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Question

Hi,

I have a couple of questions regarding the PmodHB5.

How fast can I control the Pmod Hb5 activation pin?
In the reference manual (page 2),there is an example with a 2 kHz and 50% duty cycle.
Is it possible to drive that pin at a rate higher than 2 kHz? If yes, what is the highest rate?
How fast can I switch on and off the transistors of the Pmod Hb5?
Is it possible to have the datasheet of those transistors?


Thank you.

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5 answers to this question

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Hello @herve,

 

I consider that it's much easier for you, to personally look trough datasheets and see if HB5 fits your needs. So, for Pmod HB5 we used these transistors:

- For Q1:    NTHD4508NT1, On-Semi Power MOFSET, 20V, 4.1A, Dual N-Channel               
- For Q2:    NTHD4401PT1, On-Semi Power MOSFET, -20V, -3.0A, Dual P-Channel

From my understanding the enable pin (activation) is driven by transistor Q3.  The part number for this transistor is MBT3904DW1T1. I hope my answer gives you a solution.

 

Best Regards,

 

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Hello  @BogdanVanca

Thank you for your reply with part numbers. There is still one opened question without answer.

I still need to clarify if it is possible to drive the enable pin at a rate higher than 2 kHz? If yes, what is the highest rate?

I looked through the datasheet, but I there is no details about the highest rate one can drive the enable pin.

 

Thank you

Kind regards,

H

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I'm sure it's possible to "drive" it at any rate. What I don't know is the amount and color of the magic smoke coming out :-)

This is a fairly basic power electronics question: Each switching event dissipates energy because there is voltage across the transistor while current is nonzero. The question is, how much energy dissipation can you tolerate.

With a 2A transistor you can probably feel with your finger whether or not it runs hot.

In similar applications, PWM frequencies of 15 kHz or more are possible (search for "brushless ESC") but I doubt the motor will run any smoother.

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I think this nicely sums up the trade-off:

3) average coil current

vs

4) switching losses

if efficiency matters.

There's actually an interesting observation if I listen to any (modern) subway or railroad engine starting up: they control the converter switching rate depending on RPM to manage 4) for the high current at startup. Some Austrian railroad company is actually making fun of it and plays an ascending melody through the converters on departure...

 

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