A3979 Datasheet

A3979
Microstepping DMOS Driver with Translator
Features and Benefits
Description
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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 (1/16 step)
precision. 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 ±2.5 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.
±2.5 A, 35 V output rating
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
Package: 28 lead TSSOP (suffix LP) with
exposed thermal pad
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 interfaces to program.
The A3979 interface is an ideal fit for applications where a
complex microprocessor is unavailable or is overburdened.
Internal synchronous-rectification control circuitry is provided
to improve power dissipation during PWM operation. Internal
circuit protection includes: thermal shutdown with hysteresis,
UVLO (undervoltage lockout), and crossover-current
protection. Special power-on sequencing is not required.
The A3979 is supplied in a low-profile (height ≤1.20 mm),
28-pin TSSOP with exposed thermal pad. The package is lead
(Pb) free, with 100% matte tin leadframe plating.
Not to scale
Pin-out Diagram
SENSE1 1
28 VBB1
HOME 2
27 SLEEP
DIR 3
26 ENABLE
OUT1A 4
PFD 5
RC1 6
25 OUT1B
AGND 7
REF 8
RC2 9
VDD 10
24 CP2
PWM
Timer
÷8
Translator
and
Control
Logic
Charge
Pump
23 CP1
22 VCP
21 PGND
Reg
20 VREG
19 STEP
OUT2A 11
18 OUT2B
MS2 12
17 RESET
MS1 13
16 SR
SENSE2 14
15 VBB2
AGND and PGND must be
connected together externally
26184.23F
A3979
DMOS Microstepping Driver with Translator
Selection Guide
Part Number
Packing
A3979SLPTR-T
4000 pieces per reel
Absolute Maximum Ratings
Load Supply Voltage
VBB
Output Current
IOUT
Logic Supply Voltage
VDD
Logic Input Voltage Range
Sense Voltage
Reference Voltage
Operating Ambient Temperature
VIN
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.
V
±2.5
A
7.0
V
tW > 30 ns
–0.3 to VDD + 0.3
V
tW < 30 ns
–1 to VDD + 1
V
0.5
V
VSENSE
VREF
TA
35
Range S
VDD
V
–20 to 85
°C
Junction Temperature
TJ(max)
150
°C
Storage Temperature
Tstg
–55 to 150
°C
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
2
A3979
DMOS Microstepping Driver with Translator
Functional Block Diagram
0.22 µF
0.22 µF
CP2
VREG
Logic
Supply
CP1
2V
VDD
UVLO and
Fault
Regulator
Bandgap
Charge
Pump
VCP
Reference
Supply
0.22 µF
Load
Supply
REF
DAC
DMOS Full Bridge
VBB1
RC1
>47 µF
RT1
CT1
OUT1A
4
STEP
OUT1B
DIR
PWM Timer:
PWM Latch
Blanking
Mixed Decay
RESET
MS1
Translator
MS2
SENSE1
RS1
Gate
Drive
HOME
CS1
4
SLEEP
Control
Logic
SR
DMOS Full Bridge
VBB2
ENABLE
OUT2A
VPFD
PFD
0.1 µF
RC2
RT2
OUT2B
PWM Timer:
PWM Latch
Blanking
Mixed Decay
CT2
SENSE2
RS2
DAC
CS2
Exposed Thermal Pad
AGND
PGND
(Required)
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
3
A3979
DMOS Microstepping Driver with Translator
ELECTRICAL CHARACTERISTICS at TA = 25°C, VBB = 35 V, VDD = 3.0 to 5.5 V (unless otherwise noted)
Characteristics
Output Drivers
Symbol
Load Supply Voltage Range
VBB
Output Leakage Current2
IDSS
Output On Resistance
RDS(On)
Body Diode Forward Voltage
VF
Motor Supply Current
IBB
Control Logic
Logic Supply Voltage Range
VDD
Logic Supply Current
IDD
Logic Input Voltage
Logic Input Current2
Reference Input Voltage Range
Reference Input Current
HOME Output Voltage
Mixed Decay Mode Trip Point
Gain (Gm) Error3
STEP Pulse Width
Blank Time
Fixed Off-Time
Crossover Dead Time
Test Conditions
Operating
During Sleep mode
VOUT = VBB
VOUT = 0 V
Source driver, IOUT = –2.5 A
Sink driver, IOUT = 2.5 A
Source diode, IF = –2.5 A
Sink diode, IF = 2.5 A
fPWM < 50 kHz
Operating, outputs disabled
Sleep mode
Operating
fPWM < 50 kHz
Outputs off
Sleep mode
VIN(1)
VIN(0)
Min.
