R31DS0036EU0300 MAY 20, 2021

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©2021 Renesas Electronics Corporation

8SLVP1212 Datasheet

3. Calculations and Equations.

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

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

Figure 8. LVPECL Driver Circuit and Termination

To calculate power dissipation per output pair due to loading, use the following equations which assume a 50 load,

and a termination voltage of VCC – 2V.

•

For logic high, VOUT = VOH_MAX = VCC_MAX – 0.6V

(VCC_MAX – VOH_MAX) = 0.6V

•

For logic low, VOUT = VOL_MAX = VCC_MAX – 1.28V

(VCC_MAX – VOL_MAX) = 1.28V

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 – (VCC_MAX – 2V))/RL] * (VCC_MAX – VOH_MAX) = [(2V - (VCC_MAX – VOH_MAX))/RL] * (VCC_MAX – VOH_MAX) =

[(2V – 0.6V)/50] * 0.6V =

16.8mW

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

[(2V – 1.28V)/50] * 1.28V =

18.4mW

Total Power Dissipation per output pair = Pd_H + Pd_L =

35.2mW

V

OUT

V

CC

V

CC - 2V

Q1

RL