This example shows how to calculate IC power dissipation for a configuration to estimate worst-case power dissipation. In this case, the maximum supply voltage and supply current values specified in Electrical Characteristics are used.

• Maximum V_CC = V_CCO = 3.465 V. Maximum I_CC and I_CCO values
• CLKin0/CLKin0* input is selected
• Banks A and B are configured for LVPECL: all outputs terminated with 50 Ω to V_T = V_CCO – 2 V
• REFout is enabled with 5-pF load
• T_A = 85°C

Using the maximum supply current and power calculations from the previous section, we can compute P_TOTAL and P_DEVICE.

• From Equation 6: I_{CC_TOTAL} = 10.5 mA + 27 mA + 27 mA + 5.5 mA = 70 mA
• From I_{CCO_PECL} max spec: I_{CCO_BANK_A} = I_{CCO_BANK_B} = 197 mA
• From Equation 8: P_TOTAL = 3.465 V × (70 mA + 197 mA + 197 mA + 10 mA) = 1642.4 mW
• From Equation 9: P_{RT_PECL} = ((2.57 V – 1.47 V)²/50 Ω) + ((1.72 V – 1.47 V)²/50 Ω) = 25.5 mW (per output pair)
• From Equation 10: P_{VTT_PECL} = 1.47 V × [ ((2.57 V – 1.47 V) / 50 Ω) + ((1.72 V – 1.47 V) / 50 Ω) ] = 39.5 mW (per output pair)
• From Equation 11: P_{RT_HCSL} = 0 mW (no HCSL outputs)
• From Equation 12: P_DEVICE = 1642.4 mW – (10 × (25.5 mW + 39.5 mW)) – 0 mW = 992.4 mW

In this worst-case example, the IC device will dissipate about 992.4 mW or 60% of the total power (1642.4 mW), while the remaining 40% will be dissipated in the LVPECL emitter resistors (255 mW for 10 pairs) and termination voltage (395 mW into V_CCO – 2 V).

Based on θ_JA of 28.5°C/W, the estimated die junction temperature would be about 28.3°C above ambient, or 113.3 °C when T_A = 85°C.