HCPL-3150 Datasheet, PDF (12/15 Pages) Agilent(Hewlett-Packard) – 0.5 Amp Output Current IGBT Gate Drive Optocoupler

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–⁽–^SW––^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
The steady state thermal model
for the HCPL-3150 is shown in
Figure 28. The thermal resistance
values given in this model can be
used to calculate the tempera-
tures 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 shown in Figure 29. The HCPL-
28 the LED and detector IC
3150 improves CMR performance
junction temperatures can be
by using a detector IC with an
expressed as:
optically transparent Faraday
shield, which diverts the capaci-
T_JE = P_E ^• (θ_LC||(θ_LD + θ_DC) + θ_CA)
tively coupled current away from
( ) + P_D^•
–_θ–_L–_C–₊–^θ–^L–_θ^C–_D–^•_C–^θ–₊^D–^C–_θ–_L–_D– + θ_CA
the sensitive IC circuitry. How
+ T_{A ever, this shield does not}
eliminate the capacitive coupling
( ) T_JD = P_E –_θ–_L–_C–^θ₊–^L–^C–_θ–^•_D–_C^θ–^D₊–^C––_θ–_LD– + θ_CA
between the LED and optocoup-
ler pins 5-8 as shown in
Figure 30. This capacitive
+ P_D^•(θ_DC||(θ_LD + θ_LC) + θ_CA) + T_A
coupling causes perturbations in
the LED current during common
Inserting the values for θ_LC and
θ_DC shown in Figure 28 gives:
mode transients and becomes the
major source of CMR failures for
a shielded optocoupler. The main
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
design objective of a high CMR
LED drive circuit becomes
keeping the LED in the proper
state (on or off) during common
mode transients. For example,
For example, given P_E = 45 mW,
P_O = 250 mW, T_A = 70°C and θ_CA
= 83°C/W:
the recommended application
circuit (Figure 25), can achieve
15 kV/µs CMR while minimizing
component complexity.
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}
Techniques to keep the LED in
the proper state are discussed in
the next two sections.
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.
LED Drive Circuit
Considerations for Ultra
High CMR Performance
Without a detector shield, the
dominant cause of optocoupler
CMR failure is capacitive
coupling from the input side of
the optocoupler, through the
package, to the detector IC as
7
Qg = 100 nC
6
Qg = 250 nC
Qg = 500 nC
5
4
V_CC = 19 V
V_EE = -9 V
3
2
1
0
0
20
40
60 80 100
Rg – GATE RESISTANCE – Ω
Figure 27. Energy Dissipated in the
HCPL-3150 for Each IGBT Switching
Cycle.
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