A3932SLDTR-T Allegro Microsystems Inc, A3932SLDTR-T Datasheet - Page 10

• Manufacturer Part Number: A3932SLDTR-T
• Description: 50V 3 PH BRUSHLESS MTR DC CTLR
• Manufacturer: Allegro Microsystems Inc

Specifications of A3932SLDTR-T

• Applications: DC Motor Controller, Brushless (BLDC), 3 Phase
• Number Of Outputs: 1
• Voltage - Supply: 18 V ~ 50 V
• Operating Temperature: -20°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 38-TSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Voltage - Load: -
• Lead Free Status / Rohs Status: Compliant
• Other names: 620-1291-2; A3932SLDTR-T

Synchronous Rectifi cation. To reduce power dissipation
in the external MOSFETs, the A3932 control logic turns on the
appropriate low-side and high-side driver during the load-current
recirculation, PWM-off cycle. Synchronous rectifi cation allows
current to fl ow through the MODE-selected MOSFET, rather
than the body diode, during the decay time. The body diodes of
the SR power MOSFETs will conduct only during the dead time
required at each PWM transition.
Dead Time. It is required to have a dead-time delay between a
high- or low-side turn off and the next turn-on event to prevent
cross conduction. The potential for cross conduction occurs with
synchronous rectifi cation, direction changes, PWM, or after a
bootstrap capacitor charging cycle. The dead time is set by a
resistor (R
(+5 V) and can be set between 100 ns and 5.5 μs.
and 470 kΩ. At 25°C,
For predicting worst case, over voltage and temperature
extremes,
For comparison with I
where (nominal values) V
R
ground (V
10 μA) current source.
resistance determines the selection of the dead-time resistor. The
dead time should be made long enough to cover the variation of
the MOSFET gate capacitance and series gate resistance (both
external and internal to the A3932) tolerances.
Decoupling. The internal reference, V
for the gate-drive circuit. As the gates are driven high they
will require current from an external capacitor to support the
transients. This capacitor should be placed as close as possible
to the V
than the bootstrap capacitor.
A3932
int
= 500 Ω.
The following equations are valid for R
Rather than use R
The choice of power MOSFET and external series gate
t
t
t
REG
dead
dead
dead
DEAD
dead
terminal. Its value should be at least 20 times larger
(nom, ns) = 37 + (11.9 x 10
(max, ns) = 63 + (17.2 x 10
(min, ns) = 10 + (6.55 x 10
) between the DEAD terminal and LCAP
I
DEAD
= 0 V), which activates an internal (I
= (V
DEAD
dead
LCAP
LCAP
values near 470 kΩ, set DEAD =
test currents,
– V
= 5 V, V
be
)/(R
be
-3
-3
-3
dead
REG
x (R
= 0.7 V at 25°C, and
x (R
x (R
dead
+ R
, supplies current
dead
dead
dead
int
between 5.6 kΩ
)
Applications Information
+ 350))
+ 500))
+ 650))
DEAD
Three-Phase Power MOSFET Controller
=
should be connected between LCAP and AGND as close to the
device terminals as possible.
Protection Circuitry. The A3932 has several protection
features:
1) Bootstrap Circuit. The bootstrap capacitor is charged
whenever a low-side MOSFET is on, Sx output goes low,
and the load current recirculates. This happens constantly
during normal operation. The high-side MOSFET will not be
allowed to turn on before the charging has decayed to less than
approximately 9 mA. No fault will be registered.
duty cycle operation) its charge pump is designed to maintain
V
< 10 μA.
2) Hall Invalid. Illegal codes for the HALL inputs (000 or
111) will force a fault and coast the motor. Noisy Hall lines
may cause double TACH pulses and, therefore, code errors that
produce faults. Additional external pullup loading and fi ltering
may be required depending on the system.
3) VREG Undervoltage. An internal regulator supplies the
low-side gate driver and the bootstrap charge current. It is critical
to ensure that V
outputs. The undervoltage circuit is active during power-up and
will force a motor coast condition (all gate drives, GHx and GLx =
0) until V
4) Thermal Shutdown. A junction temperature greater than
165°C will signal a fault and coast the motor (all gate drives
LOW). If the junction temperature then falls to less than 155°C
(hysteresis), the fault will be cleared.
5) Motor Lead Shorted to Ground. The A3932 will signal
a fault if a motor lead is shorted to ground. A short to ground
is assumed after a high side is turned on and greater than 2 V is
measured between the drain (V
high-side power MOSFET. This fault is cleared at the beginning
of each commutation. If a stalled motor results from a fault, the
fault can only be cleared by toggling the RESET terminal or by a
power-up sequence.
GS
Additionally, a 0.1 μF (or larger) decoupling capacitor
When a phase’s high-side driver is on for a long time (100%
> 9 V on the bridge FET if I
REG
is greater than approximately 9.7 V.
REG
is at the proper level before enabling any of the
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
BB
GHx
) and source (SA/SB/SC) of the
(the load on the gate driver)
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