HCPL-315J Datasheet, PDF (16/21 Pages) Agilent(Hewlett-Packard) – 0.5 Amp Output Current IGBT Gate Drive Optocoupler

16
The value of 4.25 mA for I_CC in
the previous equation was
obtained by derating the I_CC max
of 5 mA (which occurs at -40°C)
to I_CC max at 90°C (see Figure 7).
Since P_O for this case is greater
than P_O(MAX), Rg must be
increased to reduce the HCPL-
3150 power dissipation.
P_{O(SWITCHING MAX)}
= P_O(MAX) - P_O(BIAS)
= 154 mW - 85 mW
= 69 mW
E_SW(MAX) = –P–^O–⁽–^S–^W–^IT–^C_f–^H–^I–^N–^G–^M–^A–^X–⁾
= ^{6––9–m––W––} = 3.45 µJ
20 kHz
For Qg = 500 nC, from Figure
27, a value of E_SW = 3.45 µJ
gives a Rg = 41 Ω.
Thermal Model
(HCPL-3150)
The steady state thermal model
for the HCPL-3150 is shown in
Figure 28a. 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 flows through θ_CA
which raises the case temperature
T_C accordingly. The value of θ_CA
depends on the conditions of the
board design and is, therefore,
determined by the designer. The
value of θ_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-
3150 soldered into the center of
the board and still air. The
absolute maximum power
dissipation derating specifications
assume a θ_CAvalue of 83°C/W.
From the thermal mode in Figure
28a the LED and detector IC
junction temperatures can be
expressed as:
For example, given P_E = 45 mW,
P_O = 250 mW, T_A = 70°C and θ_CA
= 83°C/W:
T_JE = P_E^•313°C/W + P_D^• 132°C/W + T_A
= 45 mW^•313°C/W + 250 mW
•_{132°C/W + 70°C = 117°C}
T_JD = P_E^• 132°C/W + P_D^•187°C/W + T_A
= 45 mW^•132C/W + 250 mW
•_{187°C/W + 70°C = 123°C}
T_JE and T_JD should be limited to
125°C based on the board layout
and part placement (θ_CA) specific
to the application.
T_JE = P_E ^• (θ_LC||(θ_LD + θ_DC) + θ_CA)
( ) + P_D^• –_θ–_L–_C–₊–^θ–^L–_θ^C–_D^•–_C–^θ–₊^D–^C–_θ–_L–_D– + θ_CA + T_A
( ) T_JD = P_E –_θ–_L–_C–^θ–₊^L–^C–_θ–^•_D–_C^θ–^D₊–^C––_θ–_LD– + θ_CA
+ P_D^•(θ_DC||(θ_LD + θ_LC) + θ_CA) + T_A
Inserting the values for θ_LC and
θ_DC shown in Figure 28 gives:
T_JE = P_E^• (230°C/W + θ_CA)
+ P_D^•(49°C/W + θ_CA) + T_A
T_JD = P_E^•(49°C/W + θ_CA)
+ P_D^•(104°C/W + θ_CA) + T_A
θ_LD = 439°C/W
T_JE
T_JD
θ_LC = 391°C/W
θ_DC = 119°C/W
T_C
θ_CA = 83°C/W*
T_A
Figure 28a. Thermal Model.
T_JE = LED junction temperature
T_JD = detector IC junction temperature
T_C = case temperature measured at the center of the package bottom
θ_LC = LED-to-case thermal resistance
θ_LD = LED-to-detector thermal resistance
θ_DC = detector-to-case thermal resistance
θ_CA = case-to-ambient thermal resistance
∗θ_CA will depend on the board design and the placement of the part.