Datasheet

AD8153
Rev. 0 | Page 21 of 24
OUTPUT COMPLIANCE
Figure 40 is a graphical depiction of the single-ended waveform
at the output of the AD8153. The common-mode level (V
OCM
)
and the amplitude (V
OSE
) of this waveform are a function of the
output tail current (I
T
), the output termination supply voltage
(V
TTO
), the topology of the far-end receiver, and whether ac- or
dc-coupling is used. Keep in mind that the output tail current
varies with the pre-emphasis level. The user must ensure that
the high (V
H
) and low (V
L
) voltage excursions at the output are
within the single-ended absolute voltage range limits as
specified in
Tabl e 1. Failure to understand the implications of
output signal levels and the choice of ac- or dc-coupling may
lead to transistor saturation and poor transmitter performance.
Tabl e 9 shows an example calculation of the output levels for the
typical case, where V
CC
= V
TTO
= 3.3 V, with 50 Ω far-end
terminations to a 3.3 V supply.
06393-012
V
OCM
V
H
V
L
V
OSE-DC
V
OSE-BOOST
V
TTO
~320ps
Figure 40. Single-Ended Output Waveform
Table 9. Output Voltage Levels
DC-Coupled AC-Coupled
PE Setting I
T
(mA) V
OSE-DC
(mV p-p) V
OSE-BOOST
(mV p-p) V
OCM
(V) V
H
(V) V
L
(V) V
OCM
(V) V
H
(V) V
L
(V)
0 16 400 400 3.1 3.3 2.9 2.9 3.1 2.7
1 20 400 500 3.05 3.3 2.8 2.8 3.05 2.55
2 24 400 600 3 3.3 2.7 2.7 3 2.4
3 28 400 700 2.95 3.3 2.6 2.6 2.95 2.25
Table 10. Symbol Definitions
Symbol Formula Definition
V
OSE-DC
Ω×
=
25
0PE
T
I
Single-ended output voltage swing after settling
V
OSE-BOOST
Ω× 25
T
I
Boosted single-ended output voltage swing
V
OCM
(dc-coupled)
Ω×− 25
2
T
TTO
I
V
Common-mode voltage when the output is dc-coupled
V
OCM
(ac-coupled)
Ω×− 50
2
T
TTO
I
V
Common-mode voltage when the output is ac-coupled
V
H
V
OCM
+ V
OSE-BOOST
/2
High single-ended output voltage excursion
V
L
V
OCM
- V
OSE-BOOST
/2
Low single-ended output voltage excursion