3962
DUAL FULL-BRIDGE
PWM MOTOR DRIVER
3962
Designed for pulse-width modulated (PWM) current control of
bipolar stepper motors, the A3962SLB is 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 A3962SLB is supplied in a 20-lead plastic SOIC with copper
heat sink tabs. The power tab is at ground potential and needs no
electrical isolation.
Data Sheet
29319.27
DUAL FULL-BRIDGE PWM MOTOR DRIVER
SENSE
1
OUT
1A
LOAD
SUPPLY
GROUND
GROUND
V
REF(IN)
PHASE
1
ENABLE
1
ABSOLUTE MAXIMUM RATINGS
Load Supply Voltage, V
BB
. . . . . . . . .
30 V
Output Current, I
OUT
. . . . . . . . . .
±
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
SENSE
. . . . . . . . . . . .
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 tempera
ture of 150˚C.
T
C
U
D LY
O N
R O
P
D CE
B
E N
SL
U E
4
IN R
96
T E
3
N F
A
O E
e
C R
e
IS R
S
D O
—
F
2
3
4
5
1
2
19
18
SENSE
2
OUT
2A
V
BB
V
CC
17
LOGIC
SUPPLY
16
GROUND
6
15
GROUND
7
14
13
12
11
V
REF(OUT)
RC
2
RC
1
9
8
9
PWM 1
PWM 2
OUT
1B
1
20
OUT
2B
θ
1
θ
2
PHASE
2
10
ENABLE
2
Dwg. PP-047-1
FEATURES
s
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
Automotive Capable
† Fault conditions that produce excessive junction
temperature will activate the device’s thermal
shutdown circuitry. These conditions can be
tolerated but should be avoided.
Always order by complete part number:
A3962SLB
.
3962
DUAL FULL-BRIDGE
PWM MOTOR DRIVER
ALLOWABLE PACKAGE POWER DISSIPATION in WATTS
2.5
TRUTH TABLE
R
θJT
= 6°C/W
2.0
ENABLE
H
L
PHASE
X
H
L
OUT
A
Off
H
L
OUT
B
Off
L
H
1.5
1.0
R
θJA
= 60°C/W
L
0.5
X = Irrelevant
0
25
50
75
100
125
150
TEMPERATURE in
°C
Dwg. GP-019-1
FUNCTIONAL BLOCK DIAGRAM AND TYPICAL
BIPOLAR STEPPER MOTOR APPLICATION
MOTOR SUPPLY
C
BB
V
BB
V
CC
C
CC
LOGIC SUPPLY
OUT
1A
OUT
1B
OUT
2A
OUT
2B
ENABLE 1
PHASE 1
CONTROL LOGIC
AND LEVEL SHIFT
BLANKING
TIME AND
SOURCE
DRIVER T
OFF
CONTROL
UVLO
AND
TSD
VOLTAGE
REFERENCE
CONTROL LOGIC
AND LEVEL SHIFT
BLANKING
TIME AND
SOURCE
DRIVER T
OFF
CONTROL
ENABLE 2
PHASE 2
+
_
+
_
RC1
SENSE 1
GND
REF
OUT
R
1
REF
IN
SENSE
2
RC
2
R
T1
C
T1
R
S1
R
2
R
S2
C
T2
R
T2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 1995 Allegro MicroSystems, Inc.
3962
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)
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
OUT
= V
BB
V
OUT
= 0 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
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
<1.0
<1.0
1.0
1.1
—
0.3
0.5
—
1.1
1.3
—
5.0
5.0
30
30 +V
F
50
-50
1.2
1.5
1.7
0.6
1.2
1.5
1.4
1.6
1.7
7.0
7.0
V
V
µA
µA
V
V
V
V
V
V
V
V
V
mA
mA
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)
V
IN
= 2.4 V
V
IN
= 0.8 V
Operating
4.75
2.4
—
—
—
—
—
—
<1.0
<-2.0
5.25
—
0.8
20
-200
V
V
V
µA
µA
Continued next page…
3962
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 (Continued)
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
CC
= 5.0 V, I
REF OUT
= 90 to 900
µA
3 kΩ
≤
R
D
= R
1
+ R
2
≤
15 kΩ
V
REF IN
= 1 V
V
REF
= 0 V
Operating
C
T
= 1000 pF, R
T
= 30 kΩ
Comparator Trip to Source OFF
C
T
= 1000 pF
±
5%, 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
Thermal Shutdown Temp.
Thermal Shutdown Hysteresis
UVLO Disable Threshold
UVLO Hysteresis
Logic Supply Current
I
CC(ON)
I
CC(OFF)
Logic Supply Current
Temperature Coefficient
∆I
CC(ON)
V
ENABLE1
= V
ENABLE2
= 0.8 V
V
ENABLE1
= V
ENABLE2
= 2.4 V
V
ENABLE 1
= V
ENABLE 2
= 0.8 V
T
J
∆T
J
—
—
—
—
—
—
—
—
—
—
2.5
0.7
—
—
—
3.2
1.2
3.2
0.7
3.2
3.2
0.7
1.2
165
15
2.7
0.9
60
11
0.18
—
—
—
—
—
—
—
—
—
—
2.9
1.1
85
17
—
µs
µs
µs
µs
µs
µs
µs
µs
°C
°C
V
V
mA
mA
mA/°C
2.45
150
-2.5
-6.0
-0.3
27
—
—
2.50
—
0
0
—
30
1.2
2.5
2.55
900
1.0
6.0
1.0
33
2.0
3.6
V
µA
µA
mV
V
µs
µs
µs
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
3962
DUAL FULL-BRIDGE
PWM MOTOR DRIVER
FUNCTIONAL DESCRIPTION
Internal PWM Current Control.
The A3962SLB contains
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
internal current-control circuitry (or by the PHASE or
ENABLE inputs). The comparator output is blanked to
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 3.0 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 3.0 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
3.0 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 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 (R
D
= R
1
+R
2
)
should have an impedance of 3 kΩ to 15 kΩ. 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
comparator resets a latch that turns off the selected source
driver. The load inductance causes the current to recircu-
late 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
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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