ICS853014 Datasheet, PDF (13/17 Pages) Integrated Circuit Systems – LOW SKEW, 1-TO-5 2.5V/3.3V DIFFERENTIAL-TO-LVPECL/ECL FANOUT BUFFER

Integrated
Circuit
Systems, Inc.
ICS853014
LOW SKEW, 1-TO-5
2.5V/3.3V DIFFERENTIAL-TO-LVPECL/ECL FANOUT BUFFER
3. Calculations and Equations.
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 = 11.2mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 30.94mW
853014BG
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13
REV. C MAY 13, 2005