SERIAL PORT
6-BIT DAC
& LOGIC
24
23
22
21
20
19
18
17
16
15
14
13
GROUND
GROUND
SLEEP
VREG
OUT2B
LOAD
SUPPLY2
SENSE2
OUT2A
LOGIC
SUPPLY
MUX
REF
VDD
Dwg. PP-069-3
1
2
3
4
5
6
7
8
9
12
11
10
9
GROUND
GROUND
VCP
CP1
CP2
OUT1B
OUT1A
STROBE
CLOCK
DATA
SENSE1
LOAD
SUPPLY1
CHARGE
PUMP
OSC
VBB2VBB1
6-BIT DAC
& LOGIC
Data Sheet
29319.34
3973
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 ±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.
FEATURES
a73 ±1 A, 35 V Continuous Output Rating
a73 Low r
DS(on)
DMOS Output Drivers
a73 Optimized Microstepping via 6-Bit Linear DACs
a73 Programmable Mixed, Fast, and Slow Current-Decay Modes
a73 4 MHz Internal Oscillator for Digital Timing
a73 Serial-Interface Controls Chip Functions
a73 Synchronous Rectification for Low Power Dissipation
a73 Internal UVLO and Thermal Shutdown Circuitry
a73 Crossover-Current Protection
a73 Precision 2 V Reference
a73 Inputs Compatible with 3.3 V or 5 V Control Signals
a73 Sleep and Idle Modes
PRELIMINARY INFORMATION
(Subject to change without notice)
December 1, 2000
ABSOLUTE MAXIMUM RATINGS
at T
A
= +25°C
Load Supply Voltage, V
BB
................ 35 V
Output Current, I
OUT
...................... ±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°C to +85°C
Junction Temperature, T
J
............. +150°C
Storage Temperature Range,
T
S
......................... -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 tempera-
ture of 150°C.
Always order by complete part number, e.g., A3973SB .