A3984
DMOS Microstepping Driver with Translator
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.
Package LP
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
GND
24
CP1
CP2
1
2
ENABLE
23
lines, or complex interfaces to program. The A3984 interface is an ideal
OUT2B
22
VCP
3
fit for applications where a complex microprocessor is unavailable or is
overburdened.
VBB2
21
VREG
MS1
4
SENSE2
20
5
The chopping control in the A3984 automatically selects the current
MS2
OUT2A
OUT1A
SENSE1
VBB1
6
19
18
17
16
15
14
13
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.
RESET
ROSC
SLEEP
VDD
7
8
9
OUT1B
DIR
10
11
12
STEP
REF
GND
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.
Approximate Scale 1:1
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.
ABSOLUTE MAXIMUM RATINGS
Load Supply Voltage,VBB ...................................35 V
Output Current, IOUT.........................................±2 A*
Logic Input Voltage, VIN ..................... –0.3 V to 7 V
Sense Voltage, VSENSE .......................................0.5 V
Reference Voltage, VREF ………..........................4 V
Operating Temperature Range
Ambient, TA ................................. –20°C to 85°C
Junction Temperature, TJ(MAX).....................150°C
Storage Temperature, 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.
FEATURES
Low RDS(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
Selection Guide
Part Number
A3984SLP-T
Pb-free*
Yes
Package
24-pin TSSOP
24-pin TSSOP
Packing
62 per tube
4000 per reel
A3984SLPTR-T
Yes
*Pb-based variants are being phased out of the product line. The variants cited in this
footnote are in production but have been determined to be LAST TIME BUY.
This classification indicates that sale of this device is currently restricted to existing
customer applications. The variants should not be purchased for new design applications
because obsolescence in the near future is probable. Samples are no longer available.
Status change: October 31, 2006. Deadline for receipt of LAST TIME BUY orders:
April 27, 2007. These variants include: A3984SLP and A3984SLPTR.
26184.30Bpb