DRV8432DKD

Thanks a lot for your nice reply.

But mentor graphics expedition i searched is not available for student.can you tell me where can i get the file where i can download mentor graphics expedition.

Waiting for reply.I know this is not related to your profession.But if know then please tell me.

Vipin Patel

To Mr Ryan Kher,

THanks a lot for your concern.I got it from our Institute.

I Have One Doubt Regarding Dead Time of DRV8432:

In One of the TI community it is written that we have to control the dead time of DRV8432.

What i think is as follows:

About Dead Time:

But , See if we give PWM_A then how we can control the dead time.Because this signal will be feed to  half bridge_A  it should be internally controlled.Because dead time is between high side gate driver to low side gate driver of the same half bridge.Suppose duty cycle is 50% then for 50% time high side gate driver should be on (and low side should be low)and for 50% low side gate driver should be on(and high side should be low)and dead time should be given in this time only,then how we can control it from outside.

Please let me know where i am going wrong.

If you have waveform of the same for your explanation it will be great help for me,to avoid my dc motor damage as  well as IC will go bad if i control in wrong method.

Parallel Mode Drive:

Current Sense:

Can i put resistance of say 10m ohm  in series of motor to measure the current and control the torque of a brush Permanent Magnet DC motor. Does it will effect the switching of half bridge What are the other thing i have to take care.Please let me know.

If i can put then what are the disadvantage i have to face.It is the same Rsense_AB or Rsense_CD mentioned in datasheet.Does it put for that purpose.If yes then why two Rsense is required.Can it not be done with single resistance.

Waiting very eagerly for your reply Mr Ryan Kehr.

With Regards,

Vipin Patel

CEDT,Bangalore

Vipin,

I am not sure where you saw "dead time" control is needed for the DRV8432.  As you expected, there is NO way to control the dead time externally on the DRV8432.  You need independent control of the FETs which you do NOT have with the 8432.  You might have read something regarding the 8301 in which case you can control the dead time.

In terms of your question regarding a PM DC motor, you should look at the DRV8312 device or DRV8332 (same general current handling capability as the 8432).  We have a released kit, DRV8312-C2-Kit that has all the software, schematic, BOM including documentation on how everything works.  You can also explore our motor site with videos,etc. on different control techinques including sensored and sensorless. 

To answer your question directly, you can use inline current sensing as you suggest and that is what they are for in the schematic.  BUT, if you only want to use one current sense resistor than I would suggest connecting all the ground points together into a single low-side current sense to GND.  If you check out our kits, you will see this. 

www.ti.com/motors

To,

Ryan Kehr

Thanks for your fast and nice reply.

As you are suggesting for PM DC motor ,we should use DRV8412 or DRV8332 instead of DRV8432.But our current requirement is 13A continuous current.So,i planned to use drv8432 in parallel mode so that i can get max of 14A.But DRV8412 is not having this much current capability right.DRV8412 is having 6A continuous in parallel mode.

My motor specification is as follows:

24V,320W PM DC Motor

Speed(at 22Nm) 120rpm

torque(load):22Nm

torque(No load):60Nm

For this motor can i use DRV8412 or DRV8332 for maximum power.Or DRV8432 is best option.Can you tell me what are the issue in DRV8432 using for above motor.

If i am wrong let me know.

As you ask about which forum i read the above information is as follows:

Community name:DRV8432 written by Steve Crump and verified by Don Dapkus I think they are TI employ right.

message is as follows:

Ron, we hope to release DRV8432 EVM by the end of this year, but by end of January at the latest.  You might ask your local TI sales office if they can get an EVM for you now.  In the meantime, DRV8412 EVM is available.  DRV8412 is similar to DRV8432, just lower current (2 x 3A continuous, 2 x 6A peak, but no heatsink is required).

DRV8412/32 follow PWM inputs directly, so you will need to insert required dead time.

DRV8412/32 half-bridge grounds are brought out independently and may be grounded through low-value (5 to 10 milliohm) resistors for current sensing.  Rev E and F EVMs, the current versions, include the resistors and current sense amplifiers following them.

Regards,

Steve.

With Regards,

Vipin Patel

CEDT,IISc Bangalore

Dear Mr Ryan

What is the max power dissipation of drv8432dkd if i am using it in parallel modeI am drawing 14A max(7A from each hafl bridge).Can you guide me in selection of heat sink for this device.

I check your discussion you suggested heat sink of 4.43  deg C thermal resistance.

Please see my calculation where i am going wrong please tell me

Maximum power dissipation Calculation:

P=V x I

V is voltage across each mosfet when it is on.In data sheet it is given as when we draw 7A it will be around 1.2V.

Power P=1.2x7=8.4W for each mosfet.But in parrallel mode 4 has to be on.therefore disspation will be

Total Power dissipation=8.4x4=33.6~40W(i have taken for save case)

maximum juntion temp=125 deg C

Maximum Ambient temp=50deg C

thermal resistance of paste as you mentioned in datasheet .I seen the datasheet of those paste .it come around 0.03deg C/W

Depending upon above data and below equation thermal resistance of heat sink is coming around

RJATotal =RJC+ RSA + RCS

RJC=0.9 deg C/W

RCS=0.03deg C/W

RJATotal=125-50/40=1.875 deg C/W?

Therefore, for heat sink thermal resistance is coming around

 ?SA =0.945 deg C/W

Can you guide me where i am going wrong

With Regards

Vipin Patel

IISc Bangalore



 

Sorry For the Same...

Whatever datasheet you have given its rms current is 5A So it is not for drv8432 but for drv8422.My doubt still remain the same according to the calculation you did for 5A

i did it for 7A for drv8432.For DRV8432DKDEVM you made it for 7A right.But whatever you send is for 5A.Whatever calculation you have given i did it for 7A it is not matching the

heat sink criteria which you preferred for DRV8432EVM.What is the reason can you tell me where i am going wrong.

You have selected heat sink of 4.43 deg C/W which is not suited as per above calculation.How you reach to 4.43 dec C/W.

With Regards,

Vipin Patel

IISc BAngalore