drv8402 problem again- old thread doesn`t work

Miro,

With /FAULT at low, this explains the non-operation you seeing.  Let us figure out what is happening here first. 

1)  What is the status of /OTW?  If this is low, then you have an over-temp condition.  

2)  You have RESET_xx going off the schematic, but I assume you are holding these terminals HIGH?  

3)  Other reasons for /FAULT being low would be over/under-voltage conditions on the internal voltages.  Please probe all of the GVDD_x, VDD, and VREG pins (VREG = 3.3V).  Also check the PVDD_x pins.  

4)  Put a 8 ohm load on the device and see if device operates normally after power cycling.  It could be that you have excessive peaking in the output inductor without a load and this would cause an over-current fault to be reported.  

Regards,

Ryan

1) /OTW is low, too. Don`t know why, because system doesn`t work, so there shouldn`t be a overtempereture (i think). Should i connect some resistor  to be able to probe /otw and /fault without connecting to MCU? I dont know if there is any internal resistor in drv8402, i must find app. notes or smthing.

2) yes

3) GVDD_x, VDD checked, but VREG looks like connected to GND, doesn`t it? Like in the scheme. I will probe it next time...

4) i have connected an DC motor, it doesn`t help, but i will try it with 8 ohm.

Thanks

Miro,

VREG is a regulated 3.3V output.  The device regulates this voltage off of VDD.  You have a decoupling capacitor to GND according to your schematic, so you should measure 3.3V on that pin.  If you don't, there is a problem with the device or a short on the board.  If VREG is low, it would explain the /FAULT and /OTW being low as they are internally pulled up to VREG.  You can see this in the pin description table on the datasheet.  

Also, do you have a heat sink connected on top of the device?  How much current do you plan to drive in your application?  Even with light loads, the device will heat up significantly without some heat sinking on top of the device.  The interface on the top of the device is the only path to transfer heat out of the package.  

Regards,

Ryan

Ok i will probe it. About heatsink, iam plannig to have one, a big one. Because i will drive about the maximum , teoretically to 5A per bridge, so 10A through device. But first thing first, device must start working with test conditions - lower current for a short period of time, avoiding the overtemperature, doesn;t need to drive maximum current finally.

After some more probing i will post again.

Many thanks.

Regards

Miro

Ryan,

so after some time i`m posting again. I was making a new pcb with second sample of drv8402, because the old one got Vreg and GND connected internally. After few minutes of testing of new pcb i`ve got #otw, #fault and Vreg pins low, and Vreg is internally connected with gnd.

What now? I thing a i`ve damaged another unit...

Miroslav,

At this point, I think it is best to remove the part and check all the connections on your board.  Verify that the VREG connection is not shorted to GND by checking impedance.  It is possible that the decoupling capacitor has shorted.  Please check all of the other connections to your schematic before installing a fresh DRV8402 sample.  

Are you using a heat sink on top of the package?  If so, what interface material are you using?  If you use an electrically conductive paste, this could be bleeding out (if too much was used) onto the pins and causing a short. 

These are the steps I recommend to debug the problem.

Regards,

Ryan

Ryan,

vreg with gnd is shorted, decoupling capacitor is not shorted. All connections on board seem ok. Is it possible when my MCU is connected wiht drv4802 and i`m writing to memory of MCU throuhg Jlink  that something happens through pwm to drv8402?

Regards,

Miro

Miro,

Did you remove the device?  Please remove from PCB and check the pad on the PCB to GND on VREG terminal.  What is the voltage on your microprocessor?  Are the PWM outputs referenced to 3.3V?

It would be good to check operation of the NEW device you put down on the PCB after checking all PCB connections BEFORE you send PWM.  Please take a step-by-step approach to solving this problem and eliminate the variables along the way.

Step 1: Remove damaged device.

Step 2: Check all connections on PCB by measuring with DVM the impedance between the pads on the PCB and GND.

Step 3: Install new device.

Step 4: Power up new device with NO PWM from micro and device held in RESET.  Connect RESET_AB and RESET_CD to GND.  VREG should equal 3.3V at this point.  Bring the device out of RESET.  Check again.