Typ.1
Max.
Units
8
0
–
–
–
–
–
–
–
–
–
–
–
<1.0
<1.0
0.28
0.22
–
–
–
–
–
35
35
20
–20
0.335
0.265
1.4
1.4
8.0
6.0
20
V
V
μA
μA
Ω
Ω
V
V
mA
mA
μA
3.0
–
–
–
5.0
–
–
–
5.5
12
10
20
V
mA
mA
μA
0.7× VDD
–
–
V
0.3 ×VDD
20
μA
–
–
IIN(1)
VIN = 0.7 × VDD
–20
<1.0
IIN(0)
VIN = 0.3 × VDD
–20
<1.0
20
μA
VREF
IREF
Operating
0
–
0.7× VDD
–
0
–
VDD
±3
–
V
μA
V
–
–
0.3× VDD
V
–
0.6 ×VDD
–
V
VHOME(1) IHOME(1) = –200 μA
VHOME(0) IHOME(0) = 200 μA
VPFDH
–
0.21×VDD
–
V
RT = 56 kΩ, CT = 680 pF
–
–
–
1
700
–
–
–
–
950
±10
±5.0
±5.0
–
1200
%
%
%
μs
ns
RT = 56 kΩ, CT = 680 pF
30
38
46
μs
Synchronous rectification enabled
100
475
800
ns
VPFDL
EG
tW
tBLANK
tOFF
tDT
V
VREF = 2 V, Phase Current = 38.27%
VREF = 2 V, Phase Current = 70.71%
VREF = 2 V, Phase Current = 100.00%
Continued on the next page...
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
4
A3979
DMOS Microstepping Driver with Translator
ELECTRICAL CHARACTERISTICS, continued at TA = 25°C, VBB = 35 V, VDD = 3.0 to 5.5 V (unless otherwise noted)
Characteristics
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
UVLO Enable Threshold
UVLO Hysteresis
Symbol
Test Conditions
TJSD
TJSDHYS
VUVLO Increasing VDD
VUVLOHYS
Min.
–
–
2.45
0.05
Typ.1
165
15
2.7
0.10
Max.
–
–
2.95
–
Units
°C
°C
V
V
1Typical data are for initial design estimations only, and assume optimum manufacturing and application conditions. Performance may vary for
individual units, within the specified maximum and minimum limits.
2Negative current is defined as coming out of (sourcing from) the specified device pin.
3E = ( [ V
G
REF / 8] – VSENSE ) / ( VREF / 8 ).
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic
Symbol
Package Thermal Resistance
RθJA
Test Conditions*
Value
Units
Two-layer PCB with 3.8 in.2 of copper area on each side
connected with thermal vias and to device exposed pad
32
ºC/W
High-K PCB (multilayer with significant copper areas,
based on JEDEC standard)
28
ºC/W
*Additional thermal information available on Allegro Web site.
