NJM3774 New Japan Radio, NJM3774 Datasheet - Page 3

• Manufacturer Part Number: NJM3774
• Description: DUAL STEPPER MOTOR DRIVER
• Manufacturer: New Japan Radio

Each channel of the NJM3774 consists of the following sections: an output H-bridge with four transistors, capable
of driving up to 1000mA continuous current to the motor winding; a logic section that controls the output transistors;
an S-R flip-flop; and a comparator. The clock-oscillator is common to both channels.
peak current through the winding via a resistor, R
turn-on period. As the current increases, a voltage develops across the resistor, and is fed back to the comparator.
At the predetermined level defined by the voltage at the reference input V
turning off the output transistors. The current decreases until the clock oscillator triggers the flip-flop, turning on the
output transistors, and the cycle is repeated.
diodes are connected to the circuit externally.
Constant current control is achieved by switching the output current to the windings. This is done by sensing the
The current paths during turn-on, turn-off and phase shift are shown in figure 3. Note that the upper recirculation
FUNCTIONAL DESCRIPTION
Figure 3. Output stage with current paths
during turn-on, turn-off and phase shift.
Motor Current
3
External recirculation diodes
Fast Current Decay
Slow Current Decay
1
1
S
, effectively connected in series with the motor winding during the
V
R
2
MM
S
2
3
R
, the comparator resets the flip-flop,
Time
NJM3774