A4985 Datasheet

A4985
DMOS Microstepping Driver with Translator
And Overcurrent Protection
Features and Benefits
▪
▪
▪
▪
▪
▪
▪
▪
▪
▪
▪
▪
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Low RDS(ON) outputs
Automatic current decay mode detection/selection
Mixed and Slow current decay modes
Synchronous rectification for low power dissipation
Internal UVLO
Crossover-current protection
3.3 and 5 V compatible logic supply
Thin profile QFN and TSSOP packages
Thermal shutdown circuitry
Short-to-ground protection
Shorted load protection
Low current Sleep mode, < 10 µA
No smoke no fire (NSNF) compliance (ET package)
Packages:
Description
The A4985 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 eighth-step
modes. Step modes are selectable by MSx logic inputs. It has
an output drive capacity of up to 35 V and ±1 A. The A4985
includes a fixed off-time current regulator which has the ability
to operate in Slow or Mixed decay modes.
The ET package meets customer requirements for no smoke
no fire (NSNF) designs by adding no-connect pins between
critical output, sense, and supply pins. So, in the case of a
pin-to-adjacent-pin short, the device does not cause smoke
or fire. Additionally, the device does not cause smoke or fire
when any pin is shorted to ground or left open.
The translator is the key to the easy implementation of the
A4985. 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 A4985 interface is an ideal fit for applications where a
complex microprocessor is unavailable or is overburdened.
24-contact QFN
with exposed thermal pad
4 mm × 4 mm × 0.75 mm
(ES package)
During stepping operation, the chopping control in the A4985
automatically selects the current decay mode, Slow or Mixed.
In Mixed decay mode, the device is set initially to a fast decay
for a proportion of the fixed off-time, then to a slow decay for
the remainder of the off-time. Mixed decay current control
results in reduced audible motor noise, increased step accuracy,
and reduced power dissipation.
32-contact QFN
with exposed thermal pad
5 mm × 5 mm × 0.90 mm
(ET package)
24-pin TSSOP
with exposed thermal pad
(LP Package)
Continued on the next page…
Typical Application Diagram
VDD
0.1 µF
VREG ROSC
0.22 µF
0.1 µF
0.22 µF
CP1
CP2
VCP
VDD
VBB2
5 kΩ
Microcontroller or
Controller Logic
SLEEP
STEP
VBB1
OUT1A
A4985
OUT1B
SENSE1
MS1
MS2
DIR
OUT2A
ENABLE
OUT2B
RESET
SENSE2
VREF
GND
4985-DS, Rev. 5
GND
100 µF
DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
Description (continued)
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 A4985 is supplied in three surface mount packages: two QFN
packages, the 4 mm × 4 mm, 0.75 mm nominal overall height ES
package, and the 5 mm × 5 mm × 0.90 mm ET package. The LP
package is a 24-pin TSSOP. All three packages have exposed pads
for enhanced thermal dissipation, and are lead (Pb) free (suffix –T),
with 100% matte tin plated leadframes.
Selection Guide
Part Number
Package
Packing
A4985SESTR-T
24-contact QFN with exposed thermal pad
1500 pieces per 7-in. reel
A4985SETTR-T
32-contact QFN with exposed thermal pad
1500 pieces per 7-in. reel
A4985SLPTR-T
24-pin TSSOP with exposed thermal pad
4000 pieces per 13-in. reel
Absolute Maximum Ratings
Characteristic
Symbol
Notes
Rating
Units
35
V
Load Supply Voltage
VBB
Output Current
IOUT
±1
A
Logic Input Voltage
VIN
–0.3 to 5.5
V
Logic Supply Voltage
VDD
–0.3 to 5.5
V
–2.0 to 37
V
VSENSE
–0.5 to 0.5
V
VREF
5.5
V
Motor Outputs Voltage
Sense Voltage
Reference Voltage
Operating Ambient Temperature
Maximum Junction
Storage Temperature
–20 to 85
ºC
TJ(max)
TA
Range S
150
ºC
Tstg
–55 to 150
ºC
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
2
DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
Functional Block Diagram
0.1 µF
0.22 µF
VREG
VDD
Current
Regulator
ROSC
CP1
CP2
Charge
Pump
OSC
VCP
0.1 µF
DMOS Full Bridge
REF
DAC
VBB1
OUT1A
OUT1B
PWM Latch
Blanking
Mixed Decay
STEP
Gate
Drive
DIR
RESET
OCP
Translator
MS1
Control
Logic
PWM Latch
Blanking
Mixed Decay
ENABLE
SLEEP
DAC
DMOS Full Bridge
VBB2
RS1
OUT2A
OCP
MS2
SENSE1
OUT2B
SENSE2
RS2
VREF
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
3
A4985
DMOS Microstepping Driver with Translator
And Overcurrent Protection
ELECTRICAL CHARACTERISTICS1 at TA = 25°C, VBB = 35 V (unless otherwise noted)
Characteristics
Output Drivers
Min.
