8525BG

www.icst.com/products/hiperclocks.html

REV. B JULY 27, 2001

9

Integrated

Circuit

Systems, Inc.

ICS8525

3. Calculations and Equations.

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

LVHSTL output driver circuit and termination are shown in

Figure 8.

To calculate worst case power dissipation into the load, use the following equations which assume a 50

Ω load, and a

termination voltage of V

DD

- 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

/R

L

) * (V

DD_MAX

- V

OH_MAX

)

Pd_L = (V

OL_MAX

/R

L

) * (V

DD_MAX

- V

OL_MAX

)

•

For logic high, V

OUT

= V

OH_MAX

= V

DD_MAX

– 1.2V

•

For logic low, V

OUT

= V

OL_MAX

= V

DD_MAX

– 0.4V

Pd_H = (1.2V/50

Ω) * (2V - 1.2V) = 19.2mW

Pd_L = (0.4V/50

Ω) * (2V - 0.4V) = 12.8mW

Total Power Dissipation per output pair = Pd_H + Pd_L = 32mW

Q1

V

OUT

V

DDO

RL

50

V