A3984
DMOS Microstepping Driver with Translator
Package LP
CP1
CP2
VCP
VREG
MS1
MS2
RESET
ROSC
SLEEP
1
24 GND
2
3
23 ENABLE
22 OUT2B
21 VBB2
20 SENSE2
4
5
6
7
19 OUT2A
18 OUT1A
17 SENSE1
16 VBB1
15 OUT1B
14 DIR
13 GND
8
9
VDD 10
STEP 11
REF 12
Approximate Scale 1:1
ABSOLUTE MAXIMUM RATINGS
Load Supply Voltage,V
BB
...................................35
V
Output Current, I
OUT
.........................................
±2 A
*
Logic Input Voltage, V
IN
.....................
–0.3 V to 7 V
Sense Voltage, V
SENSE
.......................................0.5
V
Reference Voltage, V
REF
………..........................4
V
Operating Temperature Range
Ambient, T
A
.................................
–20°C to 85°C
Junction Temperature, T
J(MAX)
.....................
150°C
Storage Temperature, T
S
....................
–55°C to 150°C
The A3984 is a complete microstepping motor driver with built-in
translator for easy operation. It is designed to operate bipolar stepper
motors in full-, half-, quarter-, and sixteenth-step modes, with an output
drive capacity of up to 35 V and ±2 A. The A3984 includes a fixed off-
time current regulator which has the ability to operate in Slow or Mixed
decay modes.
The translator is the key to the easy implementation of the A3984.
Simply inputting one pulse on the STEP input drives the motor one
microstep. There are no phase sequence tables, high frequency control
lines, or complex interfaces to program. The A3984 interface is an ideal
fit for applications where a complex microprocessor is unavailable or is
overburdened.
The chopping control in the A3984 automatically selects the current
decay mode (Slow or Mixed). When a signal occurs at the STEP input
pin, the A3984 determines if that step results in a higher or lower
current in each of the motor phases. If the change is to a higher current,
then the decay mode is set to Slow decay. If the change is to a lower
current, then the current decay is set to Mixed (set initially to a fast
decay for a period amounting to 31.25% of the fixed off-time, then
to a slow decay for the remainder of the off-time). This current decay
control scheme results in reduced audible motor noise, increased step
accuracy, and reduced power dissipation.
Internal synchronous rectification control circuitry is provided to
improve power dissipation during PWM operation.
Internal circuit protection includes: thermal shutdown with hysteresis,
undervoltage lockout (UVLO), and crossover-current protection.
Special power-on sequencing is not required.
The A3984 is supplied in a low-profile (1.2 mm maximum), 24-pin
TSSOP with exposed thermal pad (package
LP).
It is also available
in a lead (Pb) free version (suffix
–T),
with 100% matte tin plated
leadframes.
Reg
Charge
Pump
Translator
& Control Logic
OSC
FEATURES
Low R
DS(ON)
outputs
Automatic current decay mode detection/selection
Mixed and Slow current decay modes
Synchronous rectification for low power dissipation
Internal UVLO and thermal shutdown circuitry
Crossover-current protection
*
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.
Use the following complete part number when ordering:
Part Number
A3984SLP
A3984SLP-T
Pb-free
–
Yes
Package
24-pin, TSSOP
Description
Exposed thermal pad
26184.30A
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
