h-bridgehow-does-it-work
The BTS7960 H-brige has 6 pins (excluding current warning pins).
I usually connect all the "Enable" pins to HIGH and only use the PWM pins to control the motor speed and direction. That works perfectly, but is that a good practice?
Are the "Enable" pins really unnecessary or am I missing something?
You will experience some significant performance issues if you were to use the EN for PWM.
If you look at the datasheet, especially the part you provided in the OP:
the EN pin doesn't just stop sourcing/sinking power (ie the FET's are not gated), it creates a "Fast motor Stop" condition which basically means BothTop or BothBottom switches are enabled. This essentially shorts out the machine windings and it rapidly stops the rotor.
As a result if you were to use such a pin for PWM you would be continuously stopping
You need to drive one of the direction lines (E or F) high at the same time that you drive the corresponding PWM line (G or H, repsectively) high. These two signals are effectively ANDed together by how the driver chips are wired together. My guess would be that E and F control the two high-side switches (one on each chip) and that G and H control the two low-side switches.
Best Answer
If you don't need the enable pins, there is nothing wrong with tying them high. Just because they are unnecessary in your design, doesn't mean they are in some other design.
The purpose of the pin is to allow both transistors in each half-bridge to be turned off. The
PWMpin (calledINby the datasheet) is used to select whether the high or low transistor is on, whist theEnablepin (calledINHby datasheet) is used to switch of both transistors.If for example you wanted the motor to freewheel (soft breaking in @vicatcu's answer), you would need to turn off both high and low sides, leaving the motor current to flow through the diodes in the bridge. If you want to stop the motor instantly (hard breaking), you switch both h-bridges to the same transistor (both high, or both low).