ICS853S031I Data Sheet

LOW SKEW, 1-TO-9, DIFFERENTIAL-TO-2.5V, 3.3V LVPECL/ECL FANOUT BUFFER

ICS853S031BYI REVISION A AUGUST 17, 2011

16

©2011 Integrated Device Technology, Inc.

3. Calculations and Equations.

The purpose of this section is to calculate power dissipation on the LVPECL output pairs.

LVPECL output driver circuit and termination are shown in Figure 8.

Figure 8. LVPECL Driver Circuit and Termination

To calculate typical case power dissipation into the load, use the following equations which assume a 50Ω load, and a termination voltage of

VCCO – 2V.

•

For logic high, VOUT = VOH_MAX = VCCO_MAX – 0.71V

(VCCO_MAX – VOH_MAX) = 0.71V

•

For logic low, VOUT = VOL_MAX = VCCO_MAX – 1.48V

(VCCO_MAX – VOL_MAX) = 1.48V

Pd_H is power dissipation when the output drives high.

Pd_L is the power dissipation when the output drives low.

Pd_H = [(VOH_MAX – (VCCO_MAX – 2V))/RL] * (VCCO_MAX – VOH_MAX) = [(2V – (VCCO_MAX – VOH_MAX))/RL] * (VCCO_MAX – VOH_MAX) =

[(2V – 0.71V)/50

Ω] * 0.71V = 18.32mW

Pd_L = [(VOL_MAX – (VCCO_MAX – 2V))/RL] * (VCCO_MAX – VOL_MAX) = [(2V – (VCCO_MAX – VOL_MAX))/RL] * (VCCO_MAX – VOL_MAX) =

[(2V – 1.48V)/50

Ω] * 1.48V = 15.39mW

Total Power Dissipation per output pair = Pd_H + Pd_L = 33.71mW

V

OUT

V

CCO

V

CCO - 2V

Q1

RL

50

Ω