Broadcom

ACPL-K43CT-K44CT-DS100

13

ACPL-K43CT, ACPL-K44CT Data Sheet

Automotive R2Coupler™ Wide Operating Temperature 1-MBd Digital Optocoupler in a

Stretched 8-Pin Surface-Mount Plastic Package

Thermal Resistance Model for ACPL-K43CT

The diagram of ACPL-K43CT for measurement is shown in Figure 17. Here, one die is heated first 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

the case of two heat sources.

Figure 17: Diagram of ACPL-K43CT for Measurement

R11

R12

×

P1

=

ΔT1

R21

R22

P2

ΔT2

Measurement data on a low K board:

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)

Ta

: Ambient temperature (°C)

ΔT1

: Temperature difference between Die1 junction and ambient (°C)

ΔT2

: Temperature difference between Die2 junction and ambient (°C)

T1

= (R11 × P1 + R12 × P2 ) + Ta

T2

= (R21 × P1 + R22 × P2 ) + Ta

R11

R12

R21

R22

160°C/W

74°C/W

115°C/W