Datasheet
UCC37321
ENBL
1
2
3
4 AGND
IN
7
6
5
8
OUT
OUT
PGND
INPUT
1 Fµ
CER
100 µF
AL EL
D
SCHOTTKY
VDD
C2
1 µF
V
SNS
R
SNS
0.1
Ω
C3
100 µF
10Ω
+
V
SUPPLY
5.5 V
VDDVDD
UCC37321
ENBL
1
2
3
4
IN
7
6
5
8
OUT
OUT
INPUT
VDD
VDD VDD
R
SNS
0.1 Ω
V
SNS
100 µF
AL EL
1 µF
CER
C2
1 µF
C3
100 µF
4.5 V
D
ADJ
D
SCHOTTKY
AGND
PGND
UCC27321-Q1, UCC27322-Q1
www.ti.com
SLUSA13C –FEBRUARY 2010–REVISED MARCH 2012
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 UCC27321/2 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.[1]
Two circuits are used to test the current capabilities of the UCC27321/2 driver. In each case, external circuitry is
added to clamp the output near 5 V while the device 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 when 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 circuit in Figure 27 is used to verify the current-sink capability when the output of the driver is clamped at
approximately 5 V, a typical value of gate-source voltage during the Miller plateau region. The UCC27321 is
found to sink 9 A at VDD = 15 V.
Figure 27. Sink Current Test Circuit
The circuit in Figure 28 is used to test the current-source capability with the output clamped to approximately 5 V
with a string of Zener diodes. The UCC27321 is found to source 9 A at VDD = 15 V.
Figure 28. Source Current Test Circuit
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