85354AK

www.icst.com/products/hiperclocks.html

REV. B JUNE 8, 2004

13

Integrated

Circuit

Systems, Inc.

ICS85354

PRELIMINARY

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 5.

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