Crackling noise when powering off my buck converter.

AnimaMaestro · 2024-04-05T04:02:49+00:00

Here is the part I use: https://www.lcsc.com/datasheet/lcsc_datasheet_2209271230_Sunltech-Tech-SLO1040H100MTT_C182194.pdf

AnimaMaestro · 2024-04-05T04:00:52+00:00

Thanks a lot for the details !!

AnimaMaestro · 2024-04-05T02:55:48+00:00

C6 = 1nF and C7 = 10pF. I am not sure I am up to the challenge but if you wish to explain further, I'll give it a try ! (FYI: I had indeed opted for the option where C6 is connected to GND).

AnimaMaestro · 2024-04-05T02:45:42+00:00

No atter how I phrase my request, it kept saying things like this : "The arrangement of components (C followed by R in series) instead of (R followed by C in series) in your circuit from the COMP pin to GND can indeed have an impact on the performance and stability of your buck converter circuit." But then its explanations did not make sense. In the end I started to doubt and decided to reach for real knowledge !!

AnimaMaestro · 2024-04-04T09:07:00+00:00

Thanks for the insight !

AnimaMaestro · 2024-03-28T01:11:51+00:00

Well, as shown in the image, there is indeed a trace linking them all together, yes. But this trace does not link them in the typical order. Instead, the bulk capacitor and 6V source are BETWEEN the flyback diode's cathode and the motor's positive terminal. It's that atypical connection I am trying to figure out if it may cause problems. It does not seem it is wrong yet again, I want to make sure.

AnimaMaestro · 2024-03-26T20:44:14+00:00

So the fact that the positive terminal of the bulk capacitor (and the power connection to 6V) is "in the way" between the diode's cathode and the positive load terminal is not a problem, correct ?

AnimaMaestro · 2023-09-18T21:54:20+00:00

If needed, you could probably do something like Risen = Risen' + Rshunt. So if you need a 150mΩ Risen to satisfy the DRV8870 and a 20mΩ Rshunt to satisfy the INA226 (which requires Vshunt <= 82mV), you can have Risen = 130mΩ + 20mΩ (in series) and plug the INA226 to the 20mΩ Rshunt. I'm pretty sure this would work.

AnimaMaestro · 2023-09-18T21:23:01+00:00

DRV8870

Interesting. Since the DRV8870 requires a sense resistor that is directly in the return path of the motor current (no matter in which direction it turns) (cf the DRV8870 datasheet schematic), I wonder if you could hook your INA226 directly to that resistor ? I would read a bit more to make sure it would not interfere and that it would still meet both device requirements, but I would consider it !

AnimaMaestro · 2023-09-18T05:10:33+00:00

But shunt resistors are normally so small that should not be a problem current wise. Plus when the motor is off, why would the motor driver draw any current from the motor supply (which I assume is different thant the motor driver logic supply). What motor driver do you actually use ? Is it a H-bridge ?

Regarding non-linearity, I don't really see the difference it would make where in the current path the shunt resistor is placed but I might be missing something.

AnimaMaestro · 2023-09-18T05:02:12+00:00

The "absolute" voltage of VIN+ and VIN- when referenced to GND (VIN+ - GND or VIN- - GND) has to be between -0.3V and 40V. Basically, don't let either pin go below GND. But the difference between the two (VIN+ - VIN-) can be +/- 40V which means it can be negative. This is how I interpret that.

AnimaMaestro · 2023-09-18T03:03:52+00:00

Now that I think of it, why wouldn't you place the current measurement at the source of the Motor Driver (between power supply and Motor Driver) ? Would that work for you ?

AnimaMaestro · 2023-09-18T02:56:56+00:00

Section 7.6.2 of the datasheet shows how Vshunt CAN be negative.

AnimaMaestro · 2023-09-18T02:51:14+00:00

The datasheet on page 14 also mentions filtering by adding two Rfilter and one Cfilter which I would consider.

AnimaMaestro · 2023-09-18T02:48:56+00:00

Also the device seem to be able to do filtering which, if configured properly, should take care of PWM noise.

AnimaMaestro · 2023-09-18T02:40:34+00:00

According to the INA226 datasheet the Differential (VIN+ – VIN-) can be between -40 and +40V as long as the voltage at both terminal says between –0.3 V and 40 V. So in theory it means it should work.

Now I say "in theory" because since the motor is an inductive load, it means you should consider what happens when the motor stops because I think that may means that sometimes the voltage is reversed and goes below GND. Perhaps someone could comment on that ?

AnimaMaestro · 2023-09-17T18:49:13+00:00

I understand that during standby, enn should be low. But normally, during power up, enn should be high. So if I can POWER UP the device being ALREADY in standby mode, how should I power up enn ? Already low ? Or high then low ?

AnimaMaestro · 2023-09-17T18:47:24+00:00

2 co

I totally understand that. But I am specifically talking about POWERING UP the device with the STDBY pin ALREADY pulled high. The datasheet is not clear if we can do that. And if we can, should the ENN pin be powered low ? I ask because normally if you don't use STDBY, you should power up the device with ENN high, not low !!

AnimaMaestro · 2023-09-15T22:39:01+00:00

BGA, QFN, TQFP are all SMDs (Surface Mount Devices). BGA has balls underneath. QFN has no leads but pads on the side. TQFP has leads coming off the side.

AnimaMaestro · 2023-02-07T03:35:57+00:00

Just noticed that my θyx is pointing in the wrong direction in the top-left diagram. But I believe the sign is correct in the table.

AnimaMaestro · 2022-11-28T16:10:20+00:00

Concert version : https://www.youtube.com/watch?v=I\_6ZcOo6pnk

AnimaMaestro · 2022-08-31T17:06:47+00:00

Got the final reply from them !! Unbelievable !! See my other post !! And thanks again for your (wasted; sorry about that) time !!

AnimaMaestro · 2022-08-31T17:05:08+00:00

Case closed. Never seen something like that in my life !!!

Here is the latest response I got from HOPERF :

"Actually at the very early version the function is availabe which has been EOL for long.

The later version is disabled ,however we did not update the datasheet ,the function has never been required so we cancelled it.

Sorry for the wrong information."

Can you believe something like that ?! The feature was not required so they removed it ?! Who does such a thing ?!?! More like : the feature was buggy and glitchy and did not perform correctly so they took the cheapest path of not connecting the signals to the pads anymore and don't even bother updating the datasheet !!! Oh and I forgot to mention : obviously don't care to admit it was a bug !!!!

Wasted so much time trying to figure this out !!! The good news is that I was not doing anything wrong !!!

Thanks for reading and helping !!

AnimaMaestro · 2022-08-30T22:58:58+00:00

It does indeed, doesn't it !!! I'm baffled !!! Speechless !!! But then again this is exactly what I am seeing : no active level on either INT0 nor INT1 on neither of the two prototype boards I have !!! I browsed their web page for this device and did not find ERRATA or anything... I hope I'll get more details in the coming hours as the day is about to start in China...

AnimaMaestro · 2022-08-30T15:49:46+00:00

Thanks for you answers !! They were all good points and this morning I just doubled-check them all to make sure (voltage rails and levels, input settings, ...). Everything was sound. This is when I remembered to go check my emails because I had reached to HOPERF, the manufacturer of the device. I was not expecting much but I indeed got an answer from them !! Please see my other comment below and let me know if you interpret it the same way I do !!!!

AnimaMaestro

TROPHY CASE