3952
FULL-BRIDGE PWM MOTOR DRIVER
A3952SB
BRAKE
REF
RC
GROUND
GROUND
LOGIC
SUPPLY
PHASE
ENABLE
1
2
3
4
LOGIC
5
6
7
8
V
BB
V
CC
12
11
10
9
GROUND
SENSE
OUTA
LOAD
SUPPLY
V
BB
16
15
14
13
LOAD
SUPPLY
OUTB
MODE
GROUND
Data Sheet
29319.1†
Designed for bidirectional pulse-width modulated current control of
inductive loads, the A3952S– is capable of continuous output currents
to
±2
A and operating voltages to 50 V. Internal fixed off-time PWM
current-control circuitry can be used to regulate the maximum load
current to a desired value. The peak load current limit is set by the
user’s selection of an input reference voltage and external sensing
resistor. The fixed OFF-time pulse duration is set by a user-selected
external RC timing network. Internal circuit protection includes thermal
shutdown with hysteresis, transient suppression diodes, and crossover-
current protection. Special power-up sequencing is not required.
With the ENABLE input held low, the PHASE input controls load
current polarity by selecting the appropriate source and sink driver pair.
The MODE input determines whether the PWM current-control circuitry
operates in a slow current-decay mode (only the selected sink driver
switching) or in a fast current-decay mode (selected source and sink
switching). A user-selectable blanking window prevents false triggering
of the PWM current control circuitry. With the ENABLE input held high,
all output drivers are disabled. A sleep mode is provided to reduce
power consumption when inactive.
When a logic low is applied to the BRAKE input, the braking
function is enabled. This overrides ENABLE and PHASE to turn OFF
both source drivers and turn ON both sink drivers. The brake function
can be safely used to dynamically brake brush dc motors.
The A3952S– is supplied in a choice of four power packages. In all
package styles, the batwing/power tab is at ground potential and needs
no isolation. These devices are also available for operation from -40°C
to +125°C. To order, change the suffix from 'S–' to 'K–'.
Dwg. PP-056
Note that the A3952SB (DIP) and the A3952SLB
(SOIC) are electrically identical and share a
common terminal number assignment.
ABSOLUTE MAXIMUM RATINGS
Load Supply Voltage, V
BB
..................
50 V
Output Current, I
OUT
(t
w
≤
20
µs)
..................................
±
3.5 A
(Continuous) ...............................
±
2.0 A
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
......................
1.5 V
Reference Voltage, V
REF
....................
15 V
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, heat sinking and/or forced
cooling. 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 device thermal shutdown
circuitry. These conditions can be tolerated but
should be avoided.
FEATURES
s
s
s
s
s
s
s
s
s
±2
A Continuous Output Current Rating
50 V Output Voltage Rating
Internal PWM Current Control
Fast and Slow Current-Decay Modes
Sleep (Low Current Consumption) Mode
Internal Transient Suppression Diodes
Under-Voltage Lockout
Internal Thermal Shutdown Circuitry
Crossover-Current Protection
Always order by complete part number:
Part Number
A3952SB
A3952SEB
A3952SLB
A3952SW
Package
16-Pin DIP
28-Lead PLCC
16-Lead SOIC
12-Pin Power-Tab SIP
R
θJA
43°C/W
42°C/W
67°C/W
36°C/W
R
θJT
6.0°C/W
6.0°C/W
6.0°C/W
2.0°C/W
3952
FULL-BRIDGE
PWM MOTOR DRIVER
FUNCTIONAL BLOCK DIAGRAM
LOAD
SUPPLY
OUTA
OUTB
MODE
PHASE
UVLO
& TSD
EMITTERS
'EB' ONLY
ENABLE
BRAKE
LOGIC
SUPPLY
REF
1.5 V
9R
V
CC
R
Q
BLANKING
S
PWM LATCH
+ –
R
GROUND
VTH
RT
TRUTH TABLE
10
ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS
'W' TAB
'B' , 'EB', & 'LB' TAB
BRAKE ENABLE PHASE
H
H
H
H
H
H
L
L
L
L
X
X
X = Irrelevant
NOTES:
MODE
H
L
H
L
H
L
H
L
8
X
X
H
H
L
L
X
X
6
H
'W' AMBIENT
4
'B' & 'EB' AMBIENT
'LB' AMBIENT
H
L
L
2
0
25
50
75
100
125
Dwg. GP-007-1A
150
TEMPERATURE IN
°C
Z = High Impedance (source and sink both OFF)
1. Includes active pull-offs for power outputs.
2. Includes internal default V
sense
level for over-current protection.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 1994, 2001 Allegro MicroSystems, Inc.