Typ.2
Max.
Units
8
0
3.0
–
–
–
–
–
–
–
–
–
–
–
–
–
700
700
–
–
–
–
–
–
–
–
35
35
5.5
900
900
1.3
1.3
4
2
10
8
5
10
V
V
V
mΩ
mΩ
V
V
mA
mA
μA
mA
mA
μA
VIN(1)
VDD×0.7
–
–
V
VIN(0)
–
–
V
–20
<1.0
VDD×0.3
20
µA
–20
<1.0
20
µA
–
–
5
0.7
20
23
0
–3
–
–
–
100
100
50
11
1
30
30
–
0
–
–
–
475
–
–
19
1.3
40
37
4
3
±15
±5
±5
800
kΩ
kΩ
%
μs
μs
μs
V
μA
%
%
%
ns
1.1
–
–
2.7
–
–
165
15
2.8
90
–
–
–
2.9
–
A
°C
°C
V
mV
Symbol
Load Supply Voltage Range
VBB
Logic Supply Voltage Range
VDD
Output On Resistance
RDS(ON)
Body Diode Forward Voltage
VF
Motor Supply Current
IBB
Logic Supply Current
IDD
Test Conditions
Operating
During Sleep Mode
Operating
Source Driver, IOUT = –800 mA
Sink Driver, IOUT = 800 mA
Source Diode, IF = –800 mA
Sink Diode, IF = 800 mA
fPWM < 50 kHz
Operating, outputs disabled
Sleep Mode
fPWM < 50 kHz
Outputs off
Sleep Mode
Control Logic
Logic Input Voltage
Logic Input Current
Microstep Select
Logic Input Hysteresis
Blank Time
IIN(1)
IIN(0)
RMS1
RMS2
VHYS(IN)
tBLANK
Fixed Off-Time
tOFF
Reference Input Voltage Range
Reference Input Current
VREF
IREF
Current Trip-Level Error3
errI
Crossover Dead Time
Protection
Overcurrent Protection Threshold4
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
VDD Undervoltage Lockout
VDD Undervoltage Hysteresis
tDT
IOCPST
TTSD
TTSDHYS
VDDUVLO
VDDUVLOHYS
VIN = VDD×0.7
VIN = VDD×0.3
As a % of VDD
OSC = VDD or GND
ROSC = 25 kΩ
VREF = 2 V, %ITripMAX = 38.27%
VREF = 2 V, %ITripMAX = 70.71%
VREF = 2 V, %ITripMAX = 100.00%
VDD rising
1For
input and output current specifications, negative current is defined as coming out of (sourcing) the specified device pin.
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.
3V
ERR = [(VREF/8) – VSENSE] / (VREF/8).
4Overcurrent protection (OCP) is tested at T = 25°C in a restricted range and guaranteed by characterization.
A
2Typical
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
4
DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
THERMAL CHARACTERISTICS may require derating at maximum conditions
Characteristic
Symbol
Test Conditions*
RθJA
Package Thermal Resistance
Value Units
ES package; estimated, on 4-layer PCB, based on JEDEC standard
37
ºC/W
ET package; estimated, on 4-layer PCB, based on JEDEC standard
32
ºC/W
LP package; on 4-layer PCB, based on JEDEC standard
28
ºC/W
*In still air. Additional thermal information available on Allegro Web site.
Maximum Power Dissipation, PD(max)
5.5
5.0
4.5
Power Dissipation, PD (W)
4.0
R
θJ
3.5
A
=
32
ºC
3.0
R
R
2.5
θJ
2.0
θJ
/W
A
=3
A
7º
=
C/
28
ºC
/W
W
1.5
1.0
0.5
0.0
20
40
60
80
100
120
Temperature (°C)
140
160
180
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
5
DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
tA
tB
STEP
tC
tD
MS1, MS2,
RESET, or DIR
Time Duration
Symbol
Typ.
