Xilinx RocketIO User Manual page 108

R
2
V > 3VDC
IN
IN
1
SHDN
5
+
SENSE
10µF
LT1963
GNDA
Figure 3-7: Power Supply Circuit Using LT1963 (LT1963A) Regulator
The required voltage regulator is the Linear Technology LT1963 (LT1963A) (or LT1964) device or
equivalent. The regulator must be used in the circuit specified by the manufacturer.
shows the schematic for the adjustable version of the LT1963 (LT1963A) device with values for a
2.5 V supply, as would be used for AVCCAUXRX and AVCCAUXTX. Alternatively, fixed output
voltage devices in the same series may be used, such as the LT1963-2.5. If the fixed version is used,
SENSE should be connected to OUT.
More information on the following required voltage regulators can be obtained from:
•
•
•
•
All characterization work was done using the LT1963 (LT1963A) device. If another part is used
instead of the LT1963 (LT1963A), it must meet the following requirements:
•
•
•
Termination voltages V
where the RocketIO transceiver is interfacing with a transceiver from another vendor, termination
voltage may be dictated by the specifications of the other transceiver. In cases where the RocketIO
transceiver is interfacing with another RocketIO transceiver, any termination voltage my be used.
With AVCCAUXTX and AVCCAUXRX already powered with 2.5V, an obvious choice for VTTX
and VTRX is 2.5V. However, it should be noted that when AC coupling is used, the optimum value
for VTRX is 1.7V.
The LT1963 (LT1963A) circuit's output capacitors (330 µF and 1 µF) may be placed anywhere on
the board, preferably close to the output of the LT1963 (LT1963A) device.
Refer to the manufacturer's Web page at
this device.
108
4
OUT
3
GND
+
TAB
1µF
330µF
93.8Ω
Linear Technology LT1963 (LT1963A) 1.5A low-dropout (LDO) (For more information about
this device, visit http://www.linear-tech.com/prod/datasheet.html?datasheet=886.)
Texas Instruments TPS795xx 500mA RF LDO (For more information about this device, visit
http://focus.ti.com/docs/prod/productfolder.jhtml?genericPartNumber=TPS79518.)
Texas Instruments TPS796xx 1A RF LDO (For more information about this device, visit
http://focus.ti.com/docs/prod/productfolder.jhtml?genericPartNumber=TPS79618.)
Texas Instruments TPS786xx 1.5A RF LDO (For more information about this device, visit
http://focus.ti.com/docs/prod/productfolder.jhtml?genericPartNumber=TPS78618.)
Must be a linear regulator.
Must have output noise no greater than 40 µV RMS from 10 Hz to 100 KHz.
Must regulate to within 2% of the nominal output voltage (±50 mV).
and V
TTX
www.xilinx.com
1-800-255-7778
Chapter 3: Analog Design Considerations
1µF 1µF 1µF 1µF 1µF
may be of any value in the range of 1.8 V to 2.625 V. In cases
TRX
http://www.linear-tech.com
2.5V@1.5A
1µF 1µF 1µF 1µF
UG024_026_120202
Figure 3-7
for further information about
RocketIO™ Transceiver User Guide
UG024 (v2.3.2) June 24, 2004
GNDA