TLK2701

The TLK2701 is housed in a high-performance, thermally enhanced, 64-pin VQFP (RCP64) 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 to 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 PFP PowerPAD package is 8 mm X 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.

Other requirements for thermal lands and thermal vias are detailed in the TI application note PowerPAD Thermally Enhanced Package Application Report, TI literature number SLMA002, available via the TI Web pages beginning at URL: http://www.ti.com.

For the TLK2701, this thermal land should be grounded to the low-impedance ground plane of the device. This improves not only thermal performance but also the electrical grounding of the device. It is also recommended that the device ground terminal landing pads be connected directly to the grounded thermal land. The land size should be as large as possible without shorting device signal terminals. The thermal land may be soldered to the exposed PowerPAD using standard reflow soldering techniques.

While the thermal land may be electrically floated and configured to remove heat to an external heat sink, it is recommended that the thermal land be connected to the low impedance ground plane for the device. More information may be obtained from the TI application note PHY Layout, TI literature number SLLA020.

The TLK2701 is a member of the transceiver family of multigigabit transceivers used in ultrahigh-speed bidirectional point-to-point data transmission systems. The TLK2701 supports an effective serial interface speed of 1.5 Gbps to 2.5 Gbps, providing up to 2 Gbps of data bandwidth. The TLK2701 is pin-for-pin compatible with the TLK2500. The TLK2701 is both pin-for-pin compatible with and functionally identical to the TLK1501, a 0.6 to 1.5 Gbps transceiver, and the TLK3101, a 2.5 to 3.125 Gbps transceiver, providing a wide range of performance solutions with no required board layout changes.

The primary application of this chip of the TLK2701 is to provide very high-speed I/O data channels for point-to-point baseband data transmission over controlled impedance media of approximately 50.The transmission media can be printed-circuit board, copper cables, or fiber-optic cable. The maximum rate and distance of data transfer is dependent upon the attenuation characteristics of the media and the noise coupling to the environment.

This TLK2701 can also be used to replace parallel data transmission architectures by providing a reduction in the number of traces, connector terminals, and transmit/receive terminals. Parallel data loaded into the transmitter is delivered to the receiver over a serial channel, which can be a coaxial copper cable, a controlled impedance backplane, or an optical link. It is then reconstructed into its original parallel format. It offers significant power and cost savings over current solutions, as well as scalability for higher data rate in the future.

The TLK2701 performs data conversion parallel-to-serial and serial-to-parallel. The clock extraction functions as a physical layer interface device. The serial transceiver interface operates at a maximum speed of 2.5 Gbps. The transmitter latches 16-bit parallel data at a rate based on the supplied reference clock (GTX_CLK). The 16-bit parallel data is internally encoded into 20 bits using an 8-bit/10-bit (8B/10B) encoding format. The resulting 20-bit word is then transmitted differentially at 20 times the reference clock (GTX_CLK) rate. The receiver section performs the serial-to-parallel conversion on the input data, synchronizing the resulting 20-bit wide parallel data to the extracted reference clock (RX_CLK). It then decodes the 20 bit wide data using 8-bit/10-bit decoding format resulting in 16 bits of parallel data at the receive data terminals (RXD0-15). The outcome is an effective data payload of 1.20 Gbps to 2.0 Gbps (16 bits data x the GTX_CLK frequency).

The TLK2701 is housed in a high performance, thermally enhanced, 64-pin VQFP PowerPAD package. Use of the PowerPAD package does not require any special considerations except to note that the PowerPAD, which has an exposed die pad on the bottom of the device, is a metallic thermal and electrical conductor. It is recommended that the TLK2701 PowerPAD is soldered to the thermal land on the board. All ac performance specifications in this data sheet are measured with the PowerPAD soldered to the test board.

The TLK2701 provides an internal loopback capability for self-test purposes. Serial data from the serializer is passed directly to the deserializer, allowing the protocol device a functional self-check of the physical interface.

The TLK2701 is designed to be hot plug capable. An on-chip power-on reset circuit holds the RX_CLK low during power up. This circuit also holds the parallel side output signal terminals as well as DOUTTXP and DOUTTXN in a high-impedance state during power up.

The TLK2701 has a loss of signal detection circuit for conditions where the incoming signal no longer has a sufficient voltage amplitude to keep the clock recovery circuit in lock.

To prevent a data bit error from causing a data packet from being interpreted as a comma and thus causing the erroneous word alignment by the comma detection circuit, the comma word alignment circuit is turned off after the link is properly established in TLK2701.

The TLK2701 allows users to implement redundant ports by connecting receive data bus terminals from two TLK2701 devices together. Asserting the LCKREFN to go to a low state causes the receive data bus terminals, RXD[0:15], RX_CLK and RX_ER, RX_DV/LOS to go to a high-impedance state. This places the device in a transmit-only mode since the receiver is not tracking the data.

The TLK2701 uses a 2.5-V supply. The I/O section is 3 V compatible. With the 2.5-V supply the chipset is very power-efficient, consuming less than 360 mW typically. The TLK2701 is characterized for operation from ?40°C to 85°C.