85301AK

www.icst.com/products/hiperclocks.html

REV. A JANUARY 16, 2006

14

Integrated

Circuit

Systems, Inc.

ICS85301

2:1

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 6.

Ω load, and a termination

voltage of V

CC

- 2V.

•

For logic high, V

OUT

= V

OH_MAX

= V

CC_MAX

– 1.005V

(V

CC_MAX

- V

OH_MAX

) = 1.005

•

For logic low, V

OUT

= V

OL_MAX

= V

CC_MAX

– 1.78V

(V

CC_MAX

- V

OL_MAX

) = 1.78V

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 - 1.005V)/50

Ω] * 1.005V = 20mW

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 - 1.78V)/50

Ω] * 1.78V = 7.83mW

Total Power Dissipation per output pair = Pd_H + Pd_L = 27.83mW

VOUT

Q1

VCC - 2V

RL

50

VCC