A3964
Dual Full-Bridge PWM Motor Driver
Features and Benefits
▪
±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
Description
Designed for pulse width modulated (PWM) current control
of bipolar stepper motors, the A3964 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 transitions. 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
Continued on the next page…
Package: 20 pin SOIC (suffix LB)
Not to scale
Functional Block Diagram
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
SOURCE
DISABLE
V
REF(IN)
–
+
ONE SHOT
ONE SHOT
REF OUT
RC1
RT
CT
RA
RS
RB
RS
RC2
RT
Dwg. FP-033-1
5 6 15 16
SENSE 2
8
SENSE 1
2
14
REF IN
7
19
13
CT
29319.28g
A3964
Description (continued)
Dual Full-Bridge PWM Motor Driver
The A3964 is supplied in a 20-lead SOIC with internally fused pins
for enhanced thermal dissipation. The package is lead (Pb) free with
100% matte tin leadframe plating. The power pins are at ground
potential and need no electrical isolation.
each bridge the ENABLE input, when held high, disables the output
drivers. Special power-up sequencing is not required. Internal circuit
protection includes thermal shutdown with hysteresis, transient-
suppression diodes, and crossover-current protection.
Selection Guide
Part Number
A3964SLB-T
A3964SLBTR-T
Packing
20-pin SOIC with internally fused pins
20-pin SOIC with internally fused pins
Package
37 per tube
1000 per reel
Absolute Maximum Ratings
Characteristic
Load Supply Voltage
Logic Supply Voltage
Input Voltage
Sense Voltage
Reference Output Current
Output Current
Package Power Dissipation
Operating Ambient Temperature
Maximum Junction Temperature
Storage Temperature
Symbol
V
BB
V
CC
V
IN
V
S
I
REF(OUT)
I
OUT
P
D
T
A
T
J
(max)
T
stg
ALLOWABLE PACKAGE POWER DISSIPATION (W)
Notes
Rating
33
7.0
–0.3 to V
DD
+ 0.3
1.0
1.0
Units
V
V
V
V
mA
A
mA
–
ºC
ºC
ºC
Output current rating may be limited by duty cycle, am-
bient temperature, and heat sinking. Under any set of
conditions, do not exceed the specified current rating
or a junction temperature of 150°C.
See graph
Range S
t
w
= 10
μs
Continuous
±1.0
±800
–
–20 to 85
150
–55 to 150
Fault conditions that produce excessive junction temperature will activate
the device’s thermal shutdown circuitry. These conditions can be toler-
ated but should be avoided.
Pin-out Diagram
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
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
5
R
JT
= 6.0 C/W
4
3
2
PWM 2
9
8
13
φ
2
12
11
1
SUFFIX 'LB', R
JA
= 61 C/W
9
10
φ
1
PWM 1
0
25
50
75
100
TEMPERATURE IN C
125
150
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
A3964
Dual Full-Bridge PWM Motor Driver
ELECTRICAL CHARACTERISTICS (continued) at T
A
= +25°C, V
BB
= 30 V, V
CC
= 4.75 V to 5.25 V,
V
SENSE
= 0 V, 30 kΩ and 1000 pF RC to Ground (unless noted otherwise)
Limits
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Control Logic
Logic Supply Voltage Range
Logic Input Voltage
Logic Input Current
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
CC
V
IN(1)
V
IN(0)
I
IN(1)
I
IN(0)
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
Thermal Shutdown Temp.
Thermal Shutdown Hysteresis
UVLO Disable Threshold
UVLO Hysteresis
UVLO Enable Threshold
Logic Supply Current
Logic Supply Current
Temperature Coefficient
I
CC(ON)
I
CC(OFF)
∆I
CC(ON)
T
J
∆T
J
Decreasing V
CC
UVLO Enable Volt. - UVLO Disable Volt.
Increasing V
CC
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
—
—
—
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
—
—
—
—
—
—
—
—
—
—
4.65
0.175
4.725
85
17
—
μs
μs
μs
μs
μs
μs
μs
μs
°C
°C
V
V
V
mA
mA
mA/°C
Operating
4.75
2.4
—
—
—
2.45
150
-2.5
-6.0
-0.3
27
—
—
—
—
—
<1.0
<-2.0
2.50
—
0
0
—
30
1.2
2.5
5.25
—
0.8
20
-200
2.55
900
1.0
6.0
1.0
33
2.0
3.6
V
V
V
μA
μA
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.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
A3964
Dual Full-Bridge PWM Motor Driver
FUNCTIONAL DESCRIPTION
Internal PWM Current Control.
The A3964 contain a
fi
xed
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
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:
V
REF(IN)
I
TRIP
≈
R
S
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 comparator resets a latch
that turns off the selected source driver. The load inductance
causes the current to recirculate through the sink driver and
fl
yback 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 the RC Fixed
Off-time section, 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 the Load Current Regulation section, 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
fi
xed off-time of
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:
[(V
BB
– V
SAT(SOURCE+SINK)
) x t
ON(min)
max] – [1.05 (V
SAT(SINK)
+ V
F
) x t
OFF
]
I
AVG
≈
1.05 (t
ON(min)
max + t
OFF
) x R
LOAD
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 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
where t
OFF
= R
T
C
T
, R
LOAD
is the series resistance of the load,
V
BB
is the motor supply voltage and t
ON(min)
max is specified in
the electrical characteristics table. When the motor is rotating,
the back EMF generated will influence the above relationship.
For brush dc motor applications, the current regulation is
improved. For stepper motor applications when the motor is
rotating, the effect is dependent on the polarity and magnitude of
the motor’s back EMF.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
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