A3946KLP Allegro Microsystems Inc, A3946KLP Datasheet - Page 6

• Manufacturer Part Number: A3946KLP
• Description: IC CTRLR MOSFET 16-TSSOP
• Manufacturer: Allegro Microsystems Inc

Specifications of A3946KLP

• Applications: DC Motor Controller, Brushless (BLDC), 3 Phase
• Number Of Outputs: 1
• Voltage - Supply: 7 V ~ 60 V
• Operating Temperature: -40°C ~ 135°C
• Mounting Type: Surface Mount
• Package / Case: 16-TSSOP Exposed Pad, 16-eTSSOP, 16-HTSSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Current - Output: -
• Voltage - Load: -

A3946
VREG. A 13 V output from the on-chip charge pump, used
to power the low-side gate drive circuit directly, provides the
current to charge the bootstrap capacitors for the high-side gate
drive.
The VREG capacitor, C
rent to the gate of the low-side MOSFET. A 10 μF, 25 V capaci-
tor should be adequate. This capacitor can be either electrolytic
or ceramic (X7R).
Diagnostics and Protection. The fault output pin,
~FAULT, goes low (i.e., FAULT = 1) when the RESET line is
high and any of the following conditions are present:
• Undervoltage on VREG (UVREG). Note that the outputs
• Undervoltage on VREF (UVREF). Note that this condition
• A junction temperature > 170°C (OVERTEMP). This condi-
• An undervoltage on the stored charge of the BOOT capacitor
An overtemperature event signals a latched fault, but does not
disable any output drivers, regulators, or logic inputs. The user
must turn off the A3946 (e.g., force the RESET line low) to
prevent damage.
The power FETs are protected from inadequate gate drive
voltage by undervoltage detectors. Either of the regulator
undervoltage faults (UVREG or UVREF) disable both output
drivers until both voltages have been restored. The high-side
driver is also disabled during a UVBOOT fault condition.
Under many operating conditions, both the high-side (GH)
and low-side (GL) drivers may be off, allowing the BOOT
capacitor to discharge (or never become charged) and create a
UVBOOT fault condition, which in turn inhibits the high-side
driver and creates a FAULT = 1. This fault is NOT latched. To
remove this fault, momentarily turn on GL to charge the BOOT
capacitor.
Latched faults may be cleared by a low pulse, 1 to 10 μs
wide, on the RESET line. Throughout that pulse (despite a
become active as soon as VREG comes out of undervoltage,
even though the ~FAULT pin is latched until reset.
does
tion sets a latched fault.
(UVBOOT). This condition does NOT set a latched fault.
NOT
latch a fault.
REG
, must supply the instantaneous cur-
Functional Description
Half-Bridge Power MOSFET Controller
possible UVBOOT), FAULT = 0; also the fault latch is cleared
immediately, and remains cleared. If the power is restored
(no UVREG or UVREF), and if no OVERTEMP fault exists,
then the latched fault remains cleared when the RESET line
returns to high. However, FAULT = 1 may still occur because a
UVBOOT fault condition may still exist.
Charge Pump. The A3946 is designed to ac com mo date a
wide range of power supply voltages. The charge pump output,
VREG, is regulated to 13 V nominal.
In all modes, this regulator is current-limited. When V
the charge pump operates as a voltage doubler. When 8 V <
V
PWM, current-controlled, voltage regulator. When V
the charge pump operates as a PWM, current-controlled, volt-
age regulator. Effi ciency shifts, from 80% at V
at V
CAUTION. Although simple paralleling of VREG supplies
from several A3946s may appear to work correctly, such a
confi guration is NOT recommended. There is no assurance that
one of the regulators will not dominate, taking on all of the load
and back-biasing the other regulators. (For example, this could
occur if a particular regulator has an internal reference voltage
that is higher that those of the other regulators, which would
force it to regulate at the highest voltage.)
Sleep Mode/Power Up. In Sleep Mode, all circuits are
disabled in order to draw minimum current from VBB. When
powering up and leaving Sleep Mode (the RESET line is high),
the gate drive outputs stay disabled and a fault remains asserted
until VREF and VREG pass their undervoltage thresholds.
When powering up, before starting the fi rst bootstrap charge
cycle, wait until t = C
to allow the charge pump to stabilize.
When powered-up (not in Sleep Mode), if the RESET line is
low for > 10 μs, the A3946 may start to enter Sleep Mode (V
< 4 V). In that case, ~FAULT = 1 as long as the RESET line
remains low.
If the RESET line is open, the A3946 should go into Sleep
Mode. However, to ensure that this occurs, the RESET line
must be grounded.
BB
< 15 V, the charge pump operates as a voltage doubler/
BB
= 50 V.
REG
⁄ 4 (where C
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
REG
is in μF, and t is in ns)
BB
= 7 V, to 20%
BB
BB
>15 V,
< 8 V,
REF
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