Unit
STEP minimum, HIGH pulse width
tA
1
μs
STEP minimum, LOW pulse width
tB
1
μs
Setup time, input change to STEP
tC
200
ns
Hold time, input change to STEP
tD
200
ns
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
Eighth Step
2W1-2 Phase
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115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
6
A4985
DMOS Microstepping Driver with Translator
And Overcurrent Protection
Functional Description
Device Operation. The A4985 is a complete microstepping
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 eighth-step resolution modes.
The currents in each of the two output full-bridges and all of the
N-channel DMOS FETs are regulated with fixed off-time PWM
(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 and RS2), a reference voltage (VREF), and the output
voltage of its DAC (which in turn is controlled by the output of
the translator).
At power-on or reset, the translator sets the DACs and the phase
current polarity to the initial Home state (shown in Figures 10
through 13), 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 the MS1 and MS2 inputs, as shown in Table 1.
When stepping, if the new output levels of the DACs are lower
than their previous output levels, then the decay mode for the
active full-bridge is set to Mixed. If the new output levels of the
DACs are higher than or equal to their previous levels, then the
decay mode for the active full-bridge is set to Slow. This automatic current decay selection improves microstepping performance by reducing the distortion of the current waveform that
results from the back EMF of the motor.
Microstep Select (MS1 and MS2). The microstep resolu-
Slow decay mode for the remainder of tOFF. A timing diagram for
this feature appears in Figure 7.
Typically, mixed decay is only necessary when the current in the
winding is going from a higher value to a lower value as determined
by the translator setting. For most loads automatically-selected mixed
decay is convenient because it minimizes ripple when the current is
rising and prevents missed steps when the current is falling. For some
applications where microstepping at very low speeds is necessary,
the lack of back EMF in the winding causes the current to increase in
the load quickly, resulting in missed steps. This is shown in Figure 2.
By pulling the ROSC pin to ground, mixed decay is set to be active
100% of the time, for both rising and falling currents, and prevents
missed steps as shown in Figure 3. If this is not an issue, it is recommended that automatically-selected mixed decay be used, because
it will produce reduced ripple currents. Refer to the Fixed Off-Time
section for details.
Low Current Microstepping. Intended for applications
where the minimum on-time prevents the output current from
regulating to the programmed current level at low current steps.
To prevent this, the device can be set to operate in Mixed decay
mode on both rising and falling portions of the current waveform.
This feature is implemented by shorting the ROSC pin to ground.
In this state, the off-time is internally set to 30 µs.
¯ S̄
¯ Ē
¯ T̄
¯ ). The R̄¯ Ē¯ S̄¯ Ē¯ T̄¯ input sets the translator
Reset Input ( R̄¯ Ē
to a predefined Home state (shown in Figures 10 through 13), and
turns off all of the FET outputs. All STEP inputs are ignored until
¯ Ē
¯ S̄¯ Ē
¯ T̄
¯ input is set to high.
the R̄
tion is set by the voltage on logic inputs MS1 and MS2, as shown
in Table 1. MS1 has a 100 kΩ pull-down resistance, and MS2 has Step Input (STEP). A low-to-high transition on the STEP
input sequences the translator and advances the motor one increa 50 kΩ pull-down resistance. When changing the step mode the
ment. The translator controls the input to the DACs and the direcchange does not take effect until the next STEP rising edge.
tion of current flow in each winding. The size of the increment is
If the step mode is changed without a translator reset, and absodetermined by the combined state of the MS1and MS2 inputs.
lute position must be maintained, it is important to change the
step mode at a step position that is common to both step modes in Direction Input (DIR). This determines the direction of rotation of the motor. Changes to this input do not take effect until the
order to avoid missing steps. When the device is powered down,
or reset due to TSD or an over current event the translator is set to next STEP rising edge.
the home position which is by default common to all step modes. Internal PWM Current Control. Each full-bridge is con-
Mixed Decay Operation. The bridge operates in Mixed
decay mode, at power-on and reset, and during normal running
according to the ROSC configuration and the step sequence, as
shown in Figures 10 through 13. During Mixed decay, when the
trip point is reached, the A4985 initially goes into a fast decay
mode for 31.25% of the off-time, tOFF . After that, it switches to
trolled 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 FET 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
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
7
DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
Slow
Decay
Mixed
Decay
Slow
Decay
Mixed
Decay
Slow
Decay
Mixed
Decay
Slow
Decay
Mixed
Decay
Missed
Step
Voltage on ROSC terminal 2 V/div.
