85322AM

www.icst.com/products/hiperclocks.html

REV. A JULY 31, 2001

10

Integrated

Circuit

Systems, Inc.

ICS85322

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.

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

)

Pd_L = [(V

OL_MAX

– (V

CC_MAX

- 2V))/R

L

] * (V

CC_MAX

- V

OL_MAX

)

•

For logic high, V

OUT

= V

OH_MAX

= V

CC_MAX

– 1.0V

Using V

CC_MAX

= 3.465, this results in V

OH_MAX

= 2.465V

•

For logic low, V

OUT

= V

OL_MAX

= V

CC_MAX

– 1.7V

Using V

CC_MAX

= 3.465, this results in V

OL_MAX

= 1.765V

Pd_H = [(2.465V - (3.465V - 2V))/50

Ω] * (3.465V - 2.465V) = 20mW

Pd_L = [(1.765V - (3.465V - 2V))/50

Ω] * (3.465V - 1.765V) = 10.2mW

Total Power Dissipation per output pair = Pd_H + Pd_L = 30.2mW

Q1

V

OUT

V

CC

RL

50

V