ICS85314AM01 datasheet(11/15 Pages) ICST

11 / 15 page

85314AG-01

www.icst.com/products/hiperclocks.html

REV. B JUNE 21, 2002

Integrated

Circuit

Systems, Inc.

ICS85314-01

LOW SKEW, 1-TO-5

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

PRELIMINARY

3. Calculations and Equations.

LVPECL output driver circuit and termination are shown in

Figure 4.

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 4 - LVPECL DRIVER CIRCUIT AND TERMINATION

OUT

CC - 2V

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