ICS8N3PG10MBKI-062 Datasheet, PDF (16/20 Pages) Integrated Device Technology – One differential LVPECL output pair

ICS8N3PG10MBKI-062 DATA SHEET
3. Calculations and Equations.
The purpose of this section is to calculate the power dissipation for the LVPECL output pair.
The 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 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} – 0.9V
(V_{CC_MAX} – V_{OH_MAX}) = 0.9V
• For logic low, V_OUT = V_{OL_MAX} = V_{CC_MAX} – 1.7V
(V_{CC_MAX} – V_{OL_MAX}) = 1.7V
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 – 0.9V)/50] * 0.9V = 19.8mW
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 – 1.7V)/50] * 1.7V = 10.2mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 30mW
PROGRAMMABLE FEMTOCLOCK^® NG DIFFERENTIAL-TO-3.3V, 2.5V
16
LVPECL SYNTHESIZER
REV A 05/15/14