LMK00301 Datasheet, PDF (22/26 Pages) Texas Instruments – 3-GHz, 10-Output Differential Fanout Buffer / Level Translator

14.4.1.1 Power Dissipation Example
As an example, let us calculate the typical IC power dissipation at T_A = 25 °C for the following device configuration:
• Core supply voltage is 3.3 V and Output supply voltage is 2.5 V.
• CLKin0/CLKin0* input is selected.
• Bank A is configured for DC-coupled LVPECL: 4 pairs used with R_T = 50 Ω to V_T = Vcco – 2 V (1 pair unused).
• Bank B is configured for LVDS: 3 pairs used with R_L = 100 Ω differential (2 pairs unused).
• REFout is disabled.
Using the current and power calculations from the previous section, we can compute P_TOTAL and P_DEVICE.
• From Equation 5: I_{CC_TOTAL} = 8.5 mA + 20 mA + 26 mA + 0 mA = 54.5 mA
• From Table 5: I_{OUT_LOAD} (LVPECL) = (1.6 V – 0.5 V)/50 Ω + (0.75 V – 0.5 V)/50 Ω = 27 mA
• From Equation 7: I_{CCO_BANK_A} = 33 mA + (4 * 27 mA) = 141 mA
• From Equation 6: I_{CCO_TOTAL} = 141 mA + 34 mA + 0 mA = 175 mA
• From Equation 8: P_TOTAL = (3.3 V * 54.5 mA) + (2.5 V * 175 mA) = 617 mW
• From Equation 9: P_{RT_PECL} = ((1.6 V – 0.5 V)²/50 Ω) + ((0.75 V – 0.5 V)²/50 Ω) = 25.5 mW (per output pair)
• From Equation 10: P_{VTT_PECL} = 0.5 V * [ ((1.6 V – 0.5 V) / 50 Ω) + ((0.75 V – 0.5 V) / 50 Ω) ] = 13.5 mW (per output pair)
• From Equation 11: P_{RT_HCSL} = 0 mW (no HCSL outputs)
• From Equation 12: P_DEVICE = 617 mW – (4 * (25.5 mW + 13.5 mW)) – 0 mW = 461 mW
In this example configuration, the IC device will dissipate about 461 mW or 75% of the total power (617 mW), while the remaining
25% will be dissipated in the emitter resistors (102 mW for 4 pairs) and termination voltage (54 mW into Vcco – 2 V).
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