6

Functional description

PWM current controllers and a power stage composed of two fully-protected full-bridges.

6.1

Standby and power-up

threshold.

When the device is in standby status, the power stage is disabled (outputs are in high impedance) and the supply

to the integrated control circuitry is cut off. When the device exits the standby status, all of the control circuitry is

reset to power-up condition.

At power-up, power-down and when leaving the standby condition, the EN/FAULT pin is forced low until the

internal circuitry stabilize.

6.2

Microstepping sequencer

The value of the MODEx inputs is latched at power-up and when the device exits the STBY condition. After this,

the input value is unimportant and the MODE3 and MODE4 inputs start operating as step-clock and direction

input.

The only exception is the MODE1 = MODE2 = LOW condition; in this case the system is forced into full-step

mode. The previous condition is restored as soon as the MODE1 and MODE2 inputs switch to a different

combination.

An example of mode selection is shown in Figure 5. STCK and DIR timing.

At each STCK rising edge, the sequencer of the device is increased (DIR input high) or decreased (DIR input low)

of a module selected through the MODEx inputs as listed in Table 8. Step mode selection through MODEx inputs.

The sequencer is a 10-bit counter that sets the reference value of the PWM current controller and the direction of

the current for both of the H bridges.

MODE3

(STCK)

MODE4

(DIR)

MODE1

MODE2

Step mode

0

0

0

0

Full-step

0

0

0

1

0

0

1

0

0

0

1

1

0

1

0

0

0

1

0

1

0

1

1

0

0

1

1

1

1

0

0

0

(1)

1

0

0

1

1

0

1

0

1/2 step

1

0

1

1

1

1

0

0

(1)

1

1

0

1

STSPIN220

Functional description

DS11633 - Rev 4

page 9/27