–
+
V
CC
INPUT LOGIC
V
BB
SLEEP &
STANDBY MODES
SENSE
'B', 'LB', & 'W'
PACKAGES
RS
RC
CT
Dwg. FP-036
OUT
A
Z
Z
H
H
L
L
L
L
OUT
B
Z
Z
L
L
H
H
L
L
DESCRIPTION
Sleep Mode
Standby, Note 1
Forward,
Fast-Decay Mode
Forward,
Slow-Decay Mode
Reverse,
Fast-Decay Mode
Reverse,
Slow-Decay Mode
Brake,
Fast-Decay Mode
Brake, No Current
Control, Note 2
3952
FULL-BRIDGE
PWM MOTOR DRIVER
NO
CONNECTION
A3952SEB
LOAD
SUPPLY
BRAKE
MODE
RC
OUT B
REF
A3952SW
28
27
26
3
4
2
1
GROUND
5
6
7
8
9
10
V
BB
LOGIC
25
24
23
22
21
20
19
V
CC
GROUND
V
BB
GROUND
11
GROUND
1
13
16
12
15
17
14
18
2
OUTB
3
LOAD
SUPPLY
4
BRAKE
5
REF
6
RC
7
LOGIC
SUPPLY
V
CC
LOGIC
8
PHASE
9
ENABLE
10
MODE
11
OUTA
12
SENSE
EMITTERS
Dwg. PP-057
GROUND
LOGIC
SUPPLY
LOAD
SUPPLY
ENABLE
PHASE
OUTA
SENSE
ELECTRICAL CHARACTERISTICS at T
A
= +25
°
C, V
BB
= 50 V, V
CC
= 5.0 V, V
BRAKE
= 2.0 V,
V
SENSE
= 0 V, RC = 20 k
Ω
/1000 pF to Ground (unless noted otherwise).
Limits
Characteristic
Output Drivers
Load Supply Voltage Range
Output Leakage Current
V
BB
I
CEX
Operating, I
OUT
=
±2.0
A, L = 3 mH
V
OUT
= V
BB
V
OUT
= 0 V
Output Saturation Voltage
V
CE(SAT)
Source Driver, I
OUT
= -0.5 A
Source Driver, I
OUT
= -1.0 A
Source Driver, I
OUT
= -2.0 A
Sink Driver, I
OUT
= +0.5 A
Sink Driver, I
OUT
= +1.0 A
Sink Driver, I
OUT
= +2.0 A
Clamp Diode Forward Voltage
(Source or Sink)
V
F
I
F
= 0.5 A
I
F
= 1.0 A
I
F
= 2.0 A
Load Supply Current
(No Load)
I
BB(ON)
I
BB(OFF)
V
ENABLE
= 0.8 V
V
ENABLE
= 2.0 V, V
MODE
= 0.8 V
V
BRAKE
= 0.8 V
I
BB(SLEEP)
V
ENABLE
= V
MODE
= 2.0 V
V
CC
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
<1.0
<-1.0
0.9
1.0
1.2
0.9
1.0
1.3
1.0
1.1
1.4
2.9
3.1
3.1
<1.0
Symbol
Test Conditions
Min.
Typ.
Dwg. PP-058
Max.
Units
50
50
-50
1.2
1.4
1.8
1.2
1.4
1.8
1.4
1.6
2.0
6.0
6.5
6.5
50
V
µA
µA
V
V
V
V
V
V
V
V
V
mA
mA
mA
µA
Continued next page …
3952
FULL-BRIDGE
PWM MOTOR DRIVER
Limits
Characteristic
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 Voltage Range
Reference Input Current
Reference Voltage Divider Ratio
Comparator Input Offset Voltage
PWM RC Fixed OFF Time
PWM Minimum ON Time
V
REF
I
REF
–
V
IO
t
off
t
on(min)
V
IN
= 2.0 V
V
IN
= 0.8 V
Operating
V
REF
= 2.0 V
V
REF
= 15 V
V
REF
= 0 V
C
T
= 1000 pF, R
T
= 20 kΩ
C
T
= 820 pF, R
T
≥
12 kΩ
C
T
= 1200 pF, R
T
≥
12 kΩ
Propagation Delay Time
t
pd
I
OUT
=
±2.0
A, 50% E
IN
to 90% E
OUT
Transition:
ENABLE ON to Source ON
ENABLE OFF to Source OFF
ENABLE ON to Sink ON
ENABLE OFF to Sink OFF
PHASE Change to Source ON
PHASE Change to Source OFF
PHASE Change to Sink ON
PHASE Change to Sink OFF
t
pd(pwm)
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
UVLO Disable Threshold
UVLO Hysteresis
Logic Supply Current
(No Load)
T
J
∆T
J
V
CC(UVLO)
∆V
CC(UVLO)
I
CC(ON)
I
CC(OFF)
I
CC(BRAKE)
I
CC(SLEEP)
V
ENABLE
= 0.8 V, V
BRAKE
= 2.0 V
V
ENABLE
= 2.0 V, V
MODE
= 0.8 V
V
BRAKE
= 0.8 V
V
ENABLE
= V
MODE
= V
BRAKE
= 2.0 V
Comparator Trip to Sink OFF
–
–
–
–
–
–
–
–
–
–
–
3.15
300
–
–
–
–
2.9
0.7
2.4
0.7
2.9
0.7
2.4
0.7
0.8
165
15
3.50
400
20
12
26
3.0
–
–
–
–
–
–
–
–
1.5
–
–
3.85
500
30
18
40
5.0
µs
µs
µs
µs
µs
µs
µs
µs
µs
°C
°C
V
mV
mA
mA
mA
mA
Operating
4.5
2.0
–
–
–
0
25
9.5
–
18
–
–
5.0
–
–
<1.0
<-2.0
–
40
10.0
±1.0
20
1.7
2.5
5.5
–
0.8
20
-200
15
55
10.5
±10
22
3.0
3.8
V
V
V
µA
µA
V
µA
–
mV
µs
µs
µs
Symbol
Test Conditions
Min.
