ICS85322I Data Sheet DUAL LVCMOS/LVTTL-TO-DIFFERENTIAL 2.5V/3.3V LVPECL TRANSLATOR
ICS85322I REVISION D MARCH 6, 2014 10 ©2014 Integrated Device Technology, Inc.
3. Calculations and Equations.
The purpose of this section is to calculate the power dissipation at the output(s).
LVPECL output driver circuit and termination are shown in Figure 3.
Figure 3. LVPECL Driver Circuit and Termination
To calculate worst case power dissipation at the output(s), use the following equations which assume a 50 load, and a termination voltage of
V
CC
–2V.
• For logic high, V
OUT
=V
OH_MAX
= V
CC_MAX
– 0.9V
(V
CC_MAX
–V
OH_MAX
) = 0.9V
• For logic low, V
OUT
=V
OL_MAX
= V
CC_MAX
– 1.7V
(V
CC_MAX
–V
OL_MAX
)=1.7V
Pd_H is the power dissipation when the output drives high.
Pd_L is the power dissipation when the output drives low.
Pd_H = [(V
OH_MAX
–(V
CC_MAX
– 2V))/R
L
]*(V
CC_MAX
–V
OH_MAX
)
=[(2V–(V
CC_MAX
–V
OH_MAX
))/R
L
]*(V
CC_MAX
–V
OH_MAX
)
= [(2V – 0.9V)/50] * 0.9V = 19.8mW
Pd_L = [(V
OL_MAX
–(V
CC_MAX
– 2V))/R
L
]*(V
CC_MAX
–V
OL_MAX
)
=[(2V–(V
CC_MAX
–V
OL_MAX
))/R
L
]*(V
CC_MAX
–V
OL_MAX
)
= [(2V – 1.7V)/50] * 1.7V = 10.2mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 30mW
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