ONET8501P-EV
11.3 GBPS RATE-SELECTABLE LIMITING AMPLIFIER EVALUATION BOARD
Version 0.4 · Revised October 2007
4
TI CONFIDENTIAL
www.ti.com
CALIBRATION LINE _________________________________________________________________
For optimum performance, the EV board is equipped
with 50
Ω
SMA connectors and well-controlled 50
Ω
impedance microstrip transmission lines in the high-
speed data-signal path. However, inevitable line loss
occurs at high frequencies.
In order to account for the resulting measurement
inaccuracies, calibration lines are provided consisting
of the same type of SMA connectors and microstrip
transmission line layout as used in the high-speed
data-signal path.
The microstrip lines are designed as 50
Ω
microstrip
lines close to the SMA connectors. Close to the chip,
the gap between the two lines of the differential pair
narrows resulting in reduced common mode
matching. The differential line impedance however is
kept constant at 100
Ω
on the entire board.
The calibration line is intended to be used for S21
and S12 calibration purposes. Furthermore, in the
time domain it helps to determine the impact of the
EV board on signal edge speed as well as
deterministic jitter.
SIGNAL PATH AND CONTROL CIRCUITRY _____________________________________________
The signal path consists of the input port SMA
connectors DIN+ and DIN-, the coupling capacitors
C14 and C19, the 50
Ω
single ended / 100
Ω
differential input transmission lines, the ONET8501P,
the 50
Ω
single ended / 100
Ω
differential output
transmission lines, the coupling capacitors C15 and
C20, and the output port SMA connectors DOUT+
and DOUT-.
The ONET8501P uses a two-wire serial interface for
digital control of the bandwidth, output amplitude,
output pre-emphasis, input threshold voltage (slice
level) and the loss of signal assert level.
Predetermined settings for bandwidth and LOS
assert levels can also be selected with the external
rate selection pins (RATE1 and RATE0). For more
information on the use of the two-wire interface,
please refer to the ONET8501P data sheet.
The ONET8501P-EV is set-up for full control and
monitoring through the two-wire interface. Manual
control of such features as external rate selection
and output disable can be done by cutting traces at
the appropriate points and using jumpers.