Step input 10 V/div.
t → , 1 s/div.
Figure 2: Missed Steps in Low-Speed Microstepping
Mixed Decay
ILOAD 500 mA/div.
Step input 10 V/div.
No Missed
Steps
t → , 1 s/div.
Figure 3: Continuous Stepping Using Automatically-Selected Mixed Stepping (ROSC pin grounded)
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115 Northeast Cutoff, Box 15036
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8
DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
turns off either the source FET (when in Slow Decay Mode) or
the sink and source FETs (when in Mixed Decay Mode).
The maximum value of current limiting is set by the selection of
RSx and the voltage at the VREF pin. The transconductance function is approximated by the maximum value of current limiting,
ITripMAX (A), which is set by
× RS)
ITripMAX = VREF / ( 8 where RS is the resistance of the sense resistor (Ω) and VREF is
the input voltage on the REF pin (V).
The DAC output reduces the VREF output to the current sense
comparator in precise steps, such that
Itrip = (%ITripMAX / 100)
× ITripMAX
(See Table 2 for %ITripMAX at each step.)
It is critical that the maximum rating (0.5 V) on the SENSE1 and
SENSE2 pins is not exceeded.
Fixed Off-Time. The internal PWM current control circuitry
uses a one-shot circuit to control the duration of time that the
DMOS FETs remain off. The off-time, tOFF, is determined by the
ROSC terminal. The ROSC terminal has three settings:
▪ ROSC tied to VDD — off-time internally set to 30 µs, decay
mode is automatic Mixed decay except when in full step where
decay mode is set to Slow decay
▪ ROSC tied directly to ground — off-time internally set to
30 µs, current decay is set to Mixed decay for both increasing
and decreasing currents for all step modes.
▪ ROSC through a resistor to ground — off-time is determined
by the following formula, the decay mode is automatic Mixed
decay for all step modes except full step which is set to slow
decay.
tOFF ≈ ROSC ⁄ 825
where tOFF is in µs.
Blanking. 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, and switching transients related to the capacitance
of the load. The blank time, tBLANK (µs), is approximately
Shorted-Load and Short-to-Ground Protection.
If the motor leads are shorted together, or if one of the leads is
shorted to ground, the driver will protect itself by sensing the
overcurrent event and disabling the driver that is shorted, protecting the device from damage. In the case of a short-to-ground, the
¯ Ē
¯
¯ P̄¯ input goes
device will remain disabled (latched) until the S̄ L̄
Ē
high or VDD power is removed. A short-to-ground overcurrent
event is shown in Figure 4.
When the two outputs are shorted together, the current path is
through the sense resistor. After the blanking time (≈1 µs) expires,
the sense resistor voltage is exceeding its trip value, due to the
overcurrent condition that exists. This causes the driver to go into
a fixed off-time cycle. After the fixed off-time expires the driver
turns on again and the process repeats. In this condition the driver
is completely protected against overcurrent events, but the short
is repetitive with a period equal to the fixed off-time of the driver.
This condition is shown in Figure 5.
If the driver is operating in Mixed decay mode, it is normal for
the positive current to spike, due to the bridge going in the forward direction and then in the negative direction, as a result of the
direction change implemented by the Mixed decay feature. This
is shown in Figure 6. In both instances the overcurrent circuitry is
protecting the driver and prevents damage to the device.
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 FET gates. A 0.1 µF ceramic capacitor, should be
connected between CP1 and CP2. In addition, a 0.1 µF ceramic
capacitor is required between VCP and VBB, to act as a reservoir
for operating the high-side FET gates.
Capacitor values should be Class 2 dielectric ±15% maximum,
or tolerance R, according to EIA (Electronic Industries Alliance)
specifications.
VREG (VREG). This internally-generated voltage is used to
operate the sink-side FET outputs. The nominal output voltage
of the VREG terminal is 7 V. The VREG pin must be decoupled
with a 0.22 µF ceramic capacitor to ground. VREG is internally
monitored. In the case of a fault condition, the FET outputs of the
A4985 are disabled.
