A3980 Allegro MicroSystems, Inc., A3980 Datasheet - Page 10

• Manufacturer Part Number: A3980
• Description: Automotive DMOS Microstepping Driver with Translator
• Manufacturer: Allegro MicroSystems, Inc.

as shown in table 3. In all other modes, V
allowed to exceed 4 V, because the peak sense value can
reach V
Fixed Off-Time.
circuitry uses a one-shot circuit to control the duration of
time that the DMOS FETs remain off. The one shot off-time,
t
nation of an external resistor (R
combination is connected from the timing terminal RC1 to
ground, and the other similarly connected to RC2 . t
is approximated by
over a range of values from C
R
RC Blanking.
PWM control circuit, the C
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, and switching tran-
sients related to the capacitance of the load. The blank time,
t
where C
The blank time should be as short as possible, without caus-
ing a false fault detection, to ensure that power dissipation
during a fault condition is minimized. The blank time also
defi nes the minimum duration of time that the full-bridge
DMOS outputs cause the load current to rise. To ensure
correct detection of motor faults, the minimum on-time is
extended by an additional fault sampling time, t
minimum on-time, t
Charge Pump
used to generate a gate supply greater than that of VBB for
driving the source-side DMOS gates. A 100 nF ceramic
OFF
BLANK
T
= 12 kΩ to 100 kΩ.
, is determined for each of the two phases by the combi-
REF
(ns), can be approximated by
T
is the value of the capacitor C
⁄ 8, or 100%.
In addition to the fi xed off-time of the
(CP1 and CP2). The charge pump is
t
MINON
MINON
t
The internal PWM current control
BLANK
t
OFF
= t
is then
T
= R
= 1400
component sets the comparator
BLANK
Automotive DMOS Microstepping Driver with Translator
T
= 470 pF to 1500 pF and from
T
T
) and a capacitor (C
×
×
C
+ t
T
C
SCT
T
T
REF
(nF).
should not be
SCT
. The
OFF
T
). One
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(ns)
capacitor (C
age VBATT, should be connected between CP1 and CP2.
In addition, a 100 nF ceramic capacitor (C
between VCP and VBB, to act as a reservoir for operating
the high-side DMOS devices. The voltage on C
the charge pump voltage, which is always less than 10 V.
VREG
to operate the sink-side DMOS FETs. The VREG terminal
must be decoupled with a 220 nF (10V) capacitor to ground.
VREG is internally monitored. In the case of a fault condi-
tion, the DMOS outputs of the A3980 are disabled.
Enable Input
of the DMOS 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 the ENABLE input
state.
Sleep Mode
when the motor is not in use, this input disables much of the
internal circuitry including the output DMOS FETs, voltage
regulator, and charge pump. A logic low on the SLEEP ter-
minal puts the A3980 into Sleep mode. A logic high allows
normal operation, as well as start-up (at which time the
A3980 drives the motor to the Home microstep position).
Percent Fast Decay Input
signal commands an output current level that is lower than
that of the previous step, it switches the output current decay
to slow, fast, or mixed decay mode, depending on the voltage
level at the PFD input, as shown in the following table.
Mixed Decay Operation.
sequence, if the voltage on the PFD pin is between
0.6
(0.21
×
V
×
(VREG)
DD
V
V
V
Lower PFD Input
PFD
PFD
DD
and 0.21
CP
Voltage Level
), capable of withstanding the battery volt-
) ≤ V
< (0.21
> (0.6
(SLEEP). To minimize power consumption
.
(ENABLE)
This internally-generated voltage is used
PFD
×
×
×
≤ (0.6
V
V
V
DD
DD
DD
)
, the full-bridge can operate in
)
×
.
This input simply turns off all
V
Depending on the step
DD
(PFD)
)
.
When a STEP input
CS
Decay Mode
)is required
Mixed
CS
A3980
Slow
Fast
is limited to
10