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PDF A3974 Data sheet ( Hoja de datos )
| Número de pieza | A3974 | |
| Descripción | Dual Dmos Full-bridge Microstepping PWM Motor Driver | |
| Fabricantes | Allegro Micro Systems | |
| Logotipo |  |
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3974
NC 7
STROBE 8
CLOCK 9
DATA 10
GND 11
GND 12
GND 13
REF1 14
÷
REF2 15
LOGIC
SUPPLY 16 VDD
NC 17
÷
VBB1
PROGRAM
PWM TIMER
LOGIC
PROGRAM
PWM TIMER
LOGIC
VBB2
39 NC
38 CP2
37 CP1
36 CP
35 GND
34 GND
33 GND
32 OSC
31 SLEEP
30 VREG
29 NC
Dwg. PP-073
ABSOLUTE MAXIMUM RATINGS
at TA = +25°C
Load Supply Voltage, VBB ............................ 50 V
Output Current, IOUT .................................. ±1.5 A
Logic Supply Voltage, VDD .......................... 7.0 V
Logic Input Voltage Range, VIN
Continous ................... -0.3 V to VDD + 0.3 V
tW < 30 ns ................... -1.0 V to VDD + 1.0 V
Reference Voltage, VREF ................................. 3 V
Sense Voltage (dc), VS
Continous .............................................. 0.5 V
tW < 1 µs ................................................ 2.5 V
Package Power Dissipation, PD .................. 3.9 W
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, and heat sinking. Under any set
of conditions, do not exceed the specified current rating
or a junction temperature of 150°C.
DMOS DUAL FULL-BRIDGE
PWM MOTOR DRIVER
Designed for pulse-width modulated (PWM) current control
of two dc motors, the A3974SED is capable of output currents to
±1.5 A and operating voltages to 50 V. Internal fixed off-time
PWM current-control timing circuitry can be programmed via a
serial interface to operate in slow, fast, and mixed current-decay
modes.
Independant ENABLE input terminals are provided for use in
controlling the speed and torque of each dc motor with externally
applied PWM control signals.
Synchronous rectification circuitry allows the load current to
flow through the low rDS(on) of the DMOS output driver during
the current decay. This feature will eliminate the need for
external clamp diodes in most applications, saving cost and
external component count, while minimizing power dissipation.
Internal circuit protection includes thermal shutdown with
hysteresis, undervoltage monitoring of VDD and the charge
pump, and crossover-current protection. Special power-up
sequencing is not required.
The A3974SED is supplied in a 44-lead plastic PLCC with
four copper batwing tabs for maximum heat dissipation. The
power tabs are at ground potential and need no electrical isola-
tion.
FEATURES
s ±1.5 A, 50 V Continuous Output Rating
s Low rDS(on) DMOS Output Drivers
s Programmable Slow, Fast, and Mixed Current-Decay Modes
s Serial-Interface Controls Chip Functions
s Synchronous Rectification for Low Power Dissipation
s Internal UVLO and Thermal Shutdown Circuitry
s Crossover-Current Protection
s Sleep and Idle Modes
Always order by complete part number: A3974SED .
1 page  
3974
DMOS DUAL FULL-BRIDGE
PWM MOTOR DRIVER
FUNCTIONAL DESCRIPTION
Serial Interface. The A3974SED is controlled via a 3-wire
(clock, data,strobe) serial port. The programmable functions
allow maximum flexibility in configuring the PWM to the
motor drive requirements. The serial data is written as two 20-
bit words: 1 bit to select the word and 19 bits of data. The data
is clocked in starting with D19.
Word 0 Bit Assignments
Select Word 0 (D18 = 0)
Bit Function
D0 Bridge 1 blank time LSB
D1 Bridge 1 blank time MSB
D2 Bridge 1 off-time LSB
D3 Bridge 1 off-time bit 1
D4 Bridge 1 off-time bit 2
D5 Bridge 1 off-time bit 3
D6 Bridge 1 off-time MSB
D7 Bridge 1 fast-decay time bit LSB
D8 Bridge 1 fast-decay time bit 1
D9 Bridge 1 fast-decay time bit 2
D10 Bridge 1 fast-decay time MSB
D11 Bridge 1 sync. rect. control
D12 Bridge 1 sync. rect. control
D13 Bridge 1 external PWM mode
D14 Bridge 1 enable
D15 Bridge 1 phase
D16 Bridge 1 reference range select
D17 Bridge 1 internal PWM mode
D18 Word select = 0
D19 Test mode
D0 – D1 Blank Time. The current-sense comparator is
blanked when any output driver is switched on, according to the
table below. fosc is the oscillator input frequency.
D1 D0
00
01
10
11
Blank Time
4/fOSC
6/fOSC
12/fOSC
24/fOSC
D2 – D6 Fixed Off Time. This five-bit word sets the fixed
off-time for the internal PWM control circuitry. The off-time is
defined by
toff =(8 [1 + N]/fOSC) - 1/fOSC
where N = 0 .... 31
For example, with an oscillator frequency of 4 MHz, the
fixed off-time will be adjustable from 1.75 µs to 63.75 µs in
increments of 2 µs.
D7 – D10 Fast Decay Time. This four-bit word sets the fast-
decay portion of the fixed off-time for the internal PWM control
circuitry. This will only have impact if mixed-decay mode is
selected (via bit D17). For tfd > toff, the device will effectively
operate in fast-decay mode. The fast-decay portion is defined
by
tfd = (8[1 + N]/fOSC] - 1/fOSC
where N = 0 .... 15
For example, with an oscillator frequency of 4 MHz, the fast-
decay time will be adjustable from 1.75 µs to 31.75 µs in
increments of 2 µs.
D11 – D12 Synchronous Rectification.
D12 D11
00
01
10
11
Synchronous Rectifier
Disabled
Low side only
Active
Passive
The different modes of operation are described in the synchro-
nous rectification section of the functional description.
D13 External PWM Decay Mode. This bit determines the
current-decay mode when using ENABLE chopping for
external PWM current control.
D13 Mode
0 Fast
1 Slow
continued next page ...
www.allegromicro.com
5
5 Page 
3974
DMOS DUAL FULL-BRIDGE
PWM MOTOR DRIVER
Dimensions in Millimeters
(for reference only)
28 18
8.10
7.39
0.533
0.331
8.10
7.39
1.27
BSC
29
0.812
0.661
17.65
17.40
16.662
16.510
39
17
INDEX AREA
7
0.51
MIN
4.57
4.20
40 44 1 2
16.662
16.510
17.65
17.40
6
Dwg. MA-005-44A mm
NOTES: 1. Lead spacing tolerance is non-cumulative.
2. Exact body and lead configuration at vendor’s option within limits shown.
3. Available in standard sticks/tubes of 28 devices or add “TR” to part number for tape and reel.
www.allegromicro.com
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet A3974.PDF ] | |
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