TAN-046 Application Note - XRT73L04 4-Channel DS3/E3/STS-1 LIU IC Power Conditioning Requirements May 23, 2001 Revision 1.03 XRT73L04 4-Channel DS3/E3/STS-1 LIU Power Conditioning Requirements 1.0 OVERVIEW XRT73L04 is a 4-Channel DS3/E3/STS-1 Transceiver (Line Interface Unit) that is designed for use in multi-standard Networking and Transmission Systems. The XRT73L04 device is a mixed signal device that supports the transmission and reception of data at the DS3, E3 and STS-1 rates. Hence, this chip handles both digital input and output signals (which switch at very fast rate and generate a lot of electrical and radio frequency noise). Additionally, this chip also consists of four independent sensitive analog receivers. As a consequence, the user must be careful in how to handle the VDD and GND pins, in order to ensure good performance of the XRT73L04 device. In particular, the user's PCB layout and handling of the VDD and GND signals must accomplish the following: 1. 2. 3. 4. It must provide good isolation between the Transmit and Receive signals. It must provide good isolation between Analog and Digital signals. It must provide good isolation between each of the four (4) Channels within the LIU IC It must provide good isolation between signals from other components on the board. In many networking or transmission systems the source of power is a DC-DC converter, which uses a switching converter to transform a -48VDC input to a +3.3VDC output. The switching converter typically uses a switching frequency from 20KHz to 1MHz and the 3.3VDC power normally carries a significant amount of `ripple' noise at this switching frequency. This ripple noise can adversely affect performance of analog circuits in the mixed signal devices (XRT73L04 and similar). This application note presents some guidelines on how to layout and filter the VDD and GND signals that are fed to the XRT73L04 device. 2.0 XRT73L04 `GND' PINS Tie all XRT73L04 `GND' pins (pin numbers 6, 15, 18, 19, 22, 31, 49, 50, 56, 62, 63, 81, 89, 92, 100, 109, 112, 118, 124, 129 and 132) to the system ground plane. In case there are separate analog and digital ground planes are available, tie all `GND' pins to the 1 TAN-046 Application Note - XRT73L04 4-Channel DS3/E3/STS-1 LIU IC Power Conditioning Requirements May 23, 2001 Revision 1.03 analog ground. Do not insert any impedance (an inductor or ferrite bead) between analog and digital ground pins of XRT73L04. 3.0 XRT73L04 `POWER' PINS The XRT73L04 device has 17 power supply pins. Pins 78, 86, 95, and 103 are the receive analog section power supply pins. Pins 4, 10, 13, 24, 27, 33, 47 and 134 are the transmit analog section power supply pins. Finally, pins 51, 58, 122 and 128 are digital power supplies. The receive analog power supply pins (pins 78, 86, 95 and 103) are the most critical as they power the four (4) clock recovery phase-lock-loops and therefore power to these pins should be as clean as possible. It is also desirable to keep the transmit power supply noise isolated from the receive power supply. Further, it is also desirable to keep the individual channels (within a given XRT73L04 device) isolated from each other. Finally, if multiple XRT73L04 devices are used in a system it is further desirable to keep their power isolated (from each other) in order to minimize cross-talk. The attached schematic (Figure 1) illustrates Exar's recommendations on how to connect the Analog and Digital VDD pins (of a single XRT73L04 device) to a 3.3V Power Supply. Exar's approach recommends the use of two-stage LC filtering. 3.1 STAGE 1 - A LARGE LC FILTER (consisting of L1 and C1) This particular LC filter consists of a 15uH inductor and a 33uF capacitor. The purpose of this LC filter is to eliminate much of the "DC-to-DC Converter-induced" low frequency ripple, within the 3.3V power supply line, prior to being routed to any of the VDD pins of the XRT73L04 device. NOTES ABOUT THIS LC FILTER: 1. This LC filter should be placed close to the output of the DC-to-DC Converter. 2. Only one such LC filter is needed, per board (even in multi-channel applications). However, multi-channel designs may have to use multiple instantiations of this LC filter due to large voltage drops across the inductor (due to the increased amount of current draw of multiple XRT73L04 devices and the dc resistance of the inductor), or because of the maximum operating current limit of this inductor as well. 3. This LC filter may not be necessary if the 3.3V Power Supply is already filtered elsewhere in the system. 2 TAN-046 Application Note - XRT73L04 4-Channel DS3/E3/STS-1 LIU IC Power Conditioning Requirements May 23, 2001 Revision 1.03 COMPONENT SELECTION FOR L1 AND C1 The XRT73L04 device draws about 470mA of current. We recommend that the user select a High Current Inductor, that has a small enough DC resistance such that the voltage drop across the inductor will not exceed 50mV. Therefore, the user should select a 15uH Inductor that has a DC resistance of less than 0.106. An example of an acceptable inductor for L1 is the 4922-15L from API-Delevan. This particular inductor has a maximum dc resistance of 0.089, and has a maximum current rating of 2.11A. Contact information for API-Delevan is presented in Appendix A, at the end of this Applications Note. The capacitor, C1, should be a 33uF 10V Tantalum capacitor, which is supplied by various manufacturers. Digikey PCT2336CT-ND or equivalent would be acceptable. 3.2 STAGE 2 - SMALLER LC FILTERING FOR RECEIVE AND TRANSMIT ANALOG VDD PINS After the Power Supply signal passes through the large LC filter (consisting of L1 and C1), it should then be routed to nine different points, in parallel (in order to support each of the four channels). * Directly to the Digital VDD pins of the XRT73L04 device. * To an LC filter (consisting of L2 and C2), prior to being routed to the Receive Analog VDD pin of Channel 0 (pin 78). * To an LC filter (consisting of L3 and C3), prior to being routed to the Transmit Analog VDD pins of Channel 0 (pins 33 and 47). * To an LC filter (consisting of L4 and C4), prior to being routed to the Receive Analog VDD pin of Channel 1 (pin 86). * To an LC filter (consisting of L5 and C5), prior to being routed to the Transmit Analog VDD pins of Channel 1 (pins 24 and 27). * To an LC filter (consisting of L6 and C6), prior to being routed to the Receive Analog VDD pin of Channel 2 (pin 103). * To an LC filter (consisting of L7 and C7), prior to being routed to the Transmit Analog VDD pins of Channel 2 (pins 4 and 134). * To an LC filter (consisting of L8 and C8), prior to being routed to the Receive Analog VDD pin of Channel 3 (pin 95). 3 TAN-046 Application Note - XRT73L04 4-Channel DS3/E3/STS-1 LIU IC Power Conditioning Requirements May 23, 2001 Revision 1.03 * To an LC filter (consisting of L9 and C9), prior to being routed to the Transmit Analog VDD pins of Channel 3 (pins 13 and 10). The purpose of this LC filter is three-fold: 1. To provide some isolation and filtering between the Digital VDD line and the Analog VDD lines. 2. To provide some isolation (and reduce cross-talk) between the Transmit and Receive Analog VDD lines. 3. To provide some isolation (and reduce cross-talk) between each of the four channels within the XRT73L04 device. NOTE: In contrast to the LC filter (consisting of Inductor L1 and Capacitor C1), these LC filters must not be shared with other Channels or LIU Devices. COMPONