ICS8422002I-01 Datasheet, PDF (12/15 Pages) Integrated Circuit Systems – FEMTOCLOCKS™ CRYSTAL-TO-LVHSTL FREQUENCY SYNTHESIZER

ICS8422002I-01
FEMTOCLOCKS™ CRYSTAL-TO-LVHSTL FREQUENCY SYNTHESIZER
3. Calculations and Equations.
The purpose of this section is to derive the power dissipated into the load.
LVHSTL output driver circuit and termination are shown in Figure 5.
V_DDO
Q1
V_OUT
RL
50Ω
PRELIMINARY
Figure 5. LVHSTL Driver Circuit and Termination
To calculate worst case power dissipation into the load, use the following equations which assume a 50Ω load.
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} /R_L) * (V_{DDO_MAX} - V_{OH_MAX})
Pd_L = (V_{OL_MAX} /R_L) * (V_{DDO_MAX} - V_{OL_MAX})
Pd_H = (1.0V/50Ω) * (2V - 1.0V) = 20mW
Pd_L = (0.4V/50Ω) * (2V - 0.4V) = 12.8mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 32.8mW
IDT™ / ICS™ LVHSTL FREQUENCY SYNTHESIZER
12
ICS8422002AGI-01 REV. C NOVEMBER 1, 2007