Capacitor values should be Class 2 dielectric ±15% maximum,
or tolerance R, according to EIA (Electronic Industries Alliance)
specifications.
tBLANK ≈ 1 µs
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115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
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9
A4985
DMOS Microstepping Driver with Translator
And Overcurrent Protection
Enable Input ( Ē¯ N̄¯ Ā¯ B̄¯ L̄¯ Ē¯ ). This input turns on or off all of the
FET outputs. When set to a logic high, the outputs are disabled.
When set to a logic low, the internal control enables the outputs as
required. The translator inputs STEP, DIR, MS1, and MS2, as well
as the internal sequencing logic, all remain active, independent of
¯ N̄¯ Ā¯ B̄
¯ L̄
¯ Ē
¯ input state.
the Ē
5 A / div.
Fault latched
Shutdown. In the event of a fault, overtemperature (excess TJ)
or an undervoltage (on VCP), the FET outputs of the A4985 are
disabled until the fault condition is removed. At power-on, the
UVLO (undervoltage lockout) circuit disables the FET outputs
and resets the translator to the Home state.
Sleep Mode ( S̄¯ L̄¯ Ē¯ Ē¯ P̄¯ ). To minimize power consumption
when the motor is not in use, this input disables much of the
internal circuitry including the output FETs, current regulator,
¯ Ē
¯ Ē
¯ P̄¯ pin puts the A4985
and charge pump. A logic low on the S̄ L̄
into Sleep mode. A logic high allows normal operation, as well as
start-up (at which time the A4985 drives the motor to the Home
microstep position). When emerging from Sleep mode, in order
to allow the charge pump to stabilize, provide a delay of 1 ms
before issuing a Step command.
t→
Figure 4: Short-to-Ground Event
5 A / div.
Fixed off-time
Mixed Decay Operation. The bridge operates in Mixed
Decay mode, depending on the step sequence, as shown in
Figures 10 through 13. As the trip point is reached, the A4985
initially goes into a fast decay mode for 31.25% of the off-time.
tOFF. After that, it switches to Slow Decay mode for the remainder of tOFF. A timing dagram for this feature appears on the next
page.
Synchronous Rectification. When a PWM-off cycle is
triggered by an internal fixed-off-time cycle, load current recirculates according to the decay mode selected by the control logic.
This synchronous rectification feature turns on the appropriate
FETs during current decay, and effectively shorts out the body
diodes with the low FET RDS(ON). This reduces power dissipation
significantly, and can eliminate the need for external Schottky
diodes in many applications. Synchronous rectification turns off
when the load current approaches zero (0 A), preventing reversal
of the load current.
t→
Figure 5. Shorted Load (OUTxA → OUTxB) in
Slow Decay Mode
5 A / div.
Fixed off-time
Fast decay portion
(direction change)
t→
Figure 6: Shorted Load (OUTxA → OUTxB) in Mixed Decay Mode
10
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
VSTEP
100.00
70.71
See Enlargement A
IOUT
0
–70.71
–100.00
Enlargement A
toff
IPEAK
tFD
tSD
Slow Decay
Mixed Decay
IOUT
Fa
st
De
ca
y
t
Symbol
toff
IPEAK
Characteristic
Device fixed off-time
Maximum output current
tSD
Slow decay interval
tFD
Fast decay interval
IOUT
Device output current
Figure 7: Current Decay Modes Timing Chart
11
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
Application Layout
Layout. The printed circuit board should use a heavy groundplane. For optimum electrical and thermal performance, the
A4985 must be soldered directly onto the board. On the underside of the A4985 package is an exposed pad, which provides a
path for enhanced thermal dissipation. The thermal pad should be
soldered directly to an exposed surface on the PCB. Thermal vias
are used to transfer heat to other layers of the PCB.
In order to minimize the effects of ground bounce and offset
issues, it is important to have a low impedance single-point
ground, known as a star ground, located very close to the device.
By making the connection between the pad and the ground plane
directly under the A4985, that area becomes an ideal location for
a star ground point. A low impedance ground will prevent ground
bounce during high current operation and ensure that the supply
voltage remains stable at the input terminal.
