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3952 Schematic ( PDF Datasheet ) - Allegro MicroSystems

Teilenummer 3952
Beschreibung FULL-BRIDGE PWM MOTOR DRIVER
Hersteller Allegro MicroSystems
Logo Allegro MicroSystems Logo 




Gesamt 16 Seiten
3952 Datasheet, Funktion
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






3952 Datasheet, Funktion
3952
FULL-BRIDGE
PWM MOTOR DRIVER
Brake Operation - MODE Input Low
During braking, with the MODE input low, the peak
current limit defaults internally 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.
Choosing a small value for RS essentially disables the
current limiting during braking. Therefore, care should be
taken to ensure that the motor’s current does not exceed
the absolute maximum ratings of the device. The braking
current can be measured by using an oscilloscope with a
current probe connected to one of the motors leads.
RC Fixed OFF Time
The internal PWM current control circuitry uses a one
shot to control the time the driver(s) remain(s) OFF. The
one shot time, toff (fixed OFF time), is determined by the
selection of an external resistor (RT) and capacitor (CT)
connected in parallel from the RC terminal to ground. The
fixed OFF time, over a range of values of CT = 820 pF to
1500 pF and RT = 12 kto 100 k, is approximated by
toff = RTCT.
When the PWM latch is reset by the current compara-
tor, the voltage on the RC terminal will begin to decay from
approximately 3 volts. When the voltage on the RC
terminal reaches approximately 1.1 volt, the PWM latch is
set, thereby re-enabling the driver(s).
RC Blanking
In addition to determining the fixed OFF-time of the
PWM control circuit, the CT component sets the compara-
tor 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, BRAKE, 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 toff
time, the comparators output is blanked and CT begins to
be charged from approximately 1.1 V by an internal current
source of approximately 1 mA. The comparator output
remains blanked until the voltage on CT reaches approxi-
mately 3.0 volts.
Similarly, when a transition of the PHASE input occurs,
CT 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, CT is charged by an internal
current source of approximately 1 mA. The comparator
output remains blanked until the voltage on CT reaches
approximately 3.0 volts.
Similarly, when the device is disabled via the ENABLE
input, CT is discharged to near ground. When the device is
re-enabled, CT is charged by the internal current source.
The comparator output remains blanked until the voltage
on CT reaches approximately 3.0 V.
For applications that use the internal fast-decay mode
PWM operation, the minimum recommended value is CT =
1200 pF ±5 %. For all other applications, the minimum
recommended value is CT = 820 pF ±5 %. These values
ensure 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
values for CT are recommended and the value of RT can
be sized to determine toff. For more information regarding
load current regulation, see below.
LOAD CURRENT REGULATION WITH THE INTERNAL
PWM CURRENT-CONTROL CIRCUITRY
When the device is operating in slow-decay mode,
there is a limit to the lowest level that the PWM current-
control circuitry can regulate load current. The limitation is
the minimum duty cycle, which is a function of the user-
selected value of toff and the maxuimum value of the
minimum ON-time pulse, ton(min), 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, or a brush dc
motor when stalled or at startup, the worst-case value of
current regulation can be approximated by
I(AV)
[(VBB
VSAT(source+sink)) ton(min)max] [1.05 (VSAT(sink)
1.05 (ton(min)max + toff) RLOAD
+
VD)
toff]
where toff = RTCT, RLOAD is the series resistance of the
load, VBB is the load/motor supply voltage, and ton(min)max
is specified in the electrical characteristics table. When
the motor is rotating, the back EMF generated will influ-
ence the above relationship. For brush dc motor applica-
tions, the current regulation is improved. For stepper
motor applications when the motor is rotating, the effect is
more complex. A discussion of this subject is included in
the section on stepper motors under Applications.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000

6 Page









3952 pdf, datenblatt
3952
FULL-BRIDGE
PWM MOTOR DRIVER
0.013
0.021
0.219
0.191
0.050
BSC
0.219
0.191
A3952SEB
Dimensions in Inches
(controlling dimensions)
18
19
0.026
0.032
0.456
0.450
0.495
0.485
25
12
11
INDEX AREA
5
0.020
MIN
0.165
0.180
26 28 1
0.456
0.450
0.495
0.485
4
Dwg. MA-005-28A in
Dimensions in Millimeters
(for reference only)
18
12
0.331
0.533
5.56
4.85
1.27
BSC
5.56
4.85
19
0.812
0.661
11.58
11.43
12.57
12.32
25
11
INDEX AREA
5
0.51
MIN
4.57
4.20
26 28 1
11.582
11.430
12.57
12.32
NOTES: 1. Index is centered on “D” side.
2. Webbed lead frame. Leads indicated are internally one piece.
3. Lead spacing tolerance is non-cumulative.
4. Exact body and lead configuration at vendor’s option within limits shown.
5. Intended to meet new JEDEC Standard when that is approved.
4
Dwg. MA-005-28A mm
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000

12 Page





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