

• The maximum voltage is above 50.
• With overcurrent protection function,
• Closed-loop speed regulation is completed by MCU through Hall signal
• Locked-rotor protection, of course, locked-rotor protection can also be realized by software
• Overvoltage protection, brake integrated in the chip

Customer hopes to recommend more suitable chips. The rated current is 3a, if he chooses the internal integrated mos tube, he needs a large current. He is using a brushless DC motor with Hall signal.

Thanks,

Annie

Hi Matt,

Thanks for your strong support. And customer has further questions need your help.

Can TI's open-loop DC brushless integrated chip add a closed-loop speed adapter to achieve closed-loop speed regulation? For example, DRV8307+ closed-loop speed adapter (through three hall signals of the motor) to achieve closed-loop speed regulation.

Thanks,

Annie

Hi Annie,

What do you mean by a "closed-loop speed adapter"? Do you mean an MCU configured for a speed loop?

Thanks,

Matt

Hi Matt,

No, it is similar to the closed loop speed regulation of mc33039. Or tachometer chip, through the three position signal hall signal behind the motor to achieve closed-loop speed regulation. Could TI's open-loop DC brushless integrated chip be equipped with this?

Thanks,

Annie

Hello Annie,

MC33039 or similar device look like they will work, although I would recommend testing it out. The output of the adapter must be a duty cycle.

Thanks,

Matt

Hi Matt,

Thanks for your supporting.

He would like to know how should the adapter output match the drv8307 pin? Is there a recommended matching method?

Thanks,

Annie

Hello Annie,

The control signal (output signal from the adapter to the DRV8307) must be a PWM signal with variable duty cycle.

I think mc33039 as an example has variable duty cycle output and will work.

Thanks,

Matt

Hi Annie,

Is there any additional help needed on this thread?

Thanks,

Matt

You are able to close this thread now. Once there is feedback, I will let you know.

Thanks Annie!