ICS853S014I Datasheet, PDF (16/20 Pages) Integrated Device Technology – Two selectable differential LVPECL clock inputs

ICS853S014I Data Sheet
LOW SKEW, 1-TO-5, DIFFERENTIAL-TO-2.5V, 3.3V LVPECL/ECL FANOUT BUFFER
T3. Calculations and Equations.
The purpose of this section is to calculate the power dissipation for the LVPECL output pair.
LVPECL output driver circuit and termination are shown in Figure 7.
V_CC
Q1
V_OUT
RL
50Ω
V_CC - 2V
Figure 7. LVPECL Driver Circuit and Termination
To calculate power dissipation due to the load, use the following equations which assume a 50 load, and a termination voltage of V_CC – 2V.
• For logic high, V_OUT = V_{OH_MAX} = V_{CC_MAX} – 0.935V
(V_{CC_MAX} – V_{OH_MAX}) = 0.935V
• For logic low, V_OUT = V_{OL_MAX} = V_{CC_MAX} – 1.67V
(V_{CC_MAX} – V_{OL_MAX}) = 1.67V
Pd_H is power dissipation when the output drives high.
Pd_L is the power dissipation when the output drives low.
Pd_H = [(V_{OH_MAX} – (V_{CC_MAX} – 2V))/R_L] * (V_{CC_MAX} – V_{OH_MAX}) = [(2V – (V_{CC_MAX} – V_{OH_MAX}))/R_L] * (V_{CC_MAX} – V_{OH_MAX}) =
[(2V – 0.935V)/50] * 0.935V = 19.92mW
Pd_L = [(V_{OL_MAX} – (V_{CC_MAX} – 2V))/R_L] * (V_{CC_MAX} – V_{OL_MAX}) = [(2V – (V_{CC_MAX} – V_{OL_MAX}))/R_L] * (V_{CC_MAX} – V_{OL_MAX}) =
[(2V – 1.67V)/50] * 1.67V = 11.02mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 30.94mW
ICS853S014AGI REVISION D MAY 23, 2013
16
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