8S89874BKILF IDT [Integrated Device Technology], 8S89874BKILF Datasheet - Page 15

• Manufacturer Part Number: 8S89874BKILF
• Description: 1:2 Differential-to-LVPECL Buffer/Divider
• Manufacturer: IDT [Integrated Device Technology]

ICS8S89874I Data Sheet
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 7.
Figure 7. LVPECL Driver Circuit and Termination
T
V
Pd_H is power dissipation when the output drives high.
Pd_L is the power dissipation when the output drives low.
Pd_H = [(V
[(2V – 0.82V)/50Ω] * 0.82V = 19.35mW
Pd_L = [(V
[(2V – 1.58V)/50Ω] * 1.58V = 13.27mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 32.62mW
ICS8S89874BKI REVISION A OCTOBER 22, 2010
o calculate worst case power dissipation into the load, use the following equations which assume a 50Ω load, and a termination voltage of
CC
•
•
– 2V.
For logic high, V
(V
For logic low, V
(V
OL_MAX
OH_MAX
CC_MAX
CC_MAX
– (V
– (V
– V
– V
CC_MAX
OH_MAX
OL_MAX
CC_MAX
OUT
OUT
Q1
= V
= V
) = 1.58V
) = 0.82V
V
– 2V))/R
– 2V))/R
CC
OL_MAX
OH_MAX
L
L
= V
] * (V
] * (V
= V
CC_MAX
CC_MAX
CC_MAX
CC_MAX
RL
50Ω
V
– 1.58V
CC
V
– 0.82V
– V
– V
OUT
- 2V
OL_MAX
OH_MAX
) = [(2V – (V
) = [(2V – (V
15
CC_MAX
CC_MAX
– V
– V
OL_MAX
OH_MAX
))/R
))/R
1:2 DIFFERENTIAL-TO-LVPECL BUFFER/DIVIDER
L
L
] * (V
] * (V
CO_MAX
©2010 Integrated Device Technology, Inc.
CC_MAX
– V
– V
OL_MAX
OH_MAX
) =
) =