A4982SETTR-T Allegro Microsystems Inc, A4982SETTR-T Datasheet - Page 7

• Manufacturer Part Number: A4982SETTR-T
• Description: IC STEPPER MOTOR DRIVER 32QFN
• Manufacturer: Allegro Microsystems Inc

Specifications of A4982SETTR-T

• Applications: Stepper Motor Driver
• Number Of Outputs: 1
• Current - Output: ±2A
• Voltage - Load: 8 V ~ 35 V
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -20°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-VFQFN Exposed Pad
• Motor Type: Stepper
• No. Of Outputs: 2
• Output Current: 2A
• Output Voltage: 35V
• Supply Voltage Range: 3V To 5.5V
• Driver Case Style: QFN
• No. Of Pins: 32
• Operating Temperature Range: -20°C To +85°C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 620-1340-2

A4982
Device Operation.
motor driver with a built-in translator for easy operation with
minimal control lines. It is designed to operate bipolar step-
per motors in full-, half-, quarter-, and sixteenth-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 (R
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 MSx 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 auto-
matic current decay selection improves microstepping perfor-
mance by reducing the distortion of the current waveform that
results from the back EMF of the motor.
Microstep Select
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
a 33.3 kΩ pull-down resistance. When changing the step mode the
change does not take effect until the next STEP rising edge.
If the step mode is changed without a translator reset, and abso-
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
order to avoid missing steps. When the device is powered down,
or reset due to TSD or an overcurrent event the translator is set to
the home position which is by default common to all step modes.
(MS1 and MS2). The microstep resolu-
The A4982 is a complete microstepping
S1
and R
S2
), a reference voltage (V
DMOS Microstepping Driver with Translator
Functional Description
REF
),
Low Current Microstepping.
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.
Reset Input ( ¯ R ¯ ¯ E ¯ ¯ S ¯ ¯ E ¯ ¯ T ¯ ).
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
the ¯ R ¯ ¯ E ¯ ¯ S ¯ ¯ E ¯ ¯ T ¯ input is set to high.
Step Input
input sequences the translator and advances the motor one incre-
ment. The translator controls the input to the DACs and the direc-
tion of current flow in each winding. The size of the increment is
determined by the combined state of inputs MS1 and MS2.
Direction Input
tion of the motor. Changes to this input do not take effect until the
next STEP rising edge.
Internal PWM Current Control.
trolled by a fixed off-time PWM current control circuit that limits
the load current to a desired value, I
of source and sink FET outputs are enabled and current flows
through the motor winding and the current sense resistor, R
When the voltage across R
current sense comparator resets the PWM latch. The latch then
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
R
tion is approximated by the maximum value of current limiting,
I
where R
the input voltage on the REF pin (V).
TripMAX
Sx
and the voltage at the VREF pin. The transconductance func-
S
(A), which is set by
And Overcurrent Protection
is the resistance of the sense resistor (Ω) and V
(STEP)
I
(DIR). This determines the direction of rota-
TripMAX
.
A low-to-high transition on the STEP
Sx
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
= V
The ¯ R ¯ ¯ E ¯ ¯ S ¯ ¯ E ¯ ¯ T ¯ input sets the translator
equals the DAC output voltage, the
REF
TRIP
/ ( 8
Intended for applications
Each full-bridge is con-
. Initially, a diagonal pair

R
S
)
REF
Sx
.
is
7