3964
DUAL FULL-BRIDGE
PWM MOTOR DRIVER
3964
Designed for pulse-width modulated (PWM) current control of
bipolar stepper motors, the A3964SB and A3964SLB are capable of
continuous output currents to
±800
mA and operating voltages to 30 V.
Internal fixed off-time PWM current-control circuitry can be used to
regulate the maximum load current to a desired value. An internal
precision voltage reference is provided to improve motor peak-current
control accuracy. The peak load current limit is set by the user’s
selection of an external resistor divider and current-sensing resistors.
The fixed off-time pulse duration is set by user-selected external
RC timing networks. The capacitor in the RC timing network also
determines a user-selectable blanking window that prevents false
triggering of the PWM current control circuitry during switching transi-
tions. This eliminates the need for two external RC filter networks on
the current-sensing comparator inputs.
For each bridge the PHASE input controls load current polarity by
selecting the appropriate source and sink driver pair. For each bridge
the ENABLE input, when held high, disables the output drivers. Spe-
cial power-up sequencing is not required. Internal circuit protection
includes thermal shutdown with hysteresis, transient-suppression
diodes, and crossover-current protection.
The A3964SB is supplied in a 24-pin plastic DIP with copper heat
sink tabs; A3964SLB is supplied in a 20-lead plastic SOIC with copper
heat sink tabs. The power tabs are at ground potential and need no
electrical isolation.
Data Sheet
29319.28*
DUAL FULL-BRIDGE PWM MOTOR DRIVER
A3964SLB
OUT
1B
SENSE
1
OUT
1A
LOAD
SUPPLY
GROUND
GROUND
V
REF(IN)
RC
1
PHASE
1
ENABLE
1
1
2
3
4
5
6
7
9
8
V
BB
V
CC
1
2
20
19
18
17
16
15
14
OUT
2B
SENSE
2
OUT
2A
LOGIC
SUPPLY
GROUND
GROUND
V
REF(OUT)
RC
2
PHASE
2
ENABLE
2
PWM 2
13
θ
2
12
11
9
10
θ
1
PWM 1
Dwg. PP-047-1
ABSOLUTE MAXIMUM RATINGS
Load Supply Voltage, V
BB
. . . . . . . . .
33 V
Output Current, I
OUT
(10
µs)
. . . . . .
±
1.0 A*
(continuous) . . . . . . . . . . . . .
±
800 mA*
Logic Supply Voltage, V
CC
. . . . . . . . .
7.0 V
Logic Input Voltage Range,
V
IN
. . . . . . . . . . .
-0.3 V to V
CC
+ 0.3 V
Sense Voltage, V
S
. . . . . . . . . . . . . . .
1.0 V
Reference Output Current,
I
REF(OUT)
. . . . . . . . . . . . . . . . . .
1.0 mA
Package Power Dissipation,
P
D
. . . . . . . . . . . . . . . . . . . .
See Graph
Operating Temperature Range,
T
A
. . . . . . . . . . . . . . . .
-20˚C to +85˚C
Junction Temperature, T
J
. . . . . . .
+150˚C†
Storage Temperature Range,
T
S
. . . . . . . . . . . . . . .
-55˚C to +150˚C
* Output current rating may be limited by duty cycle,
ambient temperature, and heat sinking. Under any set
of conditions, do not exceed the specified current rating
or a junction temperature of 150˚C.
† Fault conditions that produce excessive junction
temperature will activate the device’s thermal shutdown
circuitry. These conditions can be tolerated but should
be avoided.
FEATURES
s
s
s
s
s
s
s
±800
mA Continuous Output Current Rating
30 V Output Voltage Rating
Internal PWM Current Control, Saturated Sink Drivers
Internally Generated, Precision 2.5 V Reference
Internal Transient-Suppression Diodes
Internal Thermal-Shutdown Circuitry
Crossover-Current Protection, UVLO Protection
Always order by complete part number:
Part Number
A3964SB
A3964SLB
Package
24-Pin DIP
20-Lead Wide-Body SOIC
3964
DUAL FULL-BRIDGE
PWM MOTOR DRIVER
A3964SB
ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS
5
R
θJT
= 6.0°C/W
NO
CONNECT.
