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Figure 10: Two-Phase-on (Normal Mode) Drive

Figure 11: One-Phase-on (Wave Mode) Drive

RESET, ENABLE AND HOME SIGNALS

The RESET is an asynchronous reset input which

restores the module to the home position (state 1 :

ABCD = 0101). Reset is active when low.

The HOME output signals this condition and it is

intended to be ANDed with the output of a mechani-

cal home position sensor.

The ENABLE input is used to start up the module

after the system initialization. ENABLE is active

when high or unconnected.

MOTOR CURRENT REGULATION

The two bipolar winding currents are controlled by

two internal choppers in a PWM mode to obtain

good speed and torque characteristics.

An internal oscillator supplies pulses at the chopper

frequency to both choppers.

When the outputs are enabled, the current through

reached. At this moment the outputs are disabled

and the current decays until the next oscillator pulse

arrives.

The decay time of the current can be selected by

the CONTROL input (pin 10). If the CONTROL input

is kept high or open the decay is slow, as shown in

fig. 12, where the equivalent power stage of GS-

D200, the voltages on A and B are shown as well

as the current waveform on winding AB.

When the CONTROL input is forced low, the decay

is fast as shown in fig. 13.

The CONTROL input is provided on GS-D200 and

GS-D200S to allow maximum flexibility in applica-

tion.

If the modules must drive a large motor that does

not store much energy in the windings, the chopper

frequency must be decreased: this is easily ob-

tained by connecting an external capacitor between

OSC pin and GND1.

In these conditions a fast decay (CONTROL LOW)

would impose a low average current and the torque

could be inadequate. By selecting CONTROL

HIGH, the average current is increased thanks to

the slow decay.

When the GS-D200S is used in the fast-decay

mode it is recommended to connect external fast

recovery, low drop diodes between each phase

output and the supply return (GND). The slow-de-

cay should be the preferred operating recirculation

mode because of the lower power dissipation and

low noise operations.

GS-D200/GS-D200S