A3979
Microstepping DMOS Driver with Translator
The A3979 is a complete microstepping motor driver with built-in
translator, designed as a pin-compatible replacement for the successful
A3977, with enhanced microstepping ( /16 step) precision. It is designed
Package LP, 28-pin TSSOP
with Exposed Thermal Pad
1
to operate bipolar stepper motors in full-, half-, quarter-, and sixteenth-
step modes, with an output drive capacity of up to 35 V and ±2.5 A. The
A3979 includes a fixed off-time current regulator that has the ability
to operate in Slow, Fast, or Mixed decay modes. This current-decay
control scheme results in reduced audible motor noise, increased step
accuracy, and reduced power dissipation.
1
2
28
VBB1
SENSE1
HOME
DIR
27
26
25
24
23
22
21
20
19
18
17
16
15
SLEEP
ENABLE
OUT1B
CP2
3
4
OUT1A
PFD
5
PWM
Timer
Charge
Pump
6
RC1
CP1
Translator
and
Control
Logic
The translator is the key to the easy implementation of the A3979. It
allows the simple input of one pulse on the STEP pin to drive the motor
one microstep, which can be either a full step, half, quarter, or sixteenth,
depending on the setting of the MS1 and MS2 logic inputs. There are no
phase-sequence tables, high-frequency control lines, or complex inter-
faces to program. The A3979 interface is an ideal fit for applications
where a complex microprocessor is unavailable or is overburdened.
7
AGND
REF
VCP
8
÷8
PGND
VREG
STEP
OUT2B
RESET
SR
9
RC2
Reg
10
11
12
13
VDD
OUT2A
MS2
MS1
SENSE2 14
VBB2
Internal synchronous-rectification control circuitry is provided to
improve power dissipation during PWM operation. Internal circuit
protection includes: thermal shutdown with hysteresis, UVLO (under-
voltage lockout), and crossover-current protection. Special power-on
sequencing is not required.
AGND and PGND must be
connected together externally.
Approximate Scale 1:1
The A3979 is supplied in a low-profile (maximum height ≤ 1.20 mm),
28-pin TSSOP with exposed thermal pad. The package is available in a
lead (Pb) free version, with 100% matte tin leadframe plating.
ABSOLUTE MAXIMUM RATINGS
Load Supply Voltage,VBB ...................................35 V
Output Current, IOUT......................................±2.5 A*
Logic Supply Voltage, VDD ...............................7.0 V
FEATURES
Logic Input Voltage Range, V
IN
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
±2.5 A, 35 V output rating
tW > 30 ns........................–0.3 V to VDD + 0.3 V
Low RDS(On) outputs: 0.28 Ω source, 0.22 Ω sink, typical
Automatic current decay mode detection/selection
3.0 to 5.5 V logic supply voltage range
Slow, Fast or Mixed current decay modes
Home output
Synchronous rectification for low power dissipation
Internal UVLO and thermal shutdown circuitry
Crossover-current protection
tW < 30 ns..............................–1 V to VDD + 1 V
Sense Voltage, VSENSE .......................................0.5 V
Reference Voltage, VREF ......................................VDD
Package Power Dissipation, PD.................See page 5
Operating Temperature Range
Ambient, TA, Range S ................... –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.
Use the following complete part number when ordering:
Part Number
A3979SLP
Pb-free
–
Ambient, TA (°C)
–20 to 85
A3979SLP-T
Yes
26184.23