ICS85222-01 Datasheet, PDF (9/13 Pages) Integrated Circuit Systems – DUAL LVCMOS / LVTTL-TO DIFFERENTIAL

Integrated
Circuit
Systems, Inc.
3. Calculations and Equations.
The purpose of this section is to derive the power dissipated into the load.
HSTL output driver circuit and termination are shown in Figure 3.
ICS85222-01
DUAL LVCMOS / LVTTL-TO-
DIFFERENTIAL HSTL TRANSLATOR
V_DD
Q1
V_OUT
RL
50Ω
FIGURE 3. HSTL 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 = (1.4V/50Ω) * (3.465V - 1.4V) = 57.82mW
Pd_L = (0.4V/50Ω) * (3.465V - 0.4V) = 24.52mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 82.34mW
85222AM-01
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9
REV. A NOVEMBER 15, 2005