February 1999
PBL 3771/1
Precision Stepper Motor Driver
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.
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.
V
CC
V
–
+
CC
R
S
Q
M
A1
+
–
Logic
M
B1
P
PBL 3771/1
V
MM1
+
–
V
MM2
M
B2
–
+
+
–
Phase
2
CD
2
V
R2
C
2
GND
E
2
28-pin PLCC package
22-pin plastic DIP package
24-pin SO package
Figure 1. Block diagram.
1
PB
L
S
R
Q
37
RC
71
/1
Logic
M
A2
B
L
B 1
P 71/
37
L
37
Phase
1
CD
1
V
R1
C
1
E
1
71
/1
ERICSSON [ ERICSSON ]
