SiC783ACD
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Vishay Siliconix
S14-1639-Rev. B, 25-Aug-14
7
Document Number: 64902
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Shoot-Through Protection and Adaptive Dead Time
(AST)
The SiC783A has an internal adaptive logic to avoid shoot
through and optimize dead time. The shoot through
protection ensures that both high-side and low-side
MOSFETs are not turned on at the same time. The adaptive
dead time control operates as follows. The HS and LS gate
voltages are monitored to prevent the one turning on from
tuning on until the other's gate voltage is sufficiently low
(< 1 V). Built in delays also ensure that one power MOS is
completely off, before the other can be turned on. This
feature helps to adjust dead time as gate transitions change
with respect to output current and temperature.
Under Voltage Lockout (UVLO)
During the start up cycle, the UVLO disables the gate drive
holding high-side and low-side MOSFET gate low until the
input voltage rail has reached a point at which the logic
circuitry can be safely activated. The SiC783A also
incorporates logic to clamp the gate drive signals to zero
when the UVLO falling edge triggers the shutdown of the
device. As an added precaution, a 20 kΩ resistor is
connected between GH and PHASE to provide a discharge
path for the HS MOSFET.
FUNCTIONAL BLOCK DIAGRAM
Fig. 3 - SiC783A Functional Block Diagram
PWM
C
GND
20K
BOOT GH
V
SWH
GL
P
GND
+
-
V
ref
= 1 V
V
ref
= 1 V
GL
+
-
Anti-cross
conduction
control logic
V
DRV
PWM logic
control & state
machine
UVLO
Thermal monitor
& warning
THWn
ZCD_EN#
V
IN
PHASE
+
-
V
SWH
V
SWH
V
CIN
DSBL #
V
DRV
