ICS853014BGLF datasheet(13/17 Pages) ICST

13 / 17 page

853014BG

www.icst.com/products/hiperclocks.html

REV. C MAY 13, 2005

Integrated

Circuit

Systems, Inc.

ICS853014

LOW SKEW, 1-TO-5

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

3. Calculations and Equations.

LVPECL output driver circuit and termination are shown in

Figure 7.

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

– 0.935V

CC_MAX

- V

OH_MAX

) = 0.935V

•

For logic low, V

OUT

= V

OL_MAX

= V

CC_MAX

– 1.67V

CC_MAX

- V

OL_MAX

) = 1.67V

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 - 0.935V)/50

Ω] * 0.935V = 19.92mW

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 - 1.67V)/50

Ω] * 1.67V = 11.2mW

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

FIGURE 7. LVPECL DRIVER CIRCUIT AND TERMINATION

VOUT

VCC - 2V

VCC

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