OUT
1B
SENSE
1
1
2
3
4
5
6
7
8
9
9
NC
NC
24
23
NO
CONNECT.
OUT
2B
SENSE
2
OUT
2A
LOGIC
SUPPLY
GROUND
GROUND
V
REF(OUT)
RC
2
PHASE
2
ENABLE
2
NO
CONNECT.
4
1
2
22
21
3
SUFFIX 'B', R
θJA
= 40°C/W
OUT
1A
LOAD
SUPPLY
GROUND
GROUND
V
BB
V
CC
20
19
18
17
2
1
SUFFIX 'LB', R
θJA
= 60°C/W
V
REF(IN)
RC
1
PWM 2
16
θ
2
15
14
0
25
50
75
100
TEMPERATURE IN
°C
125
150
Dwg. GP-049-4
PHASE
1
ENABLE
1
NO
CONNECT.
10
11
12
θ
1
PWM 1
NC
NC
13
Dwg. PP-005-2
FUNCTIONAL BLOCK DIAGRAM
(A3964SLB pinning shown)
LOGIC
SUPPLY
OUT 1B
LOAD
SUPPLY
OUT 2A
OUT 1A
OUT 2B
17
V
CC
3
1
4
18
20
UVLO
& TSD
V
BB
PWM 1
1
2
ENABLE1
10
PWM 2
PHASE 1
9
12
PHASE 2
11
ENABLE2
SOURCE
DISABLE
–
+
2.5 V
REFERENCE
V
REF(IN)
–
+
SOURCE
DISABLE
ONE SHOT
ONE SHOT
REF OUT
SENSE 1
SENSE 2
RC1
RT
CT
RA
RS
RB
RS
RC2
8
2
14
REF IN
7
5 6 15 16
19
13
CT
RT
Dwg. FP-033-1
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 1997 Allegro MicroSystems, Inc.
3964
DUAL FULL-BRIDGE
PWM MOTOR DRIVER
TRUTH TABLE
ENABLE
H
L
L
PHASE
X
H
L
OUT
A
Off
H
L
OUT
B
Off
L
H
X = Irrelevant
ELECTRICAL CHARACTERISTICS at T
A
= +25
°
C, V
BB
= 30 V, V
CC
= 4.75 V to 5.25 V,
V
S
= 0 V, 30 k
Ω
& 1000 pF RC to Ground (unless noted otherwise)
Limits
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Output Drivers
Load Supply Voltage Range
Output Sustaining Voltage
Output Leakage Current
V
BB
V
CE(sus)
I
CEX
Operating, I
OUT
=
±800
mA, L = 3 mH
I
OUT
=
±800
mA, L = 3 mH, V
BB
= 33 V
V
OUT
= V
BB
= 33 V
V
OUT
= 0 V, V
BB
= 33 V
Output Saturation Voltage
V
CE(SAT)
Source Driver, I
OUT
= -500 mA
Source Driver, I
OUT
= -750 mA
Source Driver, I
OUT
= -800 mA
Sink Driver, I
OUT
= +500 mA
Sink Driver, I
OUT
= +750 mA
Sink Driver, I
OUT
= +800 mA
Clamp Diode Forward Voltage
(Sink or Source)
V
F
I
F
= 500 mA
I
F
= 750 mA
I
F
= 800 mA
Motor Supply Current
(No Load)
I
BB(ON)
I
BB(OFF)
V
ENABLE
= 0.8 V
V
ENABLE
= 2.4 V
5.0
33
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
<1.0
<1.0
1.0
1.1
—
0.3
0.5
—
1.1
1.3
—
2.0
0
30
—
50
-50
1.2
1.5
1.7
0.6
1.2
1.5
1.4
1.6
1.7
4.0
500
V
V
µA
µA
V
V
V
V
V
V
V
V
V
mA
µA
NOTES: 1. Typical Data is for design information only.
