Termination Voltage - Xilinx RocketIO User Manual

Product Not Recommended for New Designs
R
Table 3-6: Qualified Linear Regulators
Linear
Technology
Linear
Technology
Texas
Instruments
Texas
Instruments
Texas
Instruments
National
Semiconductor
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
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.
V
IN
+
10μF
GND
Figure 3-7: Power Supply Circuit Using Approved 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
110
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)
Vendor Part Number
LT1963
LT1764
TPS795xx
TPS796xx
TPS786xx
LP3875
IN OUT
+
330μF
GND
www.xilinx.com
Chapter 3: Analog Design Considerations
Current Rating
1.5A
3.0A
0.5A
1.0A
1.5A
1.5A
1μF 1μF 1μF 1μF 1μF 1μF
RocketIO™ Transceiver User Guide
Description
Low-Noise LDO Regulator
Low Noise LDO Regulator
RF LDO Regulator
RF LDO Regulator
RF LDO Regulator
Ultra LDO Regulator
Figure 3-7. The
V @1.5A
OUT
1μF 1μF
GND
UG024_026_080404
UG024 (v3.0) February 22, 2007