ICS8530FY-01 REVISION G NOVEMBER 15, 2012

12

©2012 Integrated Device Technology, Inc.

ICS8530-01 Data Sheet

LOW SKEW, 1-TO-16, DIFFERENTIAL-TO-3.3V LVPECL FANOUT BUFFER

3. Calculations and Equations.

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

LVPECL output driver circuit and termination are shown in Figure 4.

Figure 4. LVPECL Driver Circuit and Termination

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

VCCO – 2V.

•

For logic high, VOUT = VOH_MAX = VCCO_MAX – 0.9V

(VCCO_MAX – VOH_MAX) = 0.9V

•

For logic low, VOUT = VOL_MAX = VCCO_MAX – 1.7V

(VCCO_MAX – VOL_MAX) = 1.7V

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 – 0.9V)/50

] * 0.9V = 19.8mW

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

[(2V – 1.7V)/50

] * 1.7V = 10.2mW

Total Power Dissipation per output pair = Pd_H + Pd_L = 30mW

V

OUT

V

CCO

V

CCO - 2V

Q1

RL

50

Ω