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adp3624 malfunction at about 1A

Question asked by JanLichtenbelt on Aug 19, 2014
Latest reply on Aug 29, 2014 by JanLichtenbelt

I developed a RC speed control for DC motors. It took me about 2 years to get it finished and recently it has been published in Elektor 2014 7/8 p104. The PWM pulses are generated by a microchip PIC12F1840 and directly connected to both input of the ADP3624 bridge (INA and INB). The output shutdown (SD) connected to GND and the OTW is used in the microchip to control the PWM pulses. The PCB layout for the ADP3624 with 2 capacitors 100 nF and 10 uF is the same as given in datasheet of this bridge.

So far so good. I tested the project with a model train DC motor of about 300 mA with a lead battery (12.6V) as power source. But now I’m testing a second train with 2 motors with about 400mA. But after a while or at higher traction (higher currents about 1A) the output of the ADP3624bridge give a malfunction. On a scope it is seen that normally the PWM voltage is between 0 and 12.6V, but during the malfunction the voltage is lowered to -3V to 9Volt within 1 msec during 12 msec and then no PWM is seen anymore. This repeats with some frequency depending on the motor load.

During this malfunction the OTW rest unchanged.

Can you help me?

 

Kind regards

 

Jan Lichtenbelt

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