ICS85214I Datasheet, PDF (11/15 Pages) Integrated Circuit Systems – LOW SKEW, 1-TO-5 DIFFERENTIAL-TO-HSTL FANOUT BUFFER

Integrated
Circuit
Systems, Inc.
ICS85214I
LOW SKEW, 1-TO-5
DIFFERENTIAL-TO-HSTL FANOUT BUFFER
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 5.
V_DDO
Q1
V
OUT
RL
50Ω
FIGURE 5. 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_MIN L
DDO_MAX OH_MIN
Pd_L = (V /R ) * (V
-V )
OL_MAX L
DDO_MAX OL_MAX
Pd_H = (1.0V/50Ω) * (2V - 1.0V) = 20mW
Pd_L = (0.4V/50Ω) * (2V - 0.4V) = 12.8mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 32.8mW
85214AGI
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11
REV. A JUNE 1, 2005