ICS853S004I Datasheet, PDF (16/20 Pages) Integrated Device Technology – Low Skew, 1-to-4, Differential-to-2.5V, 3.3V LVPECL Fanout Buffer

ICS853S004I Data Sheet
LOW SKEW, 1-TO-4, DIFFERENTIAL-TO-2.5V, 3.3V LVPECL/ECL FANOUT BUFFER
3. 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 8.
V_CC
Q1
V_OUT
RL
50Ω
V_CC - 2V
Figure 8. LVPECL Driver Circuit and Termination
To calculate output power dissipated due to loading, 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} – 0.815V
(V_{CC_MAX} – V_{OH_MAX}) = 0.815V
• 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 – 0.815V)/50] * 0.815V = 19.32mW
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 = 30.34mW
ICS853S004AKI May 27, 2017
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©2017 Integrated Device Technology, Inc.