Step 5: Put a scope on input PWM and output PWM why brining up MCU.  

Regards,

Ryan

Ryan,

that were my steps when i was `bringing to life` last unit . PWM of MCU is referenced to 3.3V. The few minutes, when it worked,  the Vreg was 3.3V  and I boot up the device with Reset_ pins connected to GND, than bring them to HIGH. #OTW and #FAULT pins were HIGH, too. Then I started to program MCU and its pwm duty cycle and drv8402 went down...

Regards

Miro

hi,

i am using same schematic which are given in datasheet as well as urs schematic u have posted. i am using 10 k ohm instead of motor for checking purpose.

 i also facing same problem like you. i am getting DC voltage at output but i want ac voltage at output..

how can i get it?

I am going to need some more information to help you solve this.

1)  Is /FAULT low?  Is /OTW low?

2)  Check VREG voltage, is it 3.3V?

3)  Are /RESET pins pulled up to 3.3V?

4)  What are your voltages at GVDD/VDD/PVDD?

5)  What mode are you operating at?  

6)  Do you have some scope captures of the PWM inputs and outputs (measured directly on output pins)?

FAULT and OTW is low

VDD and GVDD is +12v

PVDD is +20V

M1 M2 M3 is 0

so output should be 0 to 20 V? right

i didnt connect the rset pin

VREG is 3.3 v

Anurag,

The /RESET pins should be pulled HIGH...connect to VREG.

when i give PVDD voltage around 20 V.

lots of current its pulling. why?

other wise circuit is going fine

what will be the GVDD if i give PVDD 18V?

please help

it make me really confusion

what r external voltage should give to DRV 8402?\

GVDD and PVDD should be 2 different source right?

Anurag,

GVDD is the supply used for logic and the gate drives, and should be nominally ~12 V. PVDD is the supply for each half bridge and can be up to 50 V.

Thanks,

Matt

Thank u so much

i am using heat sink but the IC become so hot why?

Anurag,

The IC is intended to warm up; is it possible for you to measure the temperature?

Thanks,

no, i cant measure it but i can say that it almost burn the finger if i touch it

Anurag,

May I see your schematic?

Thanks,

Matt

i  am doing Schematic design which is back of  DRV 8402 datasheet

Page 12 ... Full Bridge Mode Diagram

Anurag,

Sorry for the delay; how much current are you supplying to each motor? Following the application specified should not cause any problems on its own.

Thanks,

Matt

i am giving PVDD is 20v and GVDD is 12 V

and also 2 square wave of opposite phase around 0-4v

Anurag,

1) Can you reduce the PWM amplitude to ~3.3 V? I want to see what happens. Also, are all four of these PWM inputs set to this 0-4 V square wave?

2) Are you observing any output from the DRV8402?

Thanks,

Matt

i am using only PWM C and PWM D as input and checking an output across the resistor which connect at output C and D......

i am giving square wave to input PWM C n PWM D...

 I am getting peak - peak only 752 mv at output

Anurag,

Please double check that you have installed the part on the board in the right orientation.  There is a small circle with lines through it that marks pin 1 of the device.  Please make sure this aligns to pin 1 on your board. 

I only ask because we have had this problem many times before. 

BTW, we just releasd an EVM for the DRV8432EVM.  It will be available to order on Monday.

http://www.ti.com/tool/drv8432evm

my professor say that if i give 20 V to PVDD then at output i should get Peak to peak 20v

that means DC change to AC

its not happening.. i am only getting peak to peak 760 v

alignment is ok  At pin 1 connect to 100nf and10uf to GVDD

alignment is ok

Can you send a picture of your board, layout files, and schematic? 

give me ur email id so that i can send pic

Please just insert here in the forum.  Click on the little "paper clip" icon to insert any file. 

i think i burn the chip

PVDD is pulling lots of current

Anurag,

Based on your previous posts, I'd agree with you that the IC is probably dead.

Thanks,

Matt