ST L6506

The L6506/D is a linear integrated circuit designed to sense and control the current in stepping motors and similar devices. When used in conjunction with the L293, L298, L7150, L6114/L6115, the chip set forms a constant current drive for an inductive load and performs all the interface function from the control logic thru the power stage. Two or more devices may be synchronized using the sync pin. In this mode of operation the oscillator in the master chip sets the operating frequency in all chips. The L6506 is intended for use with dual bridge drivers, such as the L298, quad darlington arrays, such as the L7150, quad DMOS array such as L6114 - L6115, or discrete power transistors to drive stepper motors and other similar loads. The main function of the device is to sense and control the current in each of the load windings. A common on - chip oscillator drives the dual chopper and sets the operating frequency for the pulse width modulated drive. The RC network on pin 1 sets the operating frequency which is given by the equation torand Vref. Since separate inputs are provided for each chopper, each of the loads may be programmed independently allowing the device to be used to implement microstepping of the motor. Lower threshold of L6506's oscillator is 1/3Vcc. Upper threshold is 2/3Vcc and internal discharge resistor is 1 KΩ ± 30 %. Ground noise problems in multiple configurations can be avoided by synchronizing the oscillators. This may be done by connecting the sync pins of each of the devices with the oscillator output of the master device and connecting the R/C pin of the unused oscillators to ground. The oscillator provides pulses to set the two flip - flops which in turn cause the outputs to activate the drive. When the current in the load winding reaches the programmed peak value, the voltage across the sense resistor (Rsense) is equal to Vref and the corresponding comparator resets its flip - flop interrupting the drive current until the next oscillator pulse occurs. The peak current in each winding is programmed by selecting the value of the sense resis

• The circuits use the L6506 to implement constant current drives for stepper motors.
• The L6506 may be used to implement either full step or half step drives.
• The L6506 may also be used to implement microstepping of either bipolar or unipolar motors.