ICS85314I-11 Datasheet, PDF (13/18 Pages) Integrated Circuit Systems – LOW SKEW, 1-TO-5 DIFFERENTIAL-TO-2.5V/3.3V LVPECL FANOUT BUFFER

Integrated
Circuit
Systems, Inc.
ICS85314I-11
LOW SKEW, 1-TO-5
DIFFERENTIAL-TO-2.5V/3.3V LVPECL FANOUT BUFFER
3. Calculations and Equations.
LVPECL output driver circuit and termination are shown in Figure 6.
V
CC
Q1
V_OUT
RL
50
V_CC - 2V
FIGURE 6. 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
– 1.0V
OUT
OH_MAX
CC_MAX
(V
- V ⁾ = 1.0V
CC_MAX OH_MAX
• For logic low, V = V = V – 1.7V
OUT
OL_MAX
CC_MAX
(V
- V ⁾ = 1.7V
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 - 1V)/50Ω] * 1V = 20.0mW
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 - 1.7V)/50Ω] * 1.7V = 10.2mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 30.2mW
85314AGI-11
www.icst.com/products/hiperclocks.html
13
REV. C MAY 24, 2005