DRV8350: GHX not working properly for Synchronous 1x PWM Mode

Daniel Mena

Part Number: DRV8350

Tool/software:

Hi!

I hope you all are doing great!
I am working with a DRV8350HRTVT but facing some problems with proper motor rotation. I am using the following conditions:

1x PWM Mode (MODE Pin, 560k Ohm Resistor, Hi-Z)
INHC (Dir, LOW)
INLC (Brake, HIGH)
Hall Sensor signals are directly connected to INLA, INHB, and INLB without an MCU (proper pull-up resistor and filtering are implemented)
PWM signal generated by MCU (STM32, 20 kHz, 10% duty cycle only for testing)
VM/VDRAIN -> Power Supply 16.8V ~ 18V (3A)
IDRIVE -> tied to 3.3V
VDS -> Hi-Z

Since the motor was only vibrating I tried to check what was going on with the signals first (hall sensor, phases, GHX, GLX, SHX). I noticed too much noise in some phases and some gates, so before trying to make it work I decided to remove the motor and only check the expected behavior of the driver.

The datasheet provides the following reference:

DRV8350H (Datasheet)
STATE	INHC = 0			PHASE A		PHASE B		PHASE C		DESCRIPTION
STATE	INLA	INHB	INLB	GHA	GLA	GHB	GLB	GHC	GLC	DESCRIPTION
Stop	0	0	0	L	L	L	L	L	L	Stop
Align	1	1	1	PWM	!PWM	L	H	L	H	Align
1	1	1	0	L	L	PWM	!PWM	L	H	B → C
2	1	0	0	PWM	!PWM	L	L	L	H	A → C
3	1	0	1	PWM	!PWM	L	H	L	L	A → B
4	0	0	1	L	L	L	H	PWM	!PWM	C → B
5	0	1	1	L	H	L	L	PWM	!PWM	C → A
6	0	1	0	L	H	PWM	!PWM	L	L	B → A

Since I removed the motor I could control the hall sensor signals and check the expected behavior. I obtained the following results:

DRV8350H (Measurement, No Motor)
STATE	INHC = 0			PHASE A		PHASE B		PHASE C		DESCRIPTION
STATE	INLA	INHB	INLB	GHA	GLA	GHB	GLB	GHC	GLC	DESCRIPTION
BRAKE	X	X	X	L	H	L	H	L	H	BRAKE
Stop	0	0	0	H	L	H	L	H	L	Stop
Align	1	1	1	PWM	!PWM	L	H	L	H	Align
1	1	1	0	H	L	PWM	!PWM	L	H	B → C
2	1	0	0	PWM	!PWM	H	L	L	H	A → C
3	1	0	1	PWM	!PWM	L	H	H	L	A → B
4	0	0	1	H	L	L	H	PWM	!PWM	C → B
5	0	1	1	L	H	H	L	PWM	!PWM	C → A
6	0	1	0	L	H	PWM	!PWM	H	L	B → A

It seems like the gate for the high-side is not working properly (not for all cases though).

I checked the circuit and driver configuration many times, but I can't pinpoint where the problem might be.

I attached part of the schematic as a reference.

Could you please guide me on what else I can try to solve this problem?

Thanks in advance!

7 months ago

0 Yara Al Shami 7 months ago

TI__Genius 14935 points

Hi Daniel,

Not sure what is happening here but a little more information from your end might help me out.

You mentioned there's a lot of noise on your outputs? What is your IDRIVE set to? and what MOSFET are you using?

Do you happen to have the following waveforms:

GHx to SHx

SHx to GND

GLx to GND

Regards,

Yara

0 Daniel Mena 6 months ago in reply to Yara Al Shami

Prodigy 20 points

Hi Yara!

Thank you for your reply. It took me a while to take some measurements but I hope they help root out the problem's cause.

1) Yes, there's some noise (oscillation, spikes/peaks) especially when I connect the motor.

2) IDRIVE is set to 3.3V. A previous project at the company used it in that way, however checking the datasheet more thoroughly I see that it could be tied to DVDD. My next test is to try to route it to DVDD and see if that is causing the wrong behavior.

3) I am using "TPW1R306PL,L1Q" for the MOSFETs.

As for the waveforms I tried with 3 different states (0-0-0 Stop, 1-1-0 B->C, 1-0-0 A->C).

As summary, I put the information in a table.

If you need some more information or the raw data please let me know, I'll try to prepare it ASAP.

Thanks for the help!

0 Yara Al Shami 6 months ago in reply to Daniel Mena

TI__Genius 14935 points

Hi Daniel,

I think the issue is simply the IDRIVE setting is far too high for the MOSFET that is being used.

Please read the following two FAQs:

https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/796378/faq-selecting-the-best-idrive-setting-and-why-this-is-essential

https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1236302/faq-drv8353rs-evm-how-to-avoid-damaging-your-drv8353rx-evm-with-too-high-idrive

There is quite a bit of ringing on your gates and it looks like it is causing some shoot through because the ringing is severe enough it is turning on the low side gate while the high side gate is on.

Regards,

Yara

0 Daniel Mena 6 months ago in reply to Yara Al Shami

Prodigy 20 points

Hi Yara!

Thanks for the quick reply.

I changed the IDRIVE settings for the following options.

But I still see the same ringing on the signals. Unfortunately, it doesn't seem like there was any change except for the voltage level.

I also compared the following so you can see that the behavior is almost the same.

0 Yara Al Shami 6 months ago in reply to Daniel Mena

TI__Genius 14935 points

Hi Daniel,

Daniel Mena said:
I changed the IDRIVE settings for the following options.

Do you mean you've tried all these IDRIVE settings?

you really shouldn't exceed the highlighted settings with the MOSFET you've selected:

Do you have a fresh IC you can test with?

Regards,

Yara

0 Daniel Mena 6 months ago in reply to Yara Al Shami

Prodigy 20 points

Hi Yara,

Yes. Checking the MOSFET I saw that 150/300mA and lower settings might be all right, so I tried going from GND to higher settings. Unfortunately, nothing changed.

As for the new IC, I tried with a spare PCB and used IDRIVE 50/100mA (tied to GND), but I obtained the same result again.

Next step I'll try with a previous version of the PCB that is supposed to work. Checking the PCB very quickly I saw that it also has the IDRIVE set to 1/2A so not sure why it works well in there. The schematic is supposed to be the same though. I know the major difference is the firmware (previous source code was lost) and PCB design, but still, the behavior of the driver should match the datasheet if nothing major has changed.

I'll test some more and come back to you if I find anything new. Any suggestions or additional tests are greatly appreciated.

0 Yara Al Shami 6 months ago in reply to Daniel Mena

TI__Genius 14935 points

Hi Daniel,

Have you tried any filtering components on the outputs? because it looks like the waveforms have quite a bit of noise even when the gates aren't switching.

Heres some resources that talk about RC filters

https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/991693/faq-proper-rc-snubber-design-for-motor-drivers

https://www.ti.com/lit/ta/ssztbc7/ssztbc7.pdf?ts=1739462292533&ref_url=https%253A%252F%252Fwww.google.com%252F

Let me know how your testing goes!

Regards,

Yara

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DRV8350: GHX not working properly for Synchronous 1x PWM Mode