3952 Datasheet PDF - Allegro MicroSystems
| Part Number | 3952 | |
| Description | FULL-BRIDGE PWM MOTOR DRIVER | |
| Manufacturers | Allegro MicroSystems | |
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3952
FULL-BRIDGE PWM MOTOR DRIVER
A3952SB
BRAKE 1
REF 2
VBB
RC 3
GROUND 4
GROUND 5
LOGIC
SUPPLY
6
VCC
PHASE 7
ENABLE 8
LOGIC
VBB
16
LOAD
SUPPLY
15 OUTB
14 MODE
13 GROUND
12 GROUND
11 SENSE
10 OUTA
LOAD
9 SUPPLY
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, VBB .................. 50 V
Output Current, IOUT
(tw ≤ 20 µs) .................................. ±3.5 A
(Continuous) ............................... ±2.0 A
Logic Supply Voltage, VCC ................. 7.0 V
Logic Input Voltage Range,
VIN ....................... -0.3 V to VCC + 0.3 V
Sense Voltage, VSENSE ...................... 1.5 V
Reference Voltage, VREF .................... 15 V
Package Power Dissipation,
PD ....................................... See Graph
Operating Temperature Range,
TA ............................... –20°C to +85°C
Junction Temperature, TJ ............. +150°C*
Storage Temperature Range,
TS ............................. –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.
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–'.
FEATURES
s ±2 A Continuous Output Current Rating
s 50 V Output Voltage Rating
s Internal PWM Current Control
s Fast and Slow Current-Decay Modes
s Sleep (Low Current Consumption) Mode
s Internal Transient Suppression Diodes
s Under-Voltage Lockout
s Internal Thermal Shutdown Circuitry
s 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
RθJA
43°C/W
42°C/W
67°C/W
36°C/W
RθJT
6.0°C/W
6.0°C/W
6.0°C/W
2.0°C/W
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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 (ITRIP) is set by the selection of an
external current sensing resistor (RS) and reference input
voltage (VREF). 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
ITRIP = VREF/(10RS).
In forward or reverse mode the current-control circuitry
limits the load current. When the load current reaches
ITRIP, 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
DRIVE CURRENT
RECIRCULATION
(SLOW-DECAY MODE)
RECIRCULATION
(FAST-DECAY MODE)
RS
Dwg. EP-006-2A
Figure 1 — Load-Current Paths
The user selects an external resistor (RT) and capaci-
tor (CT) to determine the time period (toff = RTCT) during
which the drivers remain disabled (see “RC Fixed OFF
Time” below). At the end of the RTCT 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).
ENABLE
MODE
I TRIP
LOAD
CURRENT
RC
RC
Dwg. WP-015-1
Figure 2 — Fast and Slow 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 ITRIP 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 toff = RTCT (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 ITRIP. 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
ITRIP = VREF/(10RS).
CAUTION: Because the kinetic energy stored in the
motor and load inertia is being converted into current,
which charges the VBB 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.
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| Information | Total 16 Pages | |
| Link URL | [ Copy URL to Clipboard ] | |
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