L293D Current

Discussion in 'General Electronics Chat' started by JK-FlipFlop, Jan 8, 2011.

  1. JK-FlipFlop

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    Jul 5, 2010
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    The L293D is rated for 0.6A continues and 1.2A peak per 1 channel.
    I am searching for H-bridge with 3A peak , simillar to the L293D.

    Thank you.
    ................................................................................................
    Thank you for your answers.

    I found another driver: TC4424 (http://ww1.microchip.com/downloads/en/devicedoc/21421d.pdf)

    will it work like an H-bridge (L293D)??
     
    Last edited: Jan 9, 2011
  2. Kermit2

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    Feb 5, 2010
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  3. thatoneguy

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    The L298 is a common "Step Up" from the L293D. It has a metal tab so a heatsink may be used, increasing the current to 4A total, or 2A per full bridge/motor, with 3A peak/max current per channel.
     
  4. SgtWookie

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    Jul 17, 2007
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    The L298 is antiquated, and will dissipate a LOT of power when used near its' maximum rating. It will be very difficult to keep it cool enough.
     
  5. thatoneguy

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    L298 is the only very common H-Bridge that came to the top of the list for "Similar to L293" with peak current of 3A. The number of circuits around for the L298 is a great starting point. Similar to the LM741 as a "generic op amp", not the best at anything, but it works.

    That said, there are most likely better choices, but more information about the application is needed.
     
  6. JK-FlipFlop

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    Last edited: Jan 9, 2011
  7. Audioguru

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    A TC4425 has one output go high when the other output goes low when the two inputs are connected together. So it makes an H-bridge.
    But it has a fairly high on-resistance so it will have a very high voltage loss which will cause it to quickly overheat.
     
  8. JK-FlipFlop

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    Jul 5, 2010
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    your answer isn't clear...
    can you explain?
     
  9. Audioguru

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    The TC4425 has one inverting driver so if both inputs are connected together it becomse an h-bridge.

    The block diagram in the datasheet shows Mosfets but does not say they are the external power Mosfets so I was wrong. This IC is designed to drive two power Mosfets on each output.
     
  10. JK-FlipFlop

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    So it's good??
     
  11. Audioguru

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    The TC4425 is a good H-bridge driver IC if you connect 4 suitable power Mosfets to its outputs.
     
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  12. JK-FlipFlop

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    Jul 5, 2010
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    The driver is TC4424 (the same +-).
    can you show me schematic of the 4 suitable mosfets with this driver, it will help me alot to understand you...
    I think it will work fine without connecting somthing to the driver outputs.

    thank you very much for your time. :)
     
    Last edited: Jan 10, 2011
  13. Audioguru

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    The TC4424 needs an external additional inverter to make an h-bridge power Mosfet driver. But the TC4425 has the inverter built-in.

    In my post #9 I showed the block diagram from the datasheet that shows the driver IC driving Mosfets.

    No.
    The IC is designed to drive Power Mosfets that drive high current to the load.
     
  14. JK-FlipFlop

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    Jul 5, 2010
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    "The TC4424/5 inputs may be driven directly from either TTL or CMOS (2.4V -18V)"
    there is nothing said about anything connected to the outputs, its just driving without external compoments// or I wrong??

    The TC4424 is dual non-inverting. // its what I am looking for.....
    The TC4425 is 1 non-inverting and 1 inverting. // why do I need that??
     
  15. Audioguru

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    The datasheet says and shows that it drives external Power Mosfets, not a load. The external power Mosfets drive the load with as much power as you want.

    An H-bridge has one output go high when the other output goes low then it alternates. Only the TC4425 does that. The TC4424 needs an additional inverter to do it.
     
    Last edited: Jan 12, 2011
  16. JK-FlipFlop

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    Jul 5, 2010
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    Ok thank you.

    TC4424 is the one I need because it is like full H-bridge for controlling motor direction. (2 directions by the inputs 1-0 / 0-1 stop = 1-1,0-0). The L293D is non-inverting too///

    About the external mosfets, I dont need them I just want to drive a motor (12V 3A peak current) so my major Quistion is will it work like a regular H-bridge????
    if yes so this driver solves the low current (1.5A, I need 3A) of the L293D H-bridge.....
     
    Last edited: Jan 11, 2011
  17. Audioguru

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    The TC4424 needs two inputs for forward, reverse and stop.
    The TC4425 neds only a single output for forward and reverse but cannot stop.

    The tiny IC will overheat if it drives a load. It is designed to drive power Mosfets that drive the load.
     
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  18. JK-FlipFlop

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    Jul 5, 2010
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    but it can drive up to 3Amp?? so why not?
     
  19. Audioguru

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    The title of the datasheet for the TC4424 and TC4425 is Power Mosfet Driver, not motor driver.
    Its output resistance is 8 ohms when hot with an 18V supply and is higher with a lower supply.
    If its output resistance is 10 ohms then a load current of 3A will cause 90W of heat. Two outputs will cause 180W of heat.
    But the tiny IC will be at its max allowed temperature with only 1W of heat.

    It is designed to have an output current of 3A only for 25ns to 60ns while it charges the input capacitance of a power Mosfet.
    With an output resistance of 10 ohms and 1W of making heat then the continuous allowed current from a single output will be only 315mA and the continuous allowed current from two outputs is only 158mA each.
     
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  20. JK-FlipFlop

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    Jul 5, 2010
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    Thank you very much for the information and your time, but I have one last quiston: what is the difference between this driver outputs resistance to the L293D outputs???? and why the L293 doesn't heat like the TC4424??
     
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