85210AY-31 www.idt.com REV. C JULY 10, 2012
10
ICS85210-31
LOW SKEW, DUAL, 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 4.
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
OH_MIN
/R
L
) * (V
DDO_MAX
- V
OH_MIN
)
Pd_L = (V
OL_MAX
/R
L
) * (V
DDO_MAX
- V
OL_MAX
)
Pd_H = (1V/50Ω) * (2V - 1V) = 20mW
Pd_L = (0.4V/50Ω) * (2V - 0.4V) = 12.8mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 32.8mW
FIGURE 4. HSTL DRIVER CIRCUIT AND TERMINATION
V
DDO
V
OUT
RL
50
:
Q1