The two input capacitors should be placed in parallel, and as
close to the device supply pins as possible. The ceramic capacitor (CIN1) should be closer to the pins than the bulk capacitor
(CIN2). This is necessary because the ceramic capacitor will be
responsible for delivering the high frequency current components.
The sense resistors, RSx , should have a very low impedance
path to ground, because they must carry a large current while
supporting very accurate voltage measurements by the current
sense comparators. Long ground traces will cause additional
voltage drops, adversely affecting the ability of the comparators
to accurately measure the current in the windings. The SENSEx
pins have very short traces to the RSx resistors and very thick,
low impedance traces directly to the star ground underneath the
device. If possible, there should be no other components on the
sense circuits.
Solder
A4985
Trace (2 oz.)
Signal (1 oz.)
Ground (1 oz.)
PCB
OUT2B
OUT2A OUT1A
Thermal (2 oz.)
OUT1B
Thermal Vias
GND
OUT2B
ENABLE
C2
CAPACITANCE
VDD
VBB
C6
OUT1A
SENSE1
VBB1
SLEEP
ROSC
STEP
ROSC
BULK
RESET
GND
A4985
VCP
MS1
C4
REF
VREG
C4
DIR
GND
CP1
CP2
C6
OUT1B
PAD
GND
MS2
C3
GND
C1
C3
OUT2A
VBB2
OUT2B
U1
SENSE2
C7
GND
C7
OUT1B
R5
R4
R5
R4
OUT1A
OUT2A
VDD
C1
C2
ROSC
Figure 8: ES Package Typical Application and Circuit Layout
VDD
VBB
12
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DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
OUT2B
C3
U1
GND
C6
GND
C4
GND
C3
OUT2A
C5
R4
ROSC
R5
C4
C5
OUT1A
C1
GND
OUT1B
GND
GND
BULK
CAPACITANCE
C2
VDD
VCP
VREG
PAD
MS1
MS2
GND
VBB2
SENSE2
OUT2A
ROSC
SLEEP
VDD
STEP
C1
GND
ENABLE
OUT2B
CP2
RESET
ROSC
GND
A4985
CP1
REF
C6
R4
OUT1A
SENSE1
VBB1
R5
OUT1B
DIR
C2
GND
VDD
VBB
VBB
Figure 9: LP Package Typical Application and Circuit Layout
13
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
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DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
Pin Circuit Diagrams
VDD
VBB
VBB
8V
GND
GND
SENSE
GND
CP2
GND
GND
GND
GND
GND
VBB
10 V
CP1
40 V
PGND
VREG
VCP
VREG
DMOS
Parasitic
GND
8V
MS1
MS2
DIR
VREF
ROSC
SLEEP
VBB
OUT
DMOS
Parasitic
8V
GND
GND
DMOS
Parasitic
GND
14
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DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
RESET
STEP
STEP
100.00
Slow
70.71
–100.00
100.00
–70.71
–100.00
100.00
70.71
70.71
Phase 2
IOUT2A
Direction = H
(%)
Phase 2
IOUT2B
Direction = H
(%)
0.00
Slow
Mixed
Mixed
0.00
Home Microstep Position
–70.71
Home Microstep Position
0.00
Slow
Mixed
Phase 1
IOUT1A
Direction = H
(%)
Slow
Home Microstep Position
Phase 1
IOUT1A
Direction = H
(%)
Mixed*
70.71
Mixed*
Mixed*
Slow Slow
Mixed
Home Microstep Position
100.00
Mixed
Slow
Slow
Mixed
0.00
–70.71
–70.71
–100.00
–100.00
*With ROSC pin tied to GND
*With ROSC pin tied to GND
DIR= H
DIR= H
Figure 10: Decay Mode for Full-Step Increments
Figure 11: Decay Modes for Half-Step Increments
STEP
100.00
92.39
70.71
Slow
Slow
Mixed
–38.27
–70.71
–92.39
–100.00
100.00
92.39
Slow
Mixed*
70.71
Phase 2
IOUT2B
Direction = H
(%)
Mixed
0.00
Home Microstep Position
Phase 1
IOUT1A
Direction = H
(%)
Mixed*
38.27
38.27
Slow
Mixed
Slow
Mixed
Slow
Mixed
0.00
–38.27
–70.71
–92.39
–100.00
*With ROSC pin tied to GND
DIR= H
Figure 12: Decay Modes for Quarter-Step Increments
15
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
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DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
