ICS873033 Datasheet, PDF (12/16 Pages) Integrated Circuit Systems – HIGH SPEED, ÷4 DIFFERENTIAL-TO- 3.3V, 5V LVPECL/ECL CLOCK GENERATOR

Integrated
Circuit
Systems, Inc.
ICS873033
HIGH SPEED, ÷4 DIFFERENTIAL-TO-
3.3V, 5V LVPECL/ECL CLOCK GENERATOR
3. Calculations and Equations.
The purpose of this section is to derive the power dissipated into the load.
LVPECL output driver circuit and termination are shown in Figure 7.
VCC
Q1
VOUT
RL
50
VCC - 2V
FIGURE 7. LVPECL DRIVER CIRCUIT AND TERMINATION
To calculate worst case power dissipation into the load, use the following equations which assume a 50Ω load, and a termination
voltage of V - 2V.
CC
• For logic high, V = V
=V
–0.935V
OUT
OH_MAX
CC_MAX
(V
- V ⁾ = 0.935V
CC_MAX OH_MAX
• For logic low, V = V
=V
– 1.67V
OUT
OL_MAX
CC_MAX
(V
- V ⁾ = 1.67V
CC_MAX OL_MAX
Pd_H is power dissipation when the output drives high.
Pd_L is the power dissipation when the output drives low.
Pd_H = [(V
– (V - 2V))/R ] * (V - V ) = [(2V - (V
- V ^))/R ] * (V - V ) =
OH_MAX
CC_MAX
L
CC_MAX OH_MAX
CC_MAX OH_MAX
L
CC_MAX OH_MAX
[(2V - 0.935V)/50Ω] * 0.935V = 19.92mW
Pd_L = [(V – (V - 2V))/R ] * (V
- V ) = [(2V - (V
- V ^))/R ] * (V - V ) =
OL_MAX
CC_MAX
L
CC_MAX OL_MAX
CC_MAX OL_MAX
L
CC_MAX OL_MAX
[(2V - 1.67V)/50Ω] * 1.67V = 11.02mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 30.94mW
873033AM
www.icst.com/products/hiperclocks.html
12
REV. A OCTOBER 19, 2005