• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 31 subscribers
  • Views 1403 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV8844

WILLIE MCCAIN1
Intellectual 380 points
Other Parts Discussed in Thread: DRV8711, DRV8844, DRV8800, DRV8801, DRV8412, DRV8848

ON THE ABOVE I WOULD LIKE TO NO , THAT CAN THE PART BE PARRALLELED TO INCREASE OUPUT POWER AND IF I HAVE LETS SAY 5 UNITS ON THE SAME BOARD ALL PINS ARE PARRALLELED INPUTS AND OUTPUTS AS WELL SHOULD I USE A SMALL INPUT RESISTOR ON ALL OF THE INPUT LINES EVEN THOU THEY ARE SHARING THE SAME SIGNALS( IN1 THRU IN4 LETS SAY A 1 K OHM IN SERIES WIITH ALL THE LINES , I MEAN IF I HAVE FOUR UNITS ON THE BOARD ALL INPUTS WILL BE BUFFERED BY A 1K, SO THATS 16 PCS TOTAL )  ENABLE EN1 THRU EN4 ALL LINES TIED TOGETHER WITH ONE 1K RESISTOR . , THE FAULT PINS EACH UNIT WILL HAVE A 10 K PULLUP , ONE PER DEVICE SO YOU WILL HAVE 4 10K SO CONTROL OF THAT DEVICE THAT FAILED ARE HAS A FAULT CAN BE HANDLED, ALL UNITS WILL HAVE A .1UF CAP FROM  THE VCP PIN TO THE BUS VOLTAGE EACH UNIT WILL HAVE A 10UF CAP AS CLOSE AS POSSIBLE TO EACH UNIT.

ALL OUTPUTS WILL BE BUFFERED WITH A .1 OHM 3WATT CURRENT SENSE RESISTOR IN SERIES WITH EACH OUTPUTAND THAN ALL THE OUTPUTS ARE GROUPED TO THE SELECTED TERMINAL FOR FORWARD AND REVERSE OPERATION.

THE SLEEP AND RESET PIN WILL BE PULLED HIGH WITH A 100K RESISTOR AND THE TERMINALS CAN BE TOGGLED TO SHUTDOWN THAT DRIVER IF A FAULT CONDITION APPEARS.

THIS WILL BE A SINGLE ENDED APPLICATION WHERE THE BUS VOLTAGE WIIL BE 35 VDC MAX AND 27.5 VDC NORMAL AND 21.5 VDC WILL BE THE LOW VOLTAGE BEFORE THE VOLTAGE COMP SHUTDOWN ALL CONTROLLERS ARE THE POINT OF WHERE THEY ALL TURN ON .

ONCE THE BOARD IS BUILT UP A .200" THICK GAP PAD WILL BE PLACE ON TOP OF THE DRIVER DEVICES AND THE HEATSINK ON THE TOP OF THAT FOR THERMAL TRANSFER AWAY FROM THE DRIVER BOARD

THE PWM WILL VARY FROM 0% TO 100% / ARE 5% BEING MIN AND 95% BEING THE MAX THE PWM FREQ. WILL BE 50KHZ MAX, WHICH THE PWMS SIGNALS WILL SWITCH AUTOMACALLY FROM FRD. TO REV ARE FROM REV. TO FRD. 

THIS APPLICATION WILL BE FOR TEST FIXTURES THat will test aircraft actuators wher the unit will have a brushed dc motor are brushless type, and drive actuators to full extend are full retract posistion

let me no 

thanks

  • 0
    TI__Guru** 114905 points

    Hi Willie,

    We do not recommend connecting the outputs in parallel. 

    Are you trying to create a 50A driver? If so, please take a look at the DRV8711. It is a predriver and can be connected to external FETs that driver much more current.

    If you are trying to do something else, please specify what your voltage, current, PWM inputs, and any other required information. We can help suggest a device that may better fit your needs.

    For reference, please look at the links below:

    http://www.ti.com/lsds/ti/amplifiers-linear/integrated-motor-driver-products.page

    http://www.ti.com/lsds/ti/amplifiers-linear/3-phase-brushless-pre-driver-products.page?paramCriteria=no

  • 0 in reply to Rick Duncan
    Prodigy 40 points

    Hi, can you clarify why you do not recommend connecting the outputs of the DRV8844 in parallel?

    I actually planned to do just that, to try to drive a low-inductance load at 30kHz+ [peltier module]

    DRV8844 seems great because I want to use a 48V supply (it's 60V safe), I can run my 2mA MCU with the 10mA  3v3 LDO,  and I don't really see an alternative chip from TI that's better suited.  DRV88412 looks maybe OK though the limit is 52.5V, but it doesn't have a 3v3 LDO.

    (1) Can you clarify the statement
    "We do not recommend connecting the outputs in parallel."?


    (2) While I am at it, I should ask a quick practical question I do not see information on the datasheet for.  I intend to tie nReset and Sleep to the 3v3 output, but I'm not entirely sure if that will be enough to power my device when I attach the 48V powersupply to VM and Vneg.  I don't know if the 3V3 output will immediately turn on, since it needs the nReset and Sleep to be high, but I am using it to drive those high. 

    Thank you very much.

  • 0 in reply to Tomek Brzezinski
    TI__Guru** 114905 points

    Hi Tomek,

    Tomek Brzezinski said:
    (1) Can you clarify the statement
    "We do not recommend connecting the outputs in parallel."?

    The DRV8844 was not tested to support parallel. We have tested some of devices and describe the connections in either application notes or the datasheet.

    An example is the DRV8800 and DRV8801. The app note ( LINK ) describes this. Other devices like the DRV8412 and DRV8848 have the description in the datasheet.

    Tomek Brzezinski said:
    (2) While I am at it, I should ask a quick practical question I do not see information on the datasheet for.  I intend to tie nReset and Sleep to the 3v3 output, but I'm not entirely sure if that will be enough to power my device when I attach the 48V powersupply to VM and Vneg.  I don't know if the 3V3 output will immediately turn on, since it needs the nReset and Sleep to be high, but I am using it to drive those high. 

    The 3V3 output should immediately turn on. The datasheet states on page 9 that "The V3P3OUT LDO regulator remains operational in sleep mode."

  • 0 in reply to Rick Duncan
    Prodigy 40 points

    Ah! I see. So The DRV8844 is not explicitly tested for parallel use. Lacking an understanding of the way chip manufacturers work/explain their chips, does that mean that it explicitly has a problem with parallel usage?  It seems to me that if it worked out of the box, you would say something like "works, just at lesser performance" or something like that. Or "works, but don't expect the full PWM frequency range"

    None of the other chips you mentioned have the voltage limit near what I'm looking for, so I'm inclined to still *try* paralleling the outputs, while recognizing that it might not work that well. I just would very much appreciate an answer like "No, it definitively will fail" if you know that to be a likely situation.  My load needs are relatively conservative; I don't expect average current over 2A, though peak current will be a good bit higher. I hope to filter that so that it may not be too much of an issue [I'm driving with low ~15% duty cycle - effectively I need this to be a dual direction [bipolar?] switching supply, in a manner of speaking.]

    I am further encouraged by another user on this forum in some post saying in an offhand way "you can parallel the DRV8844" or something like that, but it was not clear whether he or she knew that from first hand experience or was just guessing.

    An extra thanks for letting me know about the 3v3 LDO output, I must have missed that when I was reading the datasheet! Very helpful to know.