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Electronics for CNC apparates

Last update: 31/07/2015

The STMicroelectronics couple L297 + L298 is probably one of the most popular couples to control bipolar stepper motors. Unfortunately the heating generated by the final stadium can be considered rilevant, particularly when the motor uses a current higher than 1,5A-2A/phase. A quick solution is the substition of the final dual full bridge (STM L298) with two full bridge (STM L6203).


This ic can provide a higher current (upto 5A) therefore it is possible the use of bigger motors or, using the same motors, obtain a reduction of the heat generated.

L297 L6203

The schematic is very traditional and efficient. As usual, the maximum level of the voltage as input is limited by the positive regulator (5V) therefore, in this case, the voltage is lowered by a zener and a npn transistor (tip41c) before the input of the regulator. This is necessary because the maximum input tension level is limited to 20V for a 78L05 and 32-37V for a 78H05 (but usually less and depends by the manifacturer). 
The max level of voltage can be considered around 40V.
The 0.33 2W resistor can be replaced by three 1ohm 2W resistors.
 The VRef must be regulated according to this simple formula: Vref  = Rs * Iout. In our case, with a resistor of .33 ohm and 2 amp./phase motors the value of Vref must be 0.66, quite simple.

Nothing more to say, the schematic is very traditional and follows the directives of the application notes of the ic involved

l297 l6203

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