Maximum Power Dissipation, PD(max)
5.0
4.5
Power Dissipation, PD (W)
4.0
H
(R igh-
3.5
θJ
2-
La
3.0
ye
A
K
= PCB
28
ºC
/W
rP
)
(R CB w
ith
θJ
A =
3
32 .8 in 2
ºC co
/W pp
er
)
p
2.5
2.0
er
1.5
sid
e
1.0
0.5
0.0
20
40
60
80
100
120
Temperature (°C)
140
160
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
5
A3979
DMOS Microstepping Driver with Translator
Timing Requirements
(TA = +25°C, VDD = 5 V, Logic Levels are VDD and Ground)
STEP
50%
C
D
B
A
MS1/MS2/
DIR/RESET
E
SLEEP
Dwg. WP-042
A. Minimum Command Active Time
Before Step Pulse (Data Set-Up Time) ..... 200 ns
B. Minimum Command Active Time
After Step Pulse (Data Hold Time) ............ 200 ns
C. Minimum STEP Pulse Width ...................... 1.0 μs
D. Minimum STEP Low Time ......................... 1.0 μs
E. Maximum Wake-Up Time ......................... 1.0 ms
Figure 1. Logic Interface Timing Diagram
Table 1. Microstep Resolution Truth Table
MS1
MS2
Microstep Resolution
Excitation Mode
L
L
Full Step
2 Phase
H
L
Half Step
1-2 Phase
L
H
Quarter Step
W1-2 Phase
H
H
Sixteenth Step
4W1-2 Phase
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
6
A3979
DMOS Microstepping Driver with Translator
Functional Description
Device Operation. The A3979 is a complete micro-
Step Input (STEP). A low-to-high transition on the
stepping motor driver with a built-in translator for easy
operation with minimal control lines. It is designed to
operate bipolar stepper motors in full-, half-, quarter-, and
sixteenth-step modes. The currents in each of the two output
full-bridges (all of the N-channel MOSFETs) are regulated
with fixed off-time PMW (pulse width modulated) control
circuitry. At each step, the current for each full-bridge is
set by the value of its external current-sense resistor (RS1
or RS2), a reference voltage (VREF), and the output voltage
of its DAC (which in turn is controlled by the output of the
translator).
STEP input sequences the translator and advances the motor
one increment. The translator controls the input to the DACs
and the direction of current flow in each winding. The size
of the increment is determined by the combined state of
inputs MS1 and MS2 (see table 1).
At power-on or reset, the translator sets the DACs and the
phase current polarity to the initial Home state (shown in
figures 2 through 5), and the current regulator to Mixed
decay mode for both phases. When a step command signal
occurs on the STEP input, the translator automatically
sequences the DACs to the next level and current polarity.
(See table 2 for the current-level sequence.) The microstep
resolution is set by the combined effect of inputs MS1 and
MS2, as shown in table 1.
While stepping is occurring, if the next output level of the
DACs is lower than the immediately preceeding output
level, then the decay mode (Fast, Slow, or Mixed) for the
active full bridge is set by the PFD input. If the next DAC
output level is higher than or equal to the preceeding level,
then the decay mode for that full bridge will be Slow decay.
This automatic current-decay selection improves microstepping performance by reducing the distortion of the current
waveform due to back EMF of the motor.
RESET Input ( R̄¯Ē¯S̄¯Ē¯T̄
¯ ). The R̄¯Ē¯S̄¯Ē¯T̄¯ input (active
low) sets the translator to a predefined Home state (shown
in figures 2 through 5), and turns off all of the DMOS outputs. The HOME output goes low and all STEP inputs are
ignored until the R̄¯Ē
¯S̄¯Ē
¯T̄
¯ input is set to high.
Home Output (HOME). The HOME output is a logic
output indicator of the initial state of the translator. At
power-on, the translator is reset to the Home state (shown in
figures 2 through 5).
Microstep Select (MS1 and MS2). The input on
terminals MS1 and MS2 selects the microstepping format,
as shown in table 1. Any changes made to these inputs do not
take effect until the next rising edge of a step command signal
on the STEP input.
Direction Input (DIR). The state of the DIR input determines the direction of rotation of the motor. Any changes
made to this input does not take effect until the next rising
edge of a step command signal on the STEP input.
Internal PWM Current Control. Each full bridge is
controlled by a fixed–off-time PWM current-control circuit
that limits the load current to a desired value, ITRIP . Initially,
a diagonal pair of source and sink MOS outputs are enabled
and current flows through the motor winding and the current
sense resistor, RSx. When the voltage across RSx equals the
DAC output voltage, the current-sense comparator resets the
PWM latch. The latch then turns off either the source MOSFETs (when in Slow decay mode) or the sink and source
MOSFETs (when in Fast or Mixed decay mode).
