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ACPL-K34T-500E

P1-P3P4-P6P7-P9P10-P12P13-P15
13
To prevent cross-conduction between high side and low side power transistors, minimum dead time (DT MIN) must
be introduced to the system. For example, given DTD MIN = -40 ns and DTD MAX = 50 ns, if designers target to have
minimum dead time (DT MIN) of 20 ns after the optocoupler, then initial dead time (DT) needed for the system can be
calculated as:
DT = DT MIN – DTD MIN
= 20ns – (-40ns)
= 60ns
Maximum dead time (DT MAX) after the optocoupler can be calculated as:
DT MAX = DT + DTD MAX
= 60 ns + 50 ns
= 110 ns
By introducing DT = 60 ns, the overall system dead time can vary from 20 ns to 110 ns due to the optocoupler’s DTD.
Note: The propagation delays used to calculate dead time distortion (DTD) are taken at equal temperatures and test
conditions since the optocouplers used are typically mounted close to each other and are switching the same type of
MOSFETs.
14
Thermal Resistance Model for ACPL-K34T
The diagram for measurement is shown in Figure 23. Here, one die is heated rst and the temperatures of all the dice are
recorded after thermal equilibrium is reached. Then, the second die is heated and all the dice temperatures are recorded.
With the known ambient temperature, the die junction temperature and power dissipation, the thermal resistance can
be calculated. The thermal resistance calculation can be cast in matrix form. This yields a 2 by 2 matrix for our case of
two heat sources.
R11 R12
•
P1
=
∆
T1
R21 R22 P2 ∆T2
Figure 23. Diagram of ACPL-K34T for measurement
R11: Thermal Resistance of Die1 due to heating of Die1 (°C/W)
R12: Thermal Resistance of Die1 due to heating of Die2 (°C/W)
R21: Thermal Resistance of Die2 due to heating of Die1 (°C/W)
R22: Thermal Resistance of Die2 due to heating of Die2 (°C/W)
P1: Power dissipation of Die1 (W)
P2: Power dissipation of Die2 (W)
T1: Junction temperature of Die1 due to heat from all dice (°C)
T2: Junction temperature of Die2 due to heat from all dice (°C)
T
A
: Ambient temperature (˚C)
∆T1: Temperature dierence between Die1 junction and ambient (˚C)
∆T2: Temperature deference between Die2 junction and ambient (°C)
T1 = (R11 × P1 + R12 × P2) + T
A
------------------(1)
T2 = (R21 × P1 + R22 × P2) + T
A
------------------(2)
Measurement is done on both low and high conductivity boards as shown below:
Layout Measurement data
Low conductivity board:
R11=191 ˚C/W
R12=R21= 68.5˚C/W
R22=77˚C/W
High conductivity board:
R11=155 ˚C/W
R12=R21= 64˚C/W
R22=41˚C/W
Note that the above thermal resistance R11, R12, R21 and R22 can be improved by increasing the ground plane/copper
area.
1
2
3
4
8
7
6
5
Die1:
LED
Die 2:
Detector
76mm
79mm
For product information and a complete list of distributors, please go to our web site: www.avagotech.com
Avago, Avago Technologies, the A logo, and R
2
Coupler are trademarks of Avago Technologies in the United States and other countries.
Data subject to change. Copyright © 2005-2013 Avago Technologies. All rights reserved.
AV02-4229EN - September 16, 2013
Application and environment design for ACPL-K34T needs to ensure that the junction temperature of the internal IC
and LED within the gate drive optocoupler do not exceed 150 °C. The equation (1) and (2) provided above are for the
purposes of estimating the junction temperatures. For example:
Calculation of LED and output IC power dissipation
LED power dissipation, P
E
= I
F(LED)
(Recommended Max) * V
F(LED)
(at 125 °C) * Duty Cycle
= 13 mA * 1.25 V * 50%
= 8.125 mW
Output IC power dissipation, P
O
= V
CC
(Recommended Max) * I
CC
(Max) + P
HS
+ P
LS
= 20 V * 4 mA + 53.3 mW + 32 mW
= 165.3 mW
where PHS = High side switching power dissipation
= (V
CC
* Q
G
* f
PWM
)* R
DS,OH(MAX)
/ (R
DS,OH(MAX)
+ R
GH
) /2
= (20 V * 80nC * 200 kHz) * 4Ω/(4Ω+8Ω)/2
= 53.3mW
PLS = Low side switching power dissipation
= (V
CC
* Q
G
* f
PWM
)* R
DS,OL(MAX)
/ (R
DS,OL(MAX)
+ R
GL
) /2
= (20 V * 80 nC * 200 kHz) * 2Ω/(2Ω+8Ω)/2
= 32 mW
Q
G
= Gate charge at supply voltage
f
PWM
= LED switching frequency
R
GH
= Gate charging resistance
R
GL
= Gate discharging resistance
Calculation of LED junction temperature and output IC junction temperature at Ta=125 °C:
LED junction temperature,
T1 = (R11 × P
E
+ R12 × P
O
) + T
A
= (191°C/W * 8.125 mW + 68.5 °C/W * 165.3 mW) + 125 °C
= 138 °C < T
J
(absolute max) of 150 °C
Output IC junction temperature,
T2 = (R21 × P
E
+ R22 × P
O
) + T
A
= (68.5 °C/W * 8.125 mW + 77 °C/W * 165.3 mW) + 125 °C
= 138 °C < T
J
(absolute max) of 150 °C
P1-P3P4-P6P7-P9P10-P12P13-P15

ACPL-K34T-500E

Mfr. #:
Buy ACPL-K34T-500E
Manufacturer:
Broadcom / Avago
Description:
High Speed Optocouplers OPTOCOUPLER AUTOMOTIVE TR LF
Lifecycle:
New from this manufacturer.
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