Datasheet

20
P
O
Parameter Description
I
CC
Supply Current
V
CC
Positive Supply Voltage
V
EE
Negative Supply Voltage
E
SW
(Rg,Qg) Energy Dissipated in the HCPL-3120
for each IGBT Switching Cycle
(See Figure 27)
f Switching Frequency
Figure 27. Energy dissipated in the HCPL-3120 for each IGBT switching
cycle.
Esw – ENERGY PER SWITCHING CYCLE – µJ
0
0
Rg – GATE RESISTANCE – Ω
50
6
10
HCPL-3120 fig 27
14
20
4
30 40
12
Qg = 100 nC
Qg = 500 nC
Qg = 1000 nC
10
8
2
V
CC
= 19 V
V
EE
= -9 V
Thermal Model (Discussion applies to HCPL-3120, HCPL-
J312 and HCNW3120)
The steady state thermal model for the HCPL-3120 is
shown in Figure 28. The thermal resistance values given
in this model can be used to calculate the temperatures
at each node for a given operating condition. As shown
by the model, all heat generated ows through q
CA
which
raises the case temperature T
C
accordingly. The value
of q
CA
depends on the conditions of the board design
and is, therefore, determined by the designer. The value
of q
CA
= 83°C/W was obtained from thermal measure-
ments using a 2.5 x 2.5 inch PC board, with small traces
(no ground plane), a single HCPL-3120 soldered into the
center of the board and still air. The absolute maximum
power dissipation derating specications assume a
q
CA
value of 83°C/W.
From the thermal mode in Figure 28 the LED and detector
IC junction temperatures can be expressed as:
T
JE
= P
E
@
(q
LC
||(q
LD
+ q
DC
) + q
CA
)
q
LC
* q
DC
+ P
D
•(——————— + q
CA
) + T
A
q
LC
+ q
DC
+ q
LD
q
LC
• q
DC
T
JD
= P
E
(——————— + q
CA
)
q
LC
+ q
DC
+ q
LD
+ P
D
• (q
DC
||(q
LD
+ q
LC
) + q
CA
) + T
A
Inserting the values for q
LC
and q
DC
shown in Figure 28
gives:
T
JE
= P
E
• (256°C/W + q
CA
)
+ P
D
• (57°C/W + q
CA
) + T
A
T
JD
= P
E
• (57°C/W + q
CA
)
+ P
D
• (111°C/W + q
CA
) + T
A
For example, given P
E
= 45 mW, P
O
= 250 mW, T
A
= 70°C
and q
CA
= 83°C/W:
T
JE
= P
E
• 339°C/W + P
D
• 140°C/W + T
A
= 45 mW • 339°C/W + 250 mW
• 140°C/W + 70°C = 120°C
T
JD
= P
E
• 140°C/W + P
D
• 194°C/W + T
A
= 45 mW • 140°C/W + 250 mW • 194°C/W + 70°C = 125°C
T
JE
and T
JD
should be limited to 125°C based on the
board layout and part placement (q
CA
) specic to the ap-
plication.
P
E
Parameter Description
I
F
LED Current
V
F
LED On Voltage
Duty Cycle Maximum LED Duty Cycle