The maximum value of current limiting is set by the selection of RS and the voltage at the VREF input with a transconductance function approximated by:
ITRIPmax = VREF/8RS
The DAC output reduces the VREF output to the current-sense comparator in precise steps (see table 2 for
% ITRIPmax at each step).
ITRIP = (% ITRIPmax/100) ITRIPmax
It is critical that the maximum rating (0.5 V) on either the
SENSE1 and SENSE2 pins is not exceeded. For full stepping, VREF can be applied up to the maximum rating of VDD
because the peak sense value is 0.707 × VREF / 8. In all other
modes, VREF should not exceed 4 V.
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
7
A3979
DMOS Microstepping Driver with Translator
Fixed Off-Time. The internal PWM current-control circuitry uses a one-shot timer to control the duration of time
that the MOSFETs remain off. The one shot off-time, tOFF,
is determined by the selection of external resistors, RTx , and
capacitors, CTx , connected from each RCx timing terminal to
ground. The off-time, over a range of values of CT = 470 pF
to 1500 pF and RT = 12 kΩ to 100 kΩ is approximated by:
tOFF = RTCT
RC Blanking. In addition to the fixed off-time of the
PWM control circuit, the CTx component sets the comparator blanking time. This function blanks the output of the
current-sense comparators when the outputs are switched
by the internal current-control circuitry. The comparator
outputs are blanked to prevent false overcurrent detection
due to reverse recovery currents of the clamp diodes, or to
switching transients related to the capacitance of the load.
The blank time tBLANK can be approximated by:
tBLANK = 1400CT
Charge Pump (CP1 and CP2). The charge pump is
used to generate a gate supply greater than that of VBB for
driving the source-side DMOS gates. A 0.22 μF ceramic
capacitor should be connected between CP1 and CP2 for
pumping purposes. In addition, a 0.22 μF ceramic capacitor
is required between VCP and VBB, to act as a reservoir for
operating the high-side DMOS gates.
VREG (VREG). This internally-generated voltage is used to
operate the sink-side DMOS outputs. The VREG pin must
be decoupled with a 0.22 μF capacitor to ground. VREG is
internally monitored, and in the case of a fault condition, the
DMOS outputs of the device are disabled.
Enable Input ( Ē¯N̄¯Ā¯B̄¯L̄
¯Ē¯ ). This active-low input
enables all of the DMOS outputs. When set to a logic high,
the outputs are disabled. The inputs to the translator (STEP,
DIR, MS1, and MS2), all remain active, independent of the
Ē
¯N̄¯Ā¯B̄
¯L̄
¯Ē
¯ input state.
Shutdown. During normal operation, in the event of a
fault, such as overtemperature (excess TJ) or an undervolt-
age on VCP, the outputs of the device are disabled until the
fault condition is removed.
At power up, and in the event of low VDD, the undervoltage
lockout (UVLO) circuit disables the drivers and resets the
translator to the Home state.
Sleep Mode ( S̄¯L̄
¯Ē¯Ē¯P̄¯ ). This active-low control input
is used to minimize power consumption when the motor is
not in use. It disables much of the internal circuitry including the output DMOS FETs, current regulator, and charge
pump. Setting this to a logic high allows normal operation,
as well as start-up (at which time the A3979 drives the
motor to the Home microstep position). When bringing the
device out of Sleep mode, in order to allow the charge pump
(gate drive) to stabilize, provide a delay of 1 ms before issuing a step command signal on the STEP input.
Percent Fast Decay Input (PFD). When a STEP
input signal commands a lower output current than the
previous step, it switches the output current decay to either
Slow, Fast, or Mixed decay mode, depending on the voltage
level at the PFD input. If the voltage at the PFD input is
greater than 0.6 × VDD , then Slow decay mode is selected.
