NJM3777 查看數據表（PDF） - Japan Radio Corporation

零件编号

产品描述 (功能)

生产厂家

NJM3777

DUAL STEPPER MOTOR DRIVER

Japan Radio Corporation  

NJM3777

s FUNCTIONAL DESCRIPTION

Each channel of the NJM3777 consists of the following sections: an output H-bridge with four transistors and four

recirculation diodes, capable of driving up to 800 mA 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.

Constant current control is achieved by switching the output current to the windings. This is done by sensing the

peak current through the winding via a current-sensing resistor RS, effectively connected in series with the motor

winding. As the current increases, a voltage develops across the sensing resistor, which is fed back to the com-

parator. At the predetermined level, defined by the voltage at the reference input VR, the comparator resets the flip-

flop, which turns off the upper output transistor. The turn-off of one channel is independent of the other channel.

The current decreases until the clock oscillator triggers the flip-flops of both channels simultaneously, which turns

on the output transistors again, and the cycle is repeated.

To prevent erroneous switching due to switching transients at turn-on, the NJM3777 includes a digital filter. The

clock oscillator provides a blanking pulse which is used for digital filtering of the voltage transient across the

current sensing resistor during turn-on.

The current paths during turn-on, turn-off and phase shift are shown in figure 3.

VMM

1

2

3

RS

Motor Current

1

2

3

Fast Current Decay

Slow Current Decay

Time

Figure 3. Output stage with current paths

during turn-on, turn-off and phase shift.

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