ICS853S01I Datasheet, PDF (17/23 Pages) Integrated Device Technology – One LVPECL output pair

ICS853S01I Data Sheet
2:1 DIFFERENTIAL-TO-LVPECL MULTIPLEXER
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 8.
V_CC
Q1
V_OUT
RL
50Ω
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} – 0.875V
(V_{CC_MAX} – V_{OH_MAX}) = 0.875V
• For logic low, V_OUT = V_{OL_MAX} = V_{CC_MAX} – 1.62V
(V_{CC_MAX} – V_{OL_MAX}) = 1.62V
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 – 0.875V)/50] * 0.875V = 19.691mW
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 – 1.62V)/50] * 1.62V = 12.31mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 32mW
ICS853S01AGI REVISION A OCTOBER 29, 2012
17
©2012 Integrated Device Technology, Inc.