14
Figure 27. Energy dissipated in the ACWN3190 for each IGBT switching cycle
Under Voltage Lockout Feature
The ACNW3190 contains an under voltage lockout
(UVLO) feature that is designed to protect the IGBT
under fault conditions which cause the ACNW3190
supply voltage (equivalent to the fully-charged IGBT
gate voltage) to drop below a level necessary to keep
the IGBT in a low resistance state. When the ACNW3190
output is in the high state and the supply voltage drops
below the ACNW3190 V
UVLO– threshold
(9.5 < V
UVLO–
<
12.0) the optocoupler output will go into the low state
with a typical delay, UVLO Turn O Delay, of 0.6 s. When
the ACNW3190 output is in the low state and the supply
voltage rises above the ACNW3190 V
UVLO+ threshold
(11.0
< V
UVLO+
< 13.5) the optocoupler output will go into the
high state (assumes LED is “ON”) with a typical delay,
UVLO Turn On Delay of 0.8 s.
Figure 28. Under Voltage Lock Out
Thermal Model
Introduction
For application which requires an output gate current
more than 2A, adequate PCB pad heat-sink must be
provided to dissipate the power loss in the package.
Failure to provide proper heat dissipation will potentially
damage the gate drive after pro-long usage. This thermal
model allows designer to compute the temperature of
the LED and detector.
De nitions
θ1:Thermal impedance from LED junction to ambient
θ2:Thermal impedance from LED to detector (output IC)
θ3:Thermal impedance from detector (output IC) junction
to ambient
Ambient Temperature: Measured approximately 1.25 cm
above the optocoupler, with no forced air.
Description
This thermal model assumes that an 8-pin single-channel
plastic package optocoupler is soldered into a 7.62 cm x
7.62 cm printed circuit board (PCB). The temperature at
the LED and Detector junctions of the optocoupler can
be calculated using the equations below.
∆TEA = A11*PE + A12*PD
∆TDA = A21*PE + A22*PD
where,
∆TEA = Temperature di erence between ambient and
LED
∆TDA = Temperature di erence between ambient and
detector
PE = Power dissipation from LED
PD = Power dissipation from detector
A11, A12, A21, A22 thermal coe cients (units in °C/W)
are functions of the thermal impedances θ1, θ2, θ3 (See
Note 2).
Table 1. Thermal Model-B Coe cient Data (units in °C/W)
S (cm) A11 A12, A21 A22
1 218.9 39.31 55.3
2 200.6 29.8 45
4 198 23.59 41.7
Jedec Speci cations A11 A12, A21 A22
low K board 254 50.3 66.8
High K board 151.2 16.72 39.06
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
0 10 20 30 40 50
Energy per cycle [ μJ ]
100 nC
500 nC
1000 nC
Rg [Ω]
V
O
– OUTPUT VOLTAGE – V
0
0
(V
CC
- V
EE
) – SUPPLY VOLTAGE – V
10
5
14
10 15
2
20
6
8
4
12
(12.3, 10.8)
(10.7, 9.2)
(10.7, 0.1)
(12.3, 0.1)