2. Negative current is defined as coming out of (sourcing) the specified device terminal.
3964
DUAL FULL-BRIDGE
PWM MOTOR DRIVER
ELECTRICAL CHARACTERISTICS at T
A
= +25
°
C, V
BB
= 30 V, V
CC
= 4.75 V to 5.25 V, V
SENSE
= 0
V, 30 k
Ω
& 1000 pF RC to Ground (unless noted otherwise) (cont.)
Limits
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Control Logic
Logic Supply Voltage Range
Logic Input Voltage
V
CC
V
IN(1)
V
IN(0)
Logic Input Current
I
IN(1)
I
IN(0)
Reference Output Voltage
Reference Output Current
Ref. Input Offset Current
Comparator Input Offset Volt.
Comparator Input Volt. Range
PWM RC Fixed Off-time
PWM Propagation Delay Time
PWM Minimum On Time
Propagation Delay Times
V
REF(OUT)
I
REF(OUT)
I
OS
V
IO
V
REF
t
OFF RC
t
PWM
t
ON(min)
t
pd
V
IN
= 2.4 V
V
IN
= 0.8 V
V
CC
= 5.0 V, I
REF(OUT)
= 90 to 900
µA
3 kΩ
≤
R
D
= R
A
+ R
B
≤
15 kΩ
V
REF(IN)
= 1 V
V
REF(IN)
= 0 V
Operating
C
T
= 1000 pF, R
T
= 30 kΩ
Comparator Trip to Source OFF
C
T
= 1000 pF, R
T
≥
15 kΩ, V
CC
= 5 V
I
OUT
=
±800
mA, 50% to 90%:
ENABLE ON to Source ON
ENABLE OFF to Source OFF
ENABLE ON to Sink ON
ENABLE OFF to Sink OFF
PHASE Change to Sink ON
PHASE Change to Source ON
PHASE Change to Sink OFF
PHASE Change to Source OFF
Operating
4.75
2.4
—
—
—
2.45
150
-2.5
-6.0
-0.3
27
—
—
—
—
—
—
—
—
—
—
—
—
Decreasing V
CC
UVLO Enable Volt. - UVLO Disable Volt.
Increasing V
CC
I
CC(ON)
I
CC(OFF)
Logic Supply Current
Temperature Coefficient
∆I
CC(ON)
V
ENABLE 1
= V
ENABLE 2
= 0.8 V
V
ENABLE 1
= V
ENABLE 2
= 2.4 V
V
ENABLE 1
= V
ENABLE 2
= 0.8 V
4.20
0.075
4.375
—
—
—
—
—
—
<1.0
<-2.0
2.50
—
0
0
—
30
1.2
2.5
3.2
1.2
3.2
0.7
3.2
3.2
0.7
1.2
165
15
4.40
0.125
4.525
60
13
0.18
5.25
—
0.8
20
-200
2.55
900
1.0
6.0
1.0
33
2.0
3.6
—
—
—
—
—
—
—
—
—
—
4.65
0.175
4.725
85
17
—
V
V
V
µA
µA
V
µA
µA
mV
V
µs
µs
µs
µs
µs
µs
µs
µs
µs
µs
µs
°C
°C
V
V
V
mA
mA
mA/°C
Thermal Shutdown Temp.
Thermal Shutdown Hysteresis
UVLO Disable Threshold
UVLO Hysteresis
UVLO Enable Threshold
Logic Supply Current
T
J
∆T
J
NOTES: 1. Typical Data is for design information only.
2. Negative current is defined as coming out of (sourcing) the specified device terminal.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
3964
DUAL FULL-BRIDGE
PWM MOTOR DRIVER
FUNCTIONAL DESCRIPTION
Internal PWM Current Control.
