February 1999

Description

The PBL 3771/1 is a switch-mode, constant-current driver IC (chopper) with two

channels, one for each winding of a two-phase stepper motor. The circuit is especially

developed for use in microstepping applications in conjunction with the matching dual

DAC (Digital-to-Analog Converter) PBM 3960. A complete driver system consists of

these two ICs, a few passive components and a microprocessor for generation of the

proper control and data codes required for microstepping.

The PBL 3771/1 contains a clock oscillator, which is common for both driver

channels; a set of comparators and flip-flops implementing the switching control; and

two H-bridges with internal recirculation diodes. Voltage supply requirements are +5 V

for logic and +10 to +45 V for the motor. Maximum output current is 650 mA per

channel.

A special logic function is used to select slow or fast current decay in the output

stage for improved high-speed microstepping.

The close match between the two driver channels guarantees consistent output

current ratios and motor positioning accuracy.

PBL 3771/1

Precision Stepper Motor Driver

Figure 1. Block diagram.

28-pin PLCC package

22-pin plastic DIP package

24-pin SO package

Key Features

•

Dual chopper driver in a single

package.

•

650 mA output current per channel.

•

Close matching between channels for

high microstepping accuracy.

•

Selectable slow/fast current decay for

improved high-speed microstepping.

•

Improved low-level linearity.

•

Specially matched to Dual DAC

PBM 3960.

•

Selection of packages, 22-pin

“batwing” DIP, 24 pin "batwing" SOIC

or 28-lead PLCC with lead-frame for

heat-sinking through PC board

copper.

RC

PBL 3771/1

M

B2

M

A2

GND

V

R2

CD

2

V

CC

V

CC

S

R

Q

+

–

+

–

Logic

S

R

Q

+

–

+

–

Logic

+

–

1