If the voltage on the PFD input is less than 0.21 × VDD , then
Fast decay mode is selected. Mixed decay mode is selected
when VPFD is between these two levels, as described in
the next section. This terminal should be decoupled with a
0.1 μF capacitor.
Mixed Decay Operation. If the voltage on the PFD input
is between 0.6 × VDD and 0.21 × VDD , the bridge operates
in Mixed decay mode, as determined by the step sequence
(shown in figures 2 through 5). As the trip point is reached,
the device goes into Fast decay mode until the voltage
on the RCx terminal decays to the same level as voltage
applied to the PFD terminal. The time that the device operates in fast decay is approximated by:
tFD = RTCTln (0.6VDD/VPFD)
After this Fast decay portion, the device switches to Slow
decay mode for the remainder of the fixed off-time period.
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
8
A3979
DMOS Microstepping Driver with Translator
Synchronous Rectification. When a PWM offcycle is triggered by an internal fixed–off-time cycle, load
current recirculates according to the decay mode selected
by the control logic. The A3979 synchronous rectification
feature turns on the appropriate MOSFETs during the decay
of the current, and effectively shorts out the body diodes
with the low RDS(On) driver. This reduces power dissipation
significantly and eliminates the need for external Schottky
diodes for most applications. The synchronous rectification
can be set to either Active mode or Disabled mode:
• Active Mode. When the SR input is logic low, Active
mode is enabled and synchronous rectification can occur.
This mode prevents reversal of the load current by turning
off synchronous rectification when a zero current level is
detected. This prevents the motor winding from conducting in the reverse direction.
• Disabled Mode. When the SR input is logic high, synchronous rectification is disabled. This mode is typically used when external diodes are required to transfer
power dissipation from the A3979 package to the external
diodes.
Applications Information
Layout. The printed circuit board on which the device is
Current Sensing. To minimize inaccuracies caused by
mounted should have a heavy ground plane. For optimum
electrical and thermal performance, the A3979 should be
soldered directly onto the board.
ground-trace IR drops in sensing the output current level,
the current-sense resistors, RSx, should have an independent
ground return to the star ground of the device. This path
should be as short as possible.
The load supply terminals, VBBx, should be decoupled with
an electrolytic capacitor (>47 μF is recommended), placed
as close to the device as possible.
To avoid problems due to capacitive coupling of the high
dv / dt switching transients, route the bridge-output traces
away from the sensitive logic-input traces.
Always drive the logic inputs with a low source impedance
to increase noise immunity.
Grounding. The AGND (analog ground) terminal and the
PGND (power ground) terminal must be connected together
externally.
All ground lines should be connected together and be as
short as possible. A star ground system, centered under the
device, is an optimum design.
The copper ground plane located under the exposed thermal
pad is typically used as the star ground.
For low-value sense resistors, the IR drops in the printed circuit board sense resistor traces can be significant and should
be taken into account.
The use of sockets should be avoided as they can introduce
variation in RSx due to their contact resistance.
Allegro MicroSystems recommends a value of RS given by
RS = 0.5/ITRIPmax
Thermal Protection. This internal circuitry turns off
all drivers when the junction temperature reaches 165°C,
typical. It is intended only to protect the device from failures
due to excessive junction temperatures and should not imply
that output short circuits are permitted. Thermal shutdown
has a hysteresis of approximately 15°C.
