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I am trying to drive a brushless DC motor with hall effect sensors using a microcontroller and a TI UC3625 controller.

Thing is, I haven't had much luck. Its a beast of a chip and I've tried wiring it like the "typical application" in the datasheet, I've looked at all the product notes I can find on google, etc. It seems like the suggested (possibly only?) way to drive it is by sending it a voltage.

Is this normal for a BLDC controller? I would think the standard would be PWM input. Can anyone recommend a way to get this thing working or suggest a different chip for driving a BLDC with hall effect sensors (and about 3A at 22V)?

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  • \$\begingroup\$ datasheet? schematic? This is basic research you should perform yourself, and you will get a better response if you demonstrate that you are attempting to minimize the amount of time people must spend to help you. \$\endgroup\$
    – Phil Frost
    Apr 4, 2013 at 2:16
  • \$\begingroup\$ It looks like that controller is intended for use in applications where there isn't a local MCU, which is why the control input is only analog. \$\endgroup\$ Jun 3, 2013 at 7:50

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It appears that speed control is implemented by a DC level on "Speed In" on pin 7.

They show this connected to a signal from the tachometer signal on pin 20.
It appears that if you take the 10k off pin 20 and feed a pwm signal into it that this will be smoother tp DC by the 10k and 100 NF and will apply speed controlling DC to pin 5 - which seems to be what you want. Making the capacitor or resistor larger than the 100 NF shown will smooth the DC and so stop the system hunting with PWM but will slow response to changes in control voltage level. T present time constant is 10k x 100 NF = 1 mA so you'd want say 10 kHz+ PWM frame rate to avoid jitter. Check data sheet for max allowed Rin.

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