ICS5314AI11L datasheet(13/18 Pages) ICST

13 / 18 page

85314AGI-11

www.icst.com/products/hiperclocks.html

REV. C MAY 24, 2005

Integrated

Circuit

Systems, Inc.

ICS85314I-11

LOW SKEW, 1-TO-5

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

3. Calculations and Equations.

LVPECL output driver circuit and termination are shown in Figure 6.

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

Ω load, and a termination

voltage of V

- 2V.

•

For logic high, V

OUT

= V

OH_MAX

= V

CC_MAX

– 1.0V

CC_MAX

- V

OH_MAX

) = 1.0V

•

For logic low, V

OUT

= V

OL_MAX

= V

CC_MAX

– 1.7V

CC_MAX

- V

OL_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 = [(V

OH_MAX

– (V

CC_MAX

- 2V))/R

] * (V

CC_MAX

- V

OH_MAX

) = [(2V - (V

CC_MAX

- V

OH_MAX

))/R

] * (V

CC_MAX

- V

OH_MAX

) =

[(2V - 1V)/50

Ω] * 1V = 20.0mW

Pd_L = [(V

OL_MAX

– (V

CC_MAX

- 2V))/R

] * (V

CC_MAX

- V

OL_MAX

) = [(2V - (V

CC_MAX

- V

OL_MAX

))/R

] * (V

CC_MAX

- V

OL_MAX

) =

[(2V - 1.7V)/50

Ω] * 1.7V = 10.2mW

Total Power Dissipation per output pair = Pd_H + Pd_L = 30.2mW

FIGURE 6. LVPECL DRIVER CIRCUIT AND TERMINATION

OUT

CC - 2V

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