ICS85222 Datasheet, PDF (8/12 Pages) Integrated Circuit Systems – DUAL LVCMOS / LVTTL-TO DIFFERENTIAL LVHSTL TRANSLATOR

Integrated
Circuit
Systems, Inc.
ICS85222
DUAL LVCMOS / LVTTL-TO-
DIFFERENTIAL LVHSTL TRANSLATOR
3. Calculations and Equations.
The purpose of this section is to derive the power dissipated into the load.
LVHSTL output driver circuit and termination are shown in Figure 2.
V_DD
Q1
V_OUT
RL
50Ω
FIGURE 2. LVHSTL DRIVER CIRCUIT AND TERMINATION
To calculate worst case power dissipation into the load, use the following equations which assume a 50Ω load.
Pd_H is power dissipation when the output drives high.
Pd_L is the power dissipation when the output drives low.
Pd_H = (V
/R ) * (V
-V
)
OH_MAX L
DD_MAX OH_MAX
Pd_L = (V
/R ) * (V
-V )
OL_MAX L
DD_MAX OL_MAX
Pd_H = (1.2V/50Ω) * (3.465V - 1.2V) = 54.4mW
Pd_L = (0.4V/50Ω) * (3.465V - 0.4V) = 24.52mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 78.9mW
85222AM
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8
REV. B MARCH 31, 2005