Function description and application information

SPMD150STP

14/23

Doc ID 17160 Rev 1

Figure 12.

VREFA and VREFB internal connection

The voltage at VREFA and VREFB can be supplied in two way:

●

Using an external source (see Figure 13), driving VREFA and VREFB pins together or

separately as in the micro-stepping mode (i.e: a micro-controller fixes a variable voltage

to get variable current in the stepper motor phases).

Figure 13.

VREFx from an external source

●

Using the module reference voltage source, REF (pin2) (see Figure 14), which supplies

1.225 V. The REF pin has a 10 k

Ω resistor in series, take that in account during design.

●

In this case a proper resistor Rx must be connected between REF and GND1, VREFA

and VREFB will be connected together to REF pin (see Figure 14).

Use following equation to calculate Rx: