ICS853S9252I Datasheet, PDF (15/21 Pages) Integrated Device Technology – 2.5V, 3.3V ECL/LVPECL Clock/Data Fanout Buffer

ICS853S9252I Datasheet
2.5V, 3.3V ECL/LVPECL CLOCK/DATA FANOUT BUFFER
3. Calculations and Equations.
The purpose of this section is to calculate the power dissipation for the LVPECL output pairs.
The LVPECL output driver circuit and termination are shown in Figure 8.
V_CC
Q1
V_OUT
RL
V_CC - 2V
Figure 8. LVPECL Driver Circuit and Termination
To calculate worst case power dissipation into 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} – 0.76V
(V_{CC_MAX} – V_{OH_MAX}) = 0.76V
• For logic low, V_OUT = V_{OL_MAX} = V_{CC_MAX} – 1.6V
(V_{CC_MAX} – V_{OL_MAX}) = 1.6V
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 – 0.76V)/50] * 0.76V = 18.8mW
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 – 1.6V)/50] * 1.6V = 12.8mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 31.6mW
ICS853S9252BKI JUNE 14, 2017
15
©2017 Integrated Device Technology, Inc.