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
9
A3979
DMOS Microstepping Driver with Translator
STEP Input
STEP Input
HOME Output
HOME Output
100.00
100.00
70.71
70.71
Slow
Phase 1
IOUT1A
Direction = H
(%)
–100.00
100.00
–70.71
–100.00
100.00
70.71
Phase 2
IOUT2A
Direction = H
(%)
0.00
Slow
Slow Slow
Mixed
Mixed
Slow
Slow
Mixed
0.00
–70.71
–70.71
–100.00
–100.00
Figure 2. Decay Mode for Full-Step Increments
Mixed
0.00
70.71
Phase 2
IOUT2A
Direction = H
(%)
Slow
Mixed
Home Microstep Position
–70.71
Home Microstep Position
0.00
Slow
Mixed
Home Microstep Position
Slow
Home Microstep Position
Phase 1
IOUT1A
Direction = H
(%)
Figure 3. Decay Modes for Half-Step Increments
STEP Input
HOME Output
100.00
92.39
70.71
38.27
Slow
Mixed
Slow
Mixed
Slow
0.00
Home Microstep Position
Phase 1
IOUT1A
Direction = H
(%)
–38.27
–70.71
–92.39
–100.00
100.00
92.39
70.71
Phase 2
IOUT2A
Direction = H
(%)
38.27
Slow
Mixed
Slow
Mixed
Slow
Mixed
0.00
–38.27
–70.71
–92.39
–100.00
Figure 4. Decay Modes for Quarter-Step Increments
10
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3979
DMOS Microstepping Driver with Translator
STEP Input
HOME Output
100.00
95.69
88.19
83.15
77.30
70.71
63.44
55.56
47.14
38.27
29.03
19.51
Phase 1
IOUT1A
Direction = H
(%)
9.8
Slow
0.00
Mixed
Slow
Mixed
–9.8
–19.51
–29.03
Home Microstep Position
–38.27
–47.14
–55.56
–63.44
–70.71
–77.30
–83.15
–88.19
–95.69
–100.00
100.00
95.69
88.19
83.15
77.30
70.71
63.44
55.56
47.14
38.27
29.03
19.51
Phase 2
IOUT2A
Direction = H
(%)
9.8
0.00
Slow
Mixed
Slow
Mixed
Slow
–9.8
–19.51
–29.03
–38.27
–47.14
–55.56
–63.44
–70.71
–77.30
–83.15
–88.19
–95.69
–100.00
Figure 5. Decay Modes for Sixteenth-Step Increments
11
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3979
DMOS Microstepping Driver with Translator
Table 2. Step Sequencing Settings
Home microstep position at Step Angle 45º; DIR = H; 360° = 4 full steps
Full
Step
#
Half
Step
#
1
1/4
Step
#
1
2
1
2
3
4
3
5
6
2
4
7
8
Phase 1
Current
Phase 2
Current
[% ItripMax]
[% ItripMax]
(%)
100.00
(%)
0.00
Step
Angle
(º)
0.0
2
99.52
9.80
5.6
3
98.08
19.51
11.3
35
–98.08
–19.51
191.3
4
95.69
29.03
16.9
36
–95.69
–29.03
196.9
5
92.39
38.27
22.5
37
–92.39
–38.27
202.5
6
88.19
47.14
28.1
38
–88.19
–47.14
208.1
7
83.15
55.56
33.8
39
–83.15
–55.56
213.8
1/16
Step
#
1
8
77.30
63.44
39.4
9
70.71
70.71
45.0
10
63.44
77.30
Full
Step
#
Half
Step
#
5
1/4
Step
#
9
1/16
Step
#
33
34
10
Phase 1
Current
Phase 2
Current
[% ItripMax]
[% ItripMax]
Step
Angle
–100.00
(%)
0.00
180.0
–99.52
–9.80
185.6
(%)
(º)
40
–77.30
–63.44
219.4
41
–70.71
–70.71
225.0
50.6
42
–63.44
–77.30
230.6
3
6
11
11
55.56
83.15
56.3
43
–55.56
–83.15
236.3
12
47.14
88.19
61.9
44
–47.14
–88.19
241.9
13
38.27
92.39
67.5
45
–38.27
–92.39
247.5
14
29.03
95.69
73.1
46
–29.03
–95.69
253.1
15
19.51
98.08
78.8
47
–19.51
–98.08
258.8
16
9.80
99.52
84.4
17
0.00
100.00
90.0
18
–9.80
99.52
19
–19.51
20
–29.03
21
22
23
12
48
–9.80
–99.52
264.4
49
0.00
–100.00
270.0
95.6
50
9.80
–99.52
275.6
98.08
101.3
51
19.51
–98.08
281.3
95.69
106.9
52
29.03
–95.69
286.9
–38.27
92.39
112.5
53
38.27
–92.39
292.5
–47.14
88.19
118.1
54
47.14
–88.19
298.1
–55.56
83.15
123.8
55
55.56
–83.15
303.8
24
–63.44
77.30
129.4
25
–70.71
70.71
135.0
26
–77.30
63.44
27
–83.15
28
–88.19
29
30
7
13
