Xilinx RocketIO User Manual

110 www.xilinx.com RocketIO™ Transceiver User Guide
UG024 (v3.0) February 22, 2007
Chapter 3: Analog Design Considerations
R
♦ Output noise no greater than 40 μV RMS from 10 Hz to 100 kHz
♦ Regulation to within 2% of nominal output voltage (± 50 mV for 2.5V supply)
Voltage regulators in this category typically are available in both fixed and adjustable
output varieties. Those with fixed output voltage require no output adjustment resistors,
whereas adjustable versions require a two resistor voltage divider to determine the output
voltage. See vendor data to select these resistors and for information on connection of all
other regulator pins (Sense, Shutdown, etc.).
Vendor application examples typically recommend a 10 μF capacitor on the input and a
10 μF capacitor on the output of the regulator. For use with RocketIO transceivers, Xilinx
requires that this be modified according to the capacitor topology shown in Figure 3-7. The
10 μF capacitor on the input is not changed. However, the 10 μF output capacitor is
replaced with one 330 μF capacitor and eight 1.0 μF capacitors. In cases where more than
16 MGTs are powered from a single regulator, an additional 1.0 μF capacitor is required for
every two additional MGTs. Tantalum is the recommended capacitor type for the 330 μF
capacitor, though the low-ESR electrolytic type is also acceptable. X7R or X5R ceramic is
the recommended capacitor type for the 1.0 μF and 10 μF capacitors. These capacitors can
be placed anywhere on the board, but preferably in close proximity to the regulator.
Termination Voltage
Termination voltages VTTX and VTRX can be of any value in the range of 1.8V to 2.625V
(VTTX) or 1.6V to 2.525 V (VTRX). In cases where the RocketIO transceiver is interfacing
Table 3-6: Qualified Linear Regulators
Vendor Part Number Current Rating Description
Linear
Technology
LT1963 1.5A Low-Noise LDO Regulator
Linear
Technology
LT1764 3.0A Low Noise LDO Regulator
Texas
Instruments
TPS795xx 0.5A RF LDO Regulator
Texas
Instruments
TPS796xx 1.0A RF LDO Regulator
Texas
Instruments
TPS786xx 1.5A RF LDO Regulator
National
Semiconductor
LP3875 1.5A Ultra LDO Regulator
Figure 3-7: Power Supply Circuit Using Approved Regulator
UG024_026_080404
IN
V
IN
OUT
GND
10μF
+
330μF
+
1μF 1μF 1μF 1μF
V @1.5A
GND
1μF 1μF1μF 1μF
GND
OUT
Product Not Recommended for New Designs

Xilinx RocketIO Specifications

General

Brand	Xilinx
Model	RocketIO
Category	Transceiver
Language	English