JRC NJM3775E3, NJM3775D2, NJM3775FM2 Datasheet

DUAL STEPPER MOTOR DRIVER

■ GENERAL DESCRIPTION ■ PACKAGE OUTLINE

The NJM3775 is a switch-mode (chopper), constantcurrent driver with two channels: one for each winding of a two-phase stepper motor. NJM3775 is equipped with a Disable input to simplify half-stepping operation. The NJM3775 contains a clock oscillator, which is common for both driver channels, a set of comparators and flip-flops implementing the switching control, and two output H-bridges, including recirculation diodes. Voltage supply requirements are + 5 V for logic and + 10 to + 45 V for the motor. Maximum output current is 750mA per channel.

■ FEATURES

• Dual chopper driver

NJM3775D2

NJM3775FM2

NJM3775E3

NJM3775

• 750 mA continuous output current per channel

• Digital filter on chip eliminates external filtering components

• Packages DIP22 / PLCC28 / EMP24(batwing)

■ BLOCK DIAGRAM

C

Phase

1

NJM3775

V

CC

RC

V

CC

+ —

V

Dis

R1

1

— +

+ —

R S

SRQ

E

1

Q

M

A1

Logic

M

B1

V

MM1

V

MM2

M

B2

M

A2

Figure 1. Block diagram

Phase

Dis

V

2

R2

GNDC

2

E

2

■ PIN CONFIGURATIONS

NC

1 2

MB

1

E

3

1

4

MA

1

5

VMM

GND GND

VR

Phase

Dis

RC

1

C

1 1

1

6 7

8

9 10 11

NJM

3775E3

Figure 2. Pin configurations

24 23

22 21 20

19 18

17 16 15 14 1312

NC

MB E

2

MA VMM GND

GND VR C

2

Phase Dis V

cc

NJM3775

M

1

B1

E

2

M

V

MM1

GND GND

V

Phase

Dis

RC

1

A1

R1

C

1 1

1

3 4 5 6

3775D2

7 8

9 10 11

NJM

22 21 20 19 18 17 16 15 14 13 12

M

B2

E

2

M

A2

V

MM2

GND GND V

R2

C

2

Phase Dis

2

V

CC

MM2

GND

V

432

5

M

A2

E

6

2

7

M

B2

8

M

B1

NJM3775FM2

GND

9

E

10

1

11

M

A1

2

12131415161718

MM1

GND

V

GND

1

GND

R2

V

GND

282726

GND

C

25

Phase

2

24

Dis

2

23

V

CC

22

RC

21

Dis

1

20

Phase

1

19

C

1

R1

V

2

■ PIN DESCRIPTION

EMP DIP PLCC Symbol Description

2 1 [8] M 32[10]E 43[11]M 54[12]V

B1

1

A1

MM1

6,7 5, 6, [1-3, 9, GND Ground and negative supply. Note: these pins are used thermally for heat-sinking. 18,19 17, 18 13-17, Make sure that all ground pins are soldered onto a suitably large copper ground plane

28] for efficient heat sinking.

87[18]V

98[19]C

R1

1

10 9 [20] Phase

11 10 [21] Dis

12 11 [22] RC Clock oscillator RC pin. Connect a 12 kohm resistor to V

13 12 [23] V

CC

14 13 [24] Dis

15 14 [25] Phase

16 15 [26] C

17 16 [27] V

20 19 [4] V 21 20 [5] M 22 21 [6] E 23 22 [7] M

2

R2

MM2

A2

2

B2

Motor output B, channel 1. Motor current flows from MA1 to MB1 when Phase1 is HIGH. Common emitter, channel 1. This pin connects to a sensing resistor RS to ground. Motor output A, channel 1. Motor current flows from MA1 to MB1 when Phase1 is HIGH. Motor supply voltage, channel 1, +10 to +40 V. V

MM1

and V

should be connected together.

MM2

Reference voltage, channel 1. Controls the comparator threshold voltage and hence the output current. Comparator input channel 1. This input senses the instantaneous voltage across the sensing resistor, filtered by the internal digital filter or an optional external RC network. Controls the direction of motor current at outputs MA1 and MB1. Motor current flows from MA1 to

1

M

when Phase1 is HIGH.

B1

Disable input for channel 1. When HIGH, all four output transistors are turned off, which results

1

in a rapidly decreasing output current to zero.

and a 4 700 pF capacitor to ground

CC

to obtain the nominal switching frequency of 23.0 kHz and a digital filter blanking time of 1.0µs. Logic voltage supply, nominally +5 V. Disable input for channel 2. When HIGH, all four output transistors are turned off, which results

2

in a rapidly decreasing output current to zero. Controls the direction of motor current at outputs MA2 and MB2. Motor current flows from MA2 to

2

M

when Phase2 is HIGH.

B2

Comparator input channel 2. This input senses the instantaneous voltage across the sensing resistor, filtered by the internal digital filter or an optional external RC network. Reference voltage, channel 2. Controls the comparator threshold voltage and hence the output current. Motor supply voltage, channel 2, +10 to +40 V. V

MM1

and V

should be connected together.

MM2

Motor output A, channel 2. Motor current flows from MA2 to MB2 when Phase2 is HIGH. Common emitter, channel 2. This pin connects to a sensing resistor RS to ground. Motor output B, channel 2. Motor current flows from MA2 to MB2 when Phase2 is HIGH.

NJM3775

■ FUNCTIONAL DESCRIPTION

Each channel of the NJM3775 consists of the following sections: an output H-bridge with four transistors and four recirculation diodes, capable of driving up to 750 mA continuous current to the motor winding, a logic section that controls the output transistors, an S-R flip-flop, and a com- parator. 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 comparator. At the predetermined level, defined by the voltage at the reference input VR, the comparator resets the flipflop, 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 NJM3775 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.

V

1

MM

2

3

R

S

Motor Current

1 2

Fast Current Decay Slow Current Decay

3

Figure 3. Output stage with current paths during turn-on, turn-off and phase shift.

Time