TLK1521 Datasheet, PDF (16/19 Pages) Texas Instruments – 500 Mbps to 1.3 Gbps TRANSCEIVER

TLK1521
500 Mbps to 1.3 Gbps TRANSCEIVER
SLLS591A− OCTOBER 2003 − REVISED JANUARY 2004
TXP
RXP
ZO
TXN
Transmitter
ZO
Media
VDD
ZO
5 kΩ
+
_
ZO
7.5 kΩ
GND
RXN
Receiver
Figure 11. High-Speed I/O Directly Coupled Mode
TXP
RXP
ZO
TXN
Transmitter
ZO
Media
VDD
ZO
5 kΩ
+
_
ZO
7.5 kΩ
GND
RXN
Receiver
Figure 12. High-Speed I/O AC-Coupled Mode
AC-coupling is only recommended if the parallel TX data stream is encoded to achieve a dc-balanced data
stream. Otherwise, the ac-capicitors can induce common-mode voltage drift due to the dc-unbalanced data
stream.
designing with PowerPAD
The TLK1521 is housed in a high-performance, thermally enhanced, 64-pin HTQFP (PAP64) PowerPAD
package. Use of the PowerPAD package does not require any special considerations except to note that the
PowerPAD, which is an exposed die pad on the bottom of the device, is a metallic, thermal, and electrical
conductor. Therefore, if not implementing PowerPAD PCB features, the use of solder masks (or other assembly
techniques) may be required to prevent any inadvertent shorting by the exposed PowerPAD of connection
etches or vias under the package. It is strongly recommended that the PowerPAD be soldered to the
thermal land. The recommended convention, however, is to not run any etches or signal vias under the device,
but to have only a grounded thermal land as explained below. Although the actual size of the exposed die pad
may vary, the minimum size required for the keep out area for the 64-pin PAP PowerPAD package is 8 mm ×
8 mm.
It is recommended that there be a thermal land, which is an area of solder-tinned-copper, underneath the
PowerPAD package. The thermal land varies in size depending on the PowerPAD package being used, the PCB
construction, and the amount of heat that needs to be removed. In addition, the thermal land may or may not
contain numerous thermal vias depending on PCB construction.
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