873033AM

www.icst.com/products/hiperclocks.html

REV. A OCTOBER 19, 2005

12

Integrated

Circuit

Systems, Inc.

ICS873033

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 7.

Ω load, and a termination

voltage of V

CC

- 2V.

•

For logic high, V

OUT

= V

OH_MAX

= V

CC_MAX

–0.935V

(V

CC_MAX

- V

OH_MAX

) = 0.935V

•

For logic low, V

OUT

= V

OL_MAX

= V

CC_MAX

– 1.67V

(V

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

L

] * (V

CC_MAX

- V

OH_MAX

) = [(2V - (V

CC_MAX

- V

OH_MAX

))/R

L

] * (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

L

] * (V

CC_MAX

- V

OL_MAX

) = [(2V - (V

CC_MAX

- V

OL_MAX

))/R

L

] * (V

CC_MAX

- V

OL_MAX

) =

[(2V - 1.67V)/50

Ω] * 1.67V = 11.02mW

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

VOUT

Q1

VCC - 2V

RL

50

VCC