pbl3771so ETC-unknow, pbl3771so Datasheet - Page 6

• Manufacturer Part Number: pbl3771so
• Description: Precision Stepper Motor Driver
• Manufacturer: ETC-unknow

PBL 3771/1
External components
The voltage across the sensing resistor
is fed back to the comparator via a low-
pass filter section, to prevent erroneous
switching due to switching transients.
The recommended filter component
values, 1 kohm and 820 pF, are suitable
for a wide range of motors and
operational conditions.
introduces a small delay of the signal to
the comparator, peak voltage across the
sensing resistor, and hence the peak
motor current, will reach a slightly higher
level than the threshold, V
reference voltage
(V
may therefore be reduced to minimize
the delay and optimize low-current
performance, especially if a low (12 V)
supply voltage is used. Increasing the
time constant may result in unstable
switching.
set by the R-C combination at pin RC.
The recommended values give a
nominal frequency of 26.5 kHz. A lower
Figure 7. Microstepping system with PBM 3960 /1 and PBL 3771/1.
6
Since the low-pass filtering action
C
The time constant of the low-pass filter
The frequency of the clock oscillator is
= 450 mV @V
+2.5V
To
P
GND
(V
V
CC
CC
R
14
15
16
17
22
= 2.5 V).
)
7
6
1
(+5 V)
D0
D7
A0
A1
WR
CS
RESET
V
Ref
C
, set by the
PBM 3960/1
V
V DD
SS
5
18
frequency will result in higher current
ripple and may cause audible noise from
the motor, while increasing the
frequency results in higher switching
losses and possibly increased iron
losses in the motor.
selected for maximum motor current.
The relationship between peak motor
current, reference voltage and the value
of R
control” above. Be sure not to exceed
the maximum output current which is
650 mA per channel (or 500 mA per
channel, both channels fully on, see
“Recommended Operating Conditions”).
Motor selection
The PBL 3771/1 is designed for bipolar
motors, i.e., motors that have only one
winding per phase. A unipolar motor,
having windings with a center tap, can
also be used, see figure 14.
PBL 3771/1 is based on a constant
frequency and a varying duty cycle. This
scheme imposes certain restrictions on
motor selection. Unstable chopping can
The sensing resistor, R
The chopping principle in the
Sign
Sign
CD
CD
DA
DA
S
is described under “Current
1
1
1
2
2
2
19
3
20
4
2
21
+5 V
15 k
3 300 pF
16
15
14
7
8
9
12
Phase
CD
V
Phase
CD
V
RC
R1
R2
0.1 F
1
2
S
, should be
5,
17, 18
GND
1
2
V
6,
CC
11
PBL 3771/1
C
1
10
820 pF
1 k
1.0
V
MM1
3
2
E
1
occur if the chopping duty cycle exceeds
approximately 50%. To avoid this, it is
necessary to choose a motor with a low
winding resistance. Low winding
resistance means less inductance and
will therefore enable higher stepping
rates, however it also means less torque
capability. A compromise has to be
made.
possible winding resistance that still
gives the required torque and use as
high supply voltage as possible without
exceeding the maximum recommended
40 V. Check that the chopping duty cycle
does not exceed 50% at maximum
current.
regulated, constant output current it is
not necessary to use a motor that is
rated at the same voltage as the actual
supply voltage. Only rated current needs
to be considered. Typical motors to be
used together with the PBL 3771/1 have
voltage ratings of 5 to 12 V, while the
supply voltage usually ranges from 24 to
40 V.
R S
13
Choose a motor with the lowest
Since the PBL 3771/1 produces a
C
V
2
820 pF
MM2
20
1 k
1.0
M
M
M
M
21
E
A1
B1
A2
B2
2
0.1 F
R S
4
1
19
22
Pin numbers refer
to DIL package.
GND (V
+
10 F
STEPPER
MOTOR
V
MM
MM
)