ICS853111B datasheet(14/18 Pages) ICST

14 / 18 page

853111BY

www.icst.com/products/hiperclocks.html

REV. A JUNE 16, 2005

Integrated

Circuit

Systems, Inc.

ICS853111B

LOW SKEW, 1-TO-10

DIFFERENTIAL-TO-2.5V/3.3V LVPECL/ECL FANOUT BUFFER

3. Calculations and Equations.

LVPECL output driver circuit and termination are shown in Figure 8.

To calculate worst case power dissipation into the load, use the following equations which assume a 50Ω load, and a termination

voltage of V

CCO

- 2V.

•

For logic high, V

OUT = VOH_MAX = VCCO_MAX – 0.935V

CC_MAX - VOH_MAX

) = 0.935V

•

For logic low, V

OUT = VOL_MAX = VCCO_MAX – 1.67V

CCO_MAX - VOL_MAX

) = 1.67V

Pd_H = [(V

OH_MAX – (VCCO_MAX - 2V))/RL

] * (V

CCO_MAX - VOH_MAX) = [(2V - (VCCO_MAX

- V

OH_MAX

))/R

] * (V

CCO _MAX- VOH_MAX) =

[(2V - 0.935V)/50Ω] * 0.935V = 19.92mW

Pd_L = [(V

OL_MAX – (VCCO_MAX - 2V))/RL

] * (V

CCO_MAX - VOL_MAX) = [(2V - (VCCO_MAX

- V

OL_MAX

))/R

] * (V

CCO_MAX - VOL_MAX) =

[(2V - 1.67V)/50Ω] * 1.67V = 11.02mW

Total Power Dissipation per output pair = Pd_H + Pd_L = 30.94mW

Figure 8. LVPECL Driver Circuit and Termination

VCCO - 2V

VOUT

VCCO

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