The L297 integrates all the control circuitry required to control bipolar and unipolar stepper motors. 

Used with a dual bridge driver such as the L298N forms a complete microprocessor-to-bipolar stepper motor interface.  For example The L297, takes the signals from your microprocessor and translates them into stepping signals to send to the L298 which actually drives your stepper motor. The L298 is capable of driving up to 2A per coil. 

One interesting feature of the L297 is its current sensing and 'chopping' abilities. The L297 will sense the amount of current flowing through the coils, and will 'chop' the signal to the L298 so that the average current flowing is the desired amount. You can configure this current by setting the trimpot on the board and measuring the voltage on the test point.

For L297 Datasheet, please click here

For L297 Application notes, please click here