STEP
100.00
92.39
83.15
70.71
55.56
Mixed*
38.27
19.51
0.00
Slow
–19.51
–38.27
–55.56
–70.71
–83.15
–92.39
–100.00
100.00
92.39
83.15
70.71
55.56
Phase 2
IOUT2B
Direction = H
(%)
Mixed
0.00
Mixed
Mixed
Slow
Mixed*
38.27
19.51
Slow
Home Microstep Position
Phase 1
IOUT1A
Direction = H
(%)
Mixed
Slow
–19.51
–38.27
–55.56
–70.71
–83.15
–92.39
–100.00
*With ROSC pin tied to GND
DIR= H
Figure 13: Decay Modes for Eighth-Step Increments
16
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
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DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
Table 2: Step Sequencing Settings
Home microstep position at Step Angle 45º; DIR = H
Full
Step
#
Half
Step
#
1
1/4
Step
#
1
2
1
2
3
4
3
5
6
2
4
7
8
5
9
10
3
6
11
12
7
13
14
4
8
15
16
1/8
Step
#
1
Phase 1
Current
Phase 2
Current
Step
Angle
(º)
0.0
[% ItripMax]
[% ItripMax]
2
98.08
19.51
11.3
3
92.39
38.27
22.5
4
83.15
55.56
33.8
5
70.71
70.71
45.0
6
55.56
83.15
56.3
7
38.27
92.39
67.5
8
19.51
98.08
78.8
9
0.00
100.00
90.0
10
–19.51
98.08
101.3
11
–38.27
92.39
112.5
12
–55.56
83.15
123.8
13
–70.71
70.71
135.0
14
–83.15
55.56
146.3
15
–92.39
38.27
157.5
16
–98.08
19.51
168.8
17
–100.00
0.00
180.0
18
–98.08
–19.51
191.3
19
–92.39
–38.27
202.5
20
–83.15
–55.56
213.8
21
–70.71
–70.71
225.0
22
–55.56
–83.15
236.3
23
–38.27
–92.39
247.5
24
–19.51
–98.08
258.8
25
0.00
–100.00
270.0
26
19.51
–98.08
281.3
27
38.27
–92.39
292.5
28
55.56
–83.15
303.8
29
70.71
–70.71
315.0
30
83.15
–55.56
326.3
31
92.39
–38.27
337.5
32
98.08
–19.51
348.8
(%)
100.00
(%)
0.00
17
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
Pin-out Diagrams
1
18 OUT1B
ENABLE
2
17 DIR
GND
3
16 GND
CP1
4
CP2
5
14 STEP
VCP
6
13 VDD
1
2
3
4
5
6
7
CP2
8
24
23
22
21
20
19
18
PAD
VCP 9
VREG 10
MS1 11
MS2 12
RESET 13
ROSC 14
SLEEP 15
SLEEP 12
15 REF
ROSC 11
RESET 10
9
MS2
8
MS1
VREG
7
PAD
OUT2B
NC
VBB2
NC
ENABLE
GND
CP1
OUT1B
NC
VBB1
NC
CP1 1
24 GND
CP2 2
23 ENABLE
VCP 3
22 OUT2B
21 VBB2
VREG 4
20 SENSE2
MS1 5
MS2 6
PAD
RESET 7
DIR
GND
REF
17 STEP
ROSC 8
SLEEP 9
VDD 10
STEP 11
VDD 16
OUT2B
LP Package
29 NC
28 NC
27 OUT1A
26 NC
25 SENSE1
32 SENSE2
31 NC
30 OUT2A
ET Package
19 VBB1
20 SENSE1
21 OUT1A
22 OUT2A
23 SENSE2
24 VBB2
ES Package
REF 12
19 OUT2A
18 OUT1A
17 SENSE1
16 VBB1
15 OUT1B
14 DIR
13 GND
Terminal List Table
Name
Number
Description
ES
ET*
LP
CP1
4
7
1
Charge pump capacitor terminal
CP2
5
8
2
Charge pump capacitor terminal
DIR
17
20
14
Logic input
¯ B̄¯ L̄¯ Ē
¯
Ē¯ N̄¯ Ā
2
5
23
Logic input
GND
3, 16
6, 19
13, 24
MS1
8
11
5
Logic input
MS2
9
12
6
Logic input
NC
–
2, 4, 21, 23,
26, 28, 29, 31
–
No connection
Ground
OUT1A
21
27
18
DMOS Full Bridge 1 Output A
OUT1B
18
24
15
DMOS Full Bridge 1 Output B
OUT2A
22
30
19
DMOS Full Bridge 2 Output A
OUT2B
1
1
22
DMOS Full Bridge 2 Output B
REF
15
18
12
Gm reference voltage input
¯ S̄¯ Ē
¯ T̄
¯
R̄¯ Ē
10
13
7
Logic input
ROSC
11
14
8
Timing set
SENSE1
20
25
17
Sense resistor terminal for Bridge 1
SENSE2
23
32
20
Sense resistor terminal for Bridge 2
¯ L̄¯ Ē¯ Ē
¯ P̄
¯ S̄
12
15
9
Logic input
STEP
14
17
11
Logic input
VBB1
19
22
16
Load supply
VBB2
24
3
21
Load supply
VCP
6
9
3
Reservoir capacitor terminal
VDD
13
16
10
Logic supply
VREG
7
10
4
Regulator decoupling terminal
PAD
–
–
–
Exposed pad for enhanced thermal dissipation*
*The GND pins must be tied together externally by connecting to the PAD ground plane under the device.