14
56
63.44
–77.30
309.4
57
70.71
–70.71
315.0
140.6
58
77.30
–63.44
320.6
55.56
146.3
59
83.15
–55.56
326.3
47.14
151.9
60
88.19
–47.14
331.9
–92.39
38.27
157.5
61
92.39
–38.27
337.5
–95.69
29.03
163.1
62
95.69
–29.03
343.1
31
–98.08
19.51
168.8
63
98.08
–19.51
348.8
32
–99.52
9.80
174.4
64
99.52
–9.80
354.4
4
8
15
16
12
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3979
DMOS Microstepping Driver with Translator
Terminal List Table
Number
Name
1
SENSE1
2
HOME
Description
Sense resistor for Bridge 1
Logic Output
3
DIR
4
OUT1A
Logic input
Output A for Bridge 1
5
PFD
Mixed decay setting
6
RC1
Analog input for fixed off-time for Bridge 1
7
AGND
8
REF
Current trip reference voltage input
Analog Ground
9
RC2
Analog input for fixed off-time for Bridge 2
10
VDD
Logic supply
11
OUT2A
12
MS2
Logic input
13
MS1
Logic input
14
SENSE2
15
VBB2
16
SR
Logic input
17
R̄¯Ē¯S̄¯Ē¯T̄
¯
Logic input
18
OUT2B
Output B for Bridge 2
19
STEP
Output A for Bridge 2
Sense resistor for Bridge 2
Load supply for Bridge 2
Logic input
20
VREG
Regulator decoupling
21
PGND
Power Ground
22
VCP
Reservoir capacitor
23
CP1
Charge pump capacitor 1
24
CP2
Charge pump capacitor 2
25
1OUT1B
Output B for Bridge 1
26
Ē¯N̄¯Ā¯B̄¯L̄¯Ē¯
Logic input
27
S̄¯L̄¯Ē¯Ē¯P̄¯
Logic input
28
VBB1
Load supply for Bridge 1
13
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3979
DMOS Microstepping Driver with Translator
LP Package, 28-pin TSSOP
0.45
9.70 ±0.10
28
+0.05
0.15 –0.06
0.65
28
4° ±4
1.65
B
3.00
4.40 ±0.10
6.40 ±0.20
3.00
6.10
0.60 ±0.15
A
1
(1.00)
2
5.00
0.25
28X
SEATING
PLANE
0.10 C
+0.05
0.25 –0.06
0.65
C
SEATING PLANE
GAUGE PLANE
1 2
5.00
C
PCB Layout Reference View
1.20 MAX
0.10 MAX
For reference only
(reference JEDEC MO-153 AET)
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
A Terminal #1 mark area
B Exposed thermal pad (bottom surface)
C Reference land pattern layout (reference IPC7351 SOP65P640X120-29CM);
All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary
to meet application process requirements and PCB layout tolerances; when
mounting on a multilayer PCB, thermal vias at the exposed thermal pad land
can improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5)
14
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3979
DMOS Microstepping Driver with Translator
Revision History
Revision
Revision Date
Rev. F
June 21, 2013
Description of Revision
Update decay charts
Copyright ©2005-2013, Allegro MicroSystems, LLC
Allegro MicroSystems, LLC reserves the right to make, from time to time, such departures from the detail specifications as may be required to
permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that
the information being relied upon is current.
Allegro’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the
failure of that life support device or system, or to affect the safety or effectiveness of that device or system.
The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, LLC assumes no responsibility for its
use; nor for any infringement of patents or other rights of third parties which may result from its use.
For the latest version of this document, visit our website:
www.allegromicro.com
15
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
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