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ICS8732-01 Datasheet, PDF (12/17 Pages) Integrated Device Technology – Maximum output frequency | |||
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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 6.
ICS8732-01
LOW VOLTAGE, LOW SKEW
3.3V LVPECL CLOCK GENERATOR
VCCO
Q1
V
OUT
RL
50
VCCO - 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.
CCO
⢠For logic high, V = V
=V
â 0.9V
OUT
OH_MAX
CCO_MAX
(V
- V ) = 0.9V
CCO_MAX OH_MAX
⢠For logic low, V = V = V
â 1.7V
OUT
OL_MAX
CCO_MAX
(V
- V ) = 1.7V
CCO_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 â (V
- 2V))/R ] * (V
- V ) = [(2V - (V
- V ))/R ] * (V
-V )=
OH_MAX
CCO_MAX
L
CCO_MAX OH_MAX
CCO_MAX OH_MAX
L
CCO_MAX OH_MAX
[(2V - 0.9V)/50Ω] * 0.9V = 19.8mW
Pd_L = [(V â (V
- 2V))/R ] * (V
- V ) = [(2V - (V
- V ))/R ] * (V
-V )=
OL_MAX
CCO_MAX
L
CCO_MAX OL_MAX
CCO_MAX OL_MAX
L
CCO_MAX OL_MAX
[(2V - 1.7V)/50Ω] * 1.7V = 10.2mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 30mW
8732AY-01
www.idt.com
12
REV. E MAY 2, 2013
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