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What is A3951?

This electronic component, produced by the manufacturer "Allegro MicroSystems", performs the same function as "FULL-BRIDGE PWM MOTOR DRIVER".


A3951 Datasheet PDF - Allegro MicroSystems

Part Number A3951
Description FULL-BRIDGE PWM MOTOR DRIVER
Manufacturers Allegro MicroSystems 
Logo Allegro MicroSystems Logo 


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3951
FULL-BRIDGE PWM MOTOR DRIVER
A3951SB
NC 1
REF/BRAKE 2
VBB
RC 3
GROUND 4
GROUND 5
LOGIC
SUPPLY
6
VCC
PHASE 7
ENABLE 8
LOGIC
VBB
16
LOAD
SUPPLY
15 OUTB
14 GROUND
13 GROUND
12 GROUND
11 SENSE
10 OUTA
LOAD
9 SUPPLY
Dwg. PP-056-1
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 ....................... VCC
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 A3951SB and A3951SW are 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. The A3951SB and A3951SW are improved replacements for
the UDN2953B and UDN2954W, respectively. For new system de-
signs, the A3952SB/SEB/SLB/SW are recommended.
With the ENABLE input held low, the PHASE input controls load
current polarity by selecting the appropriate source and sink driver pair.
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.
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 A3951SB is supplied in a 16-pin dual in-line plastic package
with copper heat-sink contact tabs. The lead configuration enables
easy attachment of a heat sink while fitting a standard printed wiring
board layout. The A3951SW, for higher package power dissipation
requirements, is supplied in a 12-pin single in-line power-tab package.
In either package style, the batwing/power tab is at ground potential
and needs no isolation.
FEATURES
I ±2 A Continuous Output Current Rating
I 50 V Output Voltage Rating
I Internal PWM Current Control
I Internal Transient Suppression Diodes
I Under-Voltage Lockout
I Internal Thermal Shutdown Circuitry
I Crossover-Current Protection
I Default Brake Current Limit
Always order by complete part number:
Part Number
Package
A3951SB
A3951SW
16-Pin DIP
12-Pin Power-Tab SIP
RθJA
43°C/W
36°C/W
RθJT
6.0°C/W
2.0°C/W

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A3951 equivalent
3951
FULL-BRIDGE
PWM MOTOR DRIVER
FUNCTIONAL DESCRIPTION
INTERNAL PWM CURRENT CONTROL DURING
FORWARD AND REVERSE OPERATION
The A3951SB/SW 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 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
approximated by
ITRIP = VREF/(10RS).
In forward or reverse mode the current-control cir-
cuitry limits the load current. When the load current
reaches ITRIP, the comparator resets a latch to turn off the
selected sink driver. The load inductance causes the
current to recirculate through the source driver and
flyback diode (two-quadrant operation or slow decay).
See figure 1.
VBB
RS
DRIVE CURRENT
RECIRCULATION
Dwg. EP-006-9
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
Timebelow). 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
I TRIP
LOAD
CURRENT
RC
Dwg. WP-015-3
Figure 2 Load-Current Waveform
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 motors 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 motors 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 Timebelow). Depending on the back-EMF
voltage (proportional to the motors 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
During braking, the peak current limit defaults inter-
nally to a value approximated by
ITRIP = 1.5 V/RS.
In this mode, the value of RS determines the ITRIP value
independent of VREF. This is useful in applications with
differing run and brake currents and no practical method of
varying VREF.
www.allegromicro.com
5


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Part Details

On this page, you can learn information such as the schematic, equivalent, pinout, replacement, circuit, and manual for A3951 electronic component.


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