843AG-106

www.icst.com/products/hiperclocks.html

REV. A JANUARY 10, 2006

9

Integrated

Circuit

Systems, Inc.

ICS843-106

3. Calculations and Equations.

The purpose of this section is to derive the power dissipated into the load.

LVPECL output driver circuit and termination are shown in Figure 3.

Ω load, and a

termination

voltage of V

CC

- 2V.

•

For logic high, V

OUT

= V

OH_MAX

= V

CC_MAX

– 0.9V

(V

CCO_MAX

- V

OH_MAX

) = 0.9V

•

For logic low, V

OUT

= V

OL_MAX

= V

CC_MAX

– 1.7V

(V

CCO_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

L

] * (V

CC_MAX

- V

OH_MAX

) = [(2V - (V

CC_MAX

- V

OH_MAX

))/R

L

] * (V

CC_MAX

- V

OH_MAX

) =

[(2V - 0.9V)/50

Ω] * 0.9V = 19.8mW

Pd_L = [(V

OL_MAX

– (V

CC_MAX

- 2V))/R

L

] * (V

CC_MAX

- V

OL_MAX

) = [(2V - (V

CC_MAX

- V

OL_MAX

))/R

L

] * (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 = 30mW

Q1

V

OUT

V

CC

RL

50

V