The A3964SB and
A3964SLB contain a fixed off-time pulse-width modulated
(PWM) current-control circuit that can be used to limit the
load current to a desired value. The peak value of the
current limiting (I
TRIP
) is set by the selection of an external
current-sensing resistor (R
S
) and reference input voltage
(V
REF(IN)
). The internal circuitry compares the voltage
across the external sense resistor to the voltage on the
reference input terminal (V
REF(IN)
) resulting in a
transconductance function approximated by:
I
TRIP
≈
V
REF(IN)
R
S
prevent false over-current detections due to reverse-
recovery currents of the clamp diodes, and/or switching
transients related to distributed capacitance in the load.
During internal PWM operation, at the end of the t
OFF
time, the comparator’s output is blanked and C
T
begins to
be charged from approximately 1.1 volts by an internal
current source of approximately 1 mA. The comparator
output remains blanked until the voltage on C
T
reaches
approximately 3 volts.
When a transition of the PHASE input occurs, C
T
is discharged to near ground during the crossover delay
time (the crossover delay time is present to prevent
simultaneous conduction of the source and sink drivers).
After the crossover delay, C
T
is charged by an internal
current source of approximately 1 mA. The comparator
output remains blanked until the voltage on C
T
reaches
approximately 3 volts.
When the device is disabled, via the ENABLE input,
C
T
is discharged to near ground. When the device is
re-enabled, C
T
is charged by an internal current source of
approximately 1 mA. The comparator output remains
blanked until the voltage on C
T
reaches approximately
3 volts.
The minimum recommended value for C
T
is
1000 pF.
This value ensures that the blanking time is
sufficient to avoid false trips of the comparator under
normal operating conditions. For optimal regulation of the
load current, the above value for C
T
is recommended and
the value of R
T
can be sized to determine t
OFF
. For more
information regarding load current regulation, see below.
Load Current Regulation.
Because the device operates
in a slow current-decay mode (2-quadrant PWM mode),
there is a limit to the lowest level that the PWM current
control circuitry can regulate load current. The limitation is
due to the minimum PWM duty cycle, which is a function of
the user-selected value of t
OFF
and the minimum on-time
pulse t
ON(min)
max that occurs each time the PWM latch is
reset. If the motor is not rotating, as in the case of a
stepper motor in hold/detent mode, a brush dc motor when
stalled or at startup, the worst case value of current
regulation can be approximated by:
The reference input voltage is typically set with a
resistor divider from V
REF(OUT)
. To ensure proper operation
of the voltage reference, the resistor divider should have
an impedance of 3 kΩ to 15 kΩ (R
D
= R
A
+R
B
). Within this
range, a low impedance will minimize the effect of the REF
IN input offset current.
The current-control circuitry limits the load current as
follows: when the load current reaches I
TRIP
, the compara-
tor resets a latch that turns off the selected source driver.
The load inductance causes the current to recirculate
through the sink driver and flyback diode.
For each bridge, the user selects an external resistor
(R
T
) and capacitor (C
T
) to determine the time period
(t
OFF
= R
T
C
T
) during which the source driver remains
disabled (see “RC Fixed Off-time” below). The range of
recommended values for C
T
and R
T
are 1000 pF to 1500
pF and 15 kΩ to 100 kΩ respectively. For optimal load
current regulation, C
T
is normally set to 1000 pF (see
“Load Current Regulation” below). At the end of the RC
interval, the source driver is enabled allowing the load
current to increase again. The PWM cycle repeats,
maintaining the peak load current at the desired value.
RC Blanking.
In addition to determining the fixed off-time
of the PWM control circuit, the C
T
component sets the
comparator blanking time. This function blanks the output
of the comparator when the outputs are switched by the
internal current-control circuitry (or by the PHASE or
ENABLE inputs). The comparator output is blanked to
I
AVG
≈
[(V
BB
– V
SAT(SOURCE+SINK)
) • t
ON(min)
max] – (1.05 (V
SAT(SINK)
+ V
F
) • t
OFF
)
1.05 (t
ON(min)
max + t
OFF
) • R
LOAD
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