ICS853S011CI Datasheet, PDF (14/19 Pages) Integrated Device Technology – Maximum output frequency

ICS853S011CI Data Sheet
LOW SKEW, 1-TO-2, 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.
The LVPECL output driver circuit and termination are shown in Figure 5.
V_CCO
Q1
V_OUT
RL
50Ω
V_CCO - 2V
Figure 5. 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} – 0.99V
(V_{CC_MAX}– V_{OH_MAX}) = 0.99V
• For logic low, V_OUT = V_{OL_MAX} = V_{CC_MAX} – 1.6625V
(V_{CC_MAX}– V_{OL_MAX}) = 1.6625V
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_{CCO_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– 0.99V)/50] * 0.99V = 20mW
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 – 1.6625V)/50] * 1.6625V = 11.22mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 31.22mW
ICS853S011CGI REVISION A JULY 16, 2013
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©2013 Integrated Device Technology, Inc.