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843081I-01 Datasheet, PDF (11/16 Pages) Integrated Device Technology – FemtoClock® Crystal-to-2.5V, 3.3V LVPECL Clock Multiplier | |||
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3. Calculations and Equations.
The purpose of this section is to derive the power dissipated into the load.
LVPECL output driver circuit and termination are shown in Figure 5.
843081I-01 DATA SHEET
FIGURE 5. LVPECL DRIVER CIRCUIT AND TERMINATION
To calculate worst case power dissipation into the load, use the following equations which assume a 50Ω load, and a
termination
voltage of VCC- 2V.
⢠For logic high, VOUT = VOH_MAX = VCC_MAX â 0.9V
(VCCO_MAX - VOH_MAX) = 0.9V
⢠For logic low, VOUT = VOL_MAX = VCC_MAX â 1.7V
(VCCO_MAX - VOL_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 = [(VOH_MAX â (VCC_MAX - 2V))/RL] * (VCC_MAX - VOH_MAX) = [(2V - (VCC_MAX - VOH_MAX))/RL] * (VCC_MAX - VOH_MAX) =
[(2V - 0.9V)/50Ω] * 0.9V = 19.8mW
Pd_L = [(VOL_MAX â (VCC_MAX - 2V))/RL] * (VCC_MAX - VOL_MAX) = [(2V - (VCC_MAX - VOL_MAX))/RL] * (VCC_MAX - VOL_MAX) =
[(2V - 1.7V)/50Ω] * 1.7V = 10.2mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 30mW
REVISION C 11/5/15
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FEMTOCLOCKS® CRYSTAL-TO-
3.3V, 2.5V LVPECL CLOCK MULTIPLIER
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