DRV8301: possible to use it without SPI? - Problems with Output signal

Yes, the default settings of the SPI should be ok for operation. I would more inclined to believe there is a soldering issue.

I would double check all of the pin connections.

Can you report the voltage at the AVDD, DVDD, and GVDD pins with EN_GATE = HIGH.

Can you share a schematic with how you have the device connected exactly?

Please triple check that the PowerPAD is connected to electrical GND. The device will not function without this.

Thanks for your answer!

All the pin connections are checked and are good! the schematic is the same like in datasheet.

After i wrote this post yesterday i substitude some of my cap´s because it seems to be that some of them are not supporting 25V-operation!

The second thing i did was to slowly increase the volltage(24V) at startup. And the DRV8301  works partly. The Gate´s of the top-FET´s where driven with the PWM-Signal like i put on the input. The Problem that nothing came out of the DRV8301 is solved, but all three of the buttom-FET´s became no signal or just a little pulse. Does anyone have had this problem?

Today i will check all config´s again and report when it does not work!

By default the DRV8301 is in 6 PWM mode. It requires both the PWM and inverse PWM (INH_X, INL_X) for operation of the half bridges in this mode. You can check the datasheet for the truth table.

Thanks for your answer. I don´t know the mistake but now it works. But I have another problem :-)

I want to switch on the top switch of the first half-bridge(the bottom-switch is off) and switch on the bottom-switch e.g. of the second half-bridge. The Gate signale of the top switch is not 50% PWM as I put at the INH_A pin. The INL_A pin is low. And the Gate Signal is like an very noise signal at 10V. Could it be that the driver won´t work if there is no motor connected?

Thanks,

Heiko

Hi Heiko,

Are you in 6 or 3 PWM mode? In 6 PWM mode you need to supply the inverse signals as well. Can you supply a scope capture of the waveforms?

The driver should have no issues even without a load.

The DRV8301 is in 6 PWM-Mode. I´ll make some pictures tomotrow. 

It also could be that my setup is not really good - I haven´t found an mistake so far. I tilled a new circuit board and than I will soldering it a second time, with better cap´s.

I´m wondering why it works when I apply two complementary signals, it also works when Iapply a PWM Signal on bottom switch and a low signal on the top switch but not in the other way(PWM on top switch, and low on the bottom switch).

Thanks,

Heiko

When you apply 0-0 to the inputs you end up with a High Z state on the outputs. It is hard to predict the state of the voltage in Hi-Z.

It is possible that this is causing the differences in the waveforms you are seeing.

I don´t apply 0-0, if I do this everything works. It´s when I apply following:

T0         T2          T4 

T1         T3          T5

Red means 50% PWM

Yellow means 0V

It´s not only when I apply T0 and T3 but also when any top switch(T0,T2,T4) is on and the complementary bottom switch (T1, T3, T5) is off. But that are the situations I need to commutate my BLDC.

Thanks,

Heiko

You are applying when using 50% duty cycle for one side and low for the other. The PWM is HIGH for 50% and LOW for 50%.

Take a look at the DRV8307 datasheet. Page 13. It gives a standard table for how you commutate a BLDC motor.

In the PWM (drive state) there are two ways to handle when the PWM signal is low. You can either Hi-Z the outputs or drive it actively low. We call these asynchronous and synchronous rectification.

If you Hi-Z the half bridge, the signal will not pull low but instead float.

Ok if I reference the page 13 on DRV8307 datasheet e.g. State 2 doesn´t work with my DRV8301, because if I apply the PWM Signal on the INH_A pin (and 0V on the INL_A pin) the PWM signal that should be applied on the top switch´s gate isn´t like a PWM signal but a noisy high signal (that I haven´t applied). Do you unterstand?

Is it possible that this could be because ther is no load at the FET´s?

Thanks,

Heiko

Try adding a 10k pulldown on the output. This should give you a clean signal.

Yes and no. It is related to the load on the half-bridge, but you should understand that there is a difference when going from DRIVE->Hi-Z and DRIVE->LOW when doing PWM.

So I will add one resistor at the GH_A right? I´ve added three resistors to simulate the motor but without an effect.

The high impedance state which I "apply" when I want to disable one switch is taken as low signal because of the dropdown resistor of the DRV. Or what else do you mean? I know the difference between switch is in high impedance or it is applied a low voltage.

I will reflect your answer again!

Thanks,

Heiko

Were the resistors you added to simulate the motor, SH_X to SH_X orSH_X to GND?

Try adding a resistor from SH_X to GND for each half-bridge.

Good morning,

I´ve added an resitsor (SH_X to GND) and the problem with the not-switching top-switch is solved. It seems to be that the problem occurs if there is no load! The configuration SH_X to SH_X is not working, maybe my load was to weak - I´ll try another resistor.

I´ll also correct my software(I found a little mistake in my strategie to switch the FET´s) and report again if it´s not working.

Thanks a lot,

Heiko