Typ.
Max.
Units
NOTES: 1. Typical Data is for design information only.
2. Each driver is tested separately.
3. 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
3952
FULL-BRIDGE
PWM MOTOR DRIVER
FUNCTIONAL DESCRIPTION
INTERNAL PWM CURRENT CONTROL DURING
FORWARD AND REVERSE OPERATION
The A3952S– 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 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
). The internal circuitry compares the voltage
across the external sense resistor to one tenth the voltage
on the REF input terminal, resulting in a function approxi-
mated by
I
TRIP
= V
REF
/(10R
S
).
In forward or reverse mode the current-control circuitry
limits the load current. When the load current reaches
I
TRIP
, the comparator resets a latch to turn OFF the
selected sink driver (in the slow-decay mode) or selected
sink and source driver pair (in the fast-decay mode). In
slow-decay mode, the selected sink driver is disabled; the
load inductance causes the current to recirculate through
the source driver and flyback diode (see figure 1). In fast-
decay mode, the selected sink and source driver pair are
disabled; the load inductance causes the current to flow
from ground to the load supply via the ground clamp and
flyback diodes.
V
BB
ENABLE
MODE
I
TRIP
RC
LOAD
CURRENT
RC
Dwg. WP-015-1
Figure 2 — Slow and Fast Current-Decay Waveforms
INTERNAL PWM CURRENT CONTROL DURING
BRAKE MODE OPERATION
The brake circuit turns OFF both source drivers and
turns ON both sink drivers. For dc motor applications, this
has the effect of shorting the motor’s back-EMF voltage,
resulting in current flow that brakes the motor dynamically.
However, if the back-EMF voltage is large, and there is no
PWM current limiting, then the load current can increase to
a value that approaches a locked rotor condition. To limit
the current, when the I
TRIP
level is reached, the PWM
circuit disables the conducting sink driver. The energy
stored in the motor’s inductance is then discharged into
the load supply causing the motor current to decay.
As in the case of forward/reverse operation, the drivers
are re-enabled after a time given by t
off
= R
T
C
T
(see “RC
Fixed OFF Time” below). Depending on the back-EMF
voltage (proportional to the motor’s decreasing speed), the
load current again may increase to I
TRIP
. If so, the PWM
cycle will repeat, limiting the load current to the desired
value.
Brake Operation - MODE Input High
During braking, when the MODE input is high, the
current limit can be approximated by
DRIVE CURRENT
RECIRCULATION
(SLOW-DECAY MODE)
RECIRCULATION
(FAST-DECAY MODE)
RS
Dwg. EP-006-2A
I
TRIP
= V
REF
/(10R
S
).
CAUTION:
Because the kinetic energy stored in the
motor and load inertia is being converted into current,
which charges the V
BB
supply bulk capacitance (power
supply output and decoupling capacitance), care must be
taken to ensure the capacitance is sufficient to absorb the
energy without exceeding the voltage rating of any devices
connected to the motor supply.
Figure 1 — Load-Current Paths
The user selects an external resistor (R
T
) and capaci-
tor (C
T
) to determine the time period (t
off
= R
T
C
T
) during
which the drivers remain disabled (see “RC Fixed OFF
Time” below). At the end of the R
T
C
T
interval, the drivers
are re-enabled allowing the load current to increase again.
The PWM cycle repeats, maintaining the load current at
the desired value (see figure 2).
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