3973
PRELIMINARY INFORMATION
(Subject to change without notice)
December 1, 2000
CHARGE
PUMP
DUAL DMOS FULL-BRIDGE MICRO-
STEPPING PWM MOTOR DRIVER
Designed for pulse-width modulated (PWM) current control of
bipolar microstepping stepper motors, the A3973SB and A3973SLB are
capable of continuous output currents to
鹵1
A and operating voltages to
35 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. The A3973SB (DIP) and the A3973SLB (SOIC)
are electrically identical and differ only in package style.
The desired load-current level is set via the serial port with two 6-bit
linear DACs in conjunction with a reference voltage. The six bits of
control allow maximum flexibility in torque control for a variety of step
methods, from microstepping to full-step drive. Load current is set in
1.56% increments of the maximum value.
Synchronous rectification circuitry allows the load current to flow
through the low
r
DS(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 hyster-
esis, transient-suppression diodes, and crossover-current protection.
Special power-up sequencing is not required.
The A3973SB is supplied in a 24-lead plastic DIP with a copper
batwing power tab; the A3973SLB is supplied in a 24-lead plastic SOIC
with a copper batwing power tab for surface-mount applications. The
power tabs are at ground potential and need no electrical isolation.
Data Sheet
29319.34
VCP
CP1
CP2
OUT
1B
LOAD
SUPPLY
1
GROUND
GROUND
SENSE
1
OUT
1A
STROBE
CLOCK
DATA
1
2
3
4
5
6
7
8
9
9
10
11
12
24
23
22
21
20
19
18
17
16
OSC
SLEEP
V
REG
OUT
2B
LOAD
SUPPLY
2
GROUND
GROUND
SENSE
2
OUT
2A
LOGIC
SUPPLY
MUX
REF
6-BIT DAC
& LOGIC
6-BIT DAC
& LOGIC
V
BB1
V
BB2
SERIAL PORT
V
DD
15
14
13
Dwg. PP-069-3
ABSOLUTE MAXIMUM RATINGS
at T
A
= +25擄C
Load Supply Voltage, V
BB
................
35 V
Output Current, I
OUT
......................
鹵1.0
A
Logic Supply Voltage, V
DD
..............
7.0 V
Logic Input Voltage Range,
V
IN
................
-0.3 V to V
DD
+ 0.3 V
Reference Voltage, V
REF
.....................
3 V
Sense Voltage (dc), V
S
................
500 mV
Package Power Dissipation, P
D
A3973SB ...............................
3.1 W
A3973SLB ............................
2.2 W
Operating Temperature Range,
T
A
..........................
-20擄C to +85擄C
Junction Temperature, T
J
.............
+150擄C
Storage Temperature Range,
T
S
.........................
-55擄C to +150擄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 tempera-
ture of 150擄C.
FEATURES
I
I
I
I
I
I
I
I
I
I
I
I
鹵1
A, 35 V Continuous Output Rating
Low
r
DS(on)
DMOS Output Drivers
Optimized Microstepping via 6-Bit Linear DACs
Programmable Mixed, Fast, and Slow Current-Decay Modes
4 MHz Internal Oscillator for Digital Timing
Serial-Interface Controls Chip Functions
Synchronous Rectification for Low Power Dissipation
Internal UVLO and Thermal Shutdown Circuitry
Crossover-Current Protection
Precision 2 V Reference
Inputs Compatible with 3.3 V or 5 V Control Signals
Sleep and Idle Modes
Always order by complete part number, e.g.,
A3973SB
.
ALLEGRO
1
2
3
4
5
6
7
8
9
10
11
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