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TAN-007
...the analog plus company TM
XR-T5683 Operation at 10.1 Mbps
June 1997-3
INTRODUCTION The purpose of this application note is to present an example circuit, illustrating how to operate the XR-T5683 device at 10.1 Mbps. This note shows the results of measurements made on the XR-T5683 at a 10.1 Mbps data rate. Hardware used for this evaluation was a slightly modified board designed for 8.448 Mbps E2 service. The only change to the circuit, which is shown in Figure 1, involved lowering the LC clock extraction circuit tuning capacitor value. Circuit Details LC Tank Circuit: L1 - Schott Corporation Part Number 67146440, 5H nominal, Q ~ 90 C7 - 33 pF R7 - 15 k
Note Circuit actually resonates at 10.1 MHz due to stray capacitance.
Measurement Results The oscilloscope photographs given in Figure 2 shows XR-T5683 operation at 10.1 Mbps. Photos A and B show the receive-side timing relationship between the input signals as measured at the transformer primary, the recovered clock (RCLK), and the dual-rail data (RPOS and RNEG). Photo A is for a repetitive 1010 pattern while photo B uses a pseudo-random sequence. Photo C has an expanded horizontal scale that more clearly shows the received data (RPOS) to recovered clock (RCLK) timing relationship. Photo D is the transmitter output for all ones data. The pulse amplitude shown in this picture is approximately 1V peak because the measurement was made with the output transformer secondary connected to the oscilloscope 50 input through a 75 to 50 matching pad that had 5.6 dB loss. CONCLUSION These measurements show that in the circuit tested, the XR-T5683, the Pulse Engineering transformers, and the Schott timing inductor are all functional at 10.1 Mbps.
Transformers The input and output transformers are both Pulse Engineering type PE-65835. The input unit is connected as a 1:2 step-up and the output as a 2:1 step-down.
Rev. 1.04
E1994
EXAR Corporation, 48720 Kato Road, Fremont, CA 94538 z (510) 668-7000 z FAX (510) 668-7017 1
TAN-007
SCHOTT 67146440 L1 1 R4 C3 0.1uF C7 3 C10 0.1uF C9 0.1uF + C8 22uF
VCC
GND
C4 0.1uF
6 TBIAS PE-65835 T1 10 3 8 5 6 2 R1 300 3 C2 0.1uF TPOS TX DATA TNEG INPUTS TCLK 17 12 16 TPOS TNEG TCLK 5 RXDATA+ BIAS
49 TE RVCC RPOS 11 RNEG 10 U1 RCLK 8 VCC
RPOS RX DATA RNEG OUTPUTS RCLK
RING RX INPUT TIP
RXDATA-
XR-T5683
TXDAT+ TVCC TXDAT13 18 15
PE-65835 R2 46.4 10 8 6 R3 46.4 C6 0.1uF C5 0.1uF T2 1 3 5 RING TX OUT TIP
C1 0.1uF
PDC RGND TGND 1 1 7 4
Figure 1. XR-T5683 Circuit Diagram
Rev. 1.04 2
TAN-007
Pin 10 (RNEG) Pin 11 (RPOS) Pin 8 (RCLK) Input Signal (At Input Trans. Primary) Pin 10 (RNEG) Pin 11 (RPOS) Pin 8 (RCLK) Input Signal
A. 1010 Data
B. 215 - 1 Length AMI Encoded Pseudorandom Data
Pin 11 (RPOS)
Pin 8 (RCLK)
C. 1010 Data
D. 1111 Data, Transmit Output (Transformer output measured through 5.6dB 75 to 50 Pad terminated with 50) Figure 2. XR-T5683 Operating at 10.1 Mbps
Rev. 1.04 3
TAN-007
NOTICE EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration purposes and may vary depending upon a user's specific application. While the information in this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies. EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances. Copyright 1994 EXAR Corporation Datasheet June 1997 Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
Rev. 1.04 4

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