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DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
ES Package, 24-Pin QFN with Exposed Thermal Pad
0.30
4.00 ±0.15
24
1
2
0.50
24
0.95
1
2
A
2.70
4.00 ±0.15
4.10
2.70
25X
D
SEATING
PLANE
0.08 C
+0.05
0.25 –0.07
0.75 ±0.05
0.50 BSC
C
4.10
C
PCB Layout Reference View
For Reference Only; not for tooling use (reference JEDEC MO-220WGGD)
Dimensions in millimeters
Exact case and lead configuration at supplier discretion within limits shown
A Terminal #1 mark area
B Exposed thermal pad (reference only, terminal #1
identifier appearance at supplier discretion)
0.45 MAX
B
2.70
2
1
C Reference land pattern layout (reference IPC7351
QFN50P400X400X80-25W6M)
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)
D Coplanarity includes exposed thermal pad and terminals
24
2.70
19
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
ET Package, 32-Contact QFN with Exposed Thermal Pad
5.00 ±0.15
32
32
1
2
0.30
0.50
1.00
1
2
A
5.00 ±0.15
3.40
5.00
1
33X
D
SEATING
PLANE
0.08 C
0.25±0.10
0.90 ±0.10
0.50 BSC
3.40
C
5.00
C
PCB Layout Reference View
For Reference Only; not for tooling use
(reference JEDEC MO-220VHHD-6)
Dimensions in millimeters
Exact case and lead configuration at supplier discretion within limits shown
0.50±0.10
3.40
B
2
1
32
3.40
A Terminal #1 mark area
B Exposed thermal pad (reference only, terminal #1
identifier appearance at supplier discretion)
C Reference land pattern layout (reference
IPC7351 QFN50P500X500X100-33V6M);
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)
D Coplanarity includes exposed thermal pad and terminals
20
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
LP Package, 24-Pin TSSOP with Exposed Thermal Pad
7.80 ±0.10
24
0.65
0.45
4° ±4
+0.05
0.15 –0.06
B
3.00±0.05 4.40 ±0.10
6.40 ±0.20
A
1
2
6.10
(1.00)
4.32±0.05
0.25
24X
SEATING
PLANE
0.10 C
+0.05
0.25 –0.06
3.00
0.60 ±0.15
0.65
1.20 MAX
0.15 MAX
C
SEATING PLANE
GAUGE PLANE
1.65
4.32
C
PCB Layout Reference View
For reference only
(reference JEDEC MO-153 ADT)
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
TSOP65P640X120-25M); 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)
21
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
DMOS Microstepping Driver with Translator
And Overcurrent Protection
A4985
Revision History
Revision
Revision Date
Description of Revision
4
March 21, 2012
5
May 7, 2014
Update example layout
Revised text on pp. 7, 9; revised Figure 10
Copyright ©2009-2014, 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 any devices or systems, including but not limited to life support devices or systems, in which a failure of
Allegro’s product can reasonably be expected to cause bodily harm.
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
22
Allegro MicroSystems, LLC
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www.allegromicro.com
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