UCC27423, UCC27424, UCC27425
SLUS545B − NOVEMBER 2002 − REVISED NOVEMBER 2004
APPLICATION INFORMATION
Source/Sink Capabilities During Miller Plateau
Large power MOSFETs present a large load to the control circuitry. Proper drive is required for efficient, reliable
operation. The UCC27423/4/5 drivers have been optimized to provide maximum drive to a power MOSFET
during the Miller plateau region of the switching transition. This interval occurs while the drain voltage is swinging
between the voltage levels dictated by the power topology, requiring the charging/discharging of the drain-gate
capacitance with current supplied or removed by the driver device.
[1]
Two circuits are used to test the current capabilities of the UCC27423 driver. In each case external circuitry is
added to clamp the output near 5 V while the IC is sinking or sourcing current. An input pulse of 250 ns is applied
at a frequency of 1 kHz in the proper polarity for the respective test. In each test there is a transient period where
the current peaked up and then settled down to a steady-state value. The noted current measurements are
made at a time of 200 ns after the input pulse is applied, after the initial transient.
The first circuit in Figure 2 is used to verify the current sink capability when the output of the driver is clamped
around 5 V, a typical value of gate-source voltage during the Miller plateau region. The UCC27423 is found to
sink 4.5 A at V
DD
= 15 V and 4.28 A at V
DD
= 12 V.
VDD
UCC27423
ENBA
INPUT
1
INA
ENBB
OUTA
8
DSCHOTTKY
7
C2
1
µ
F
C3
100
µ
F
+
VSUPPLY
5.5 V
10
Ω
2
3
GND
INB
VDD
OUTB
6
4
5
1
µ
F
CER
100
µ
F
AL EL
RSNS
0.1
Ω
VSNS
UDG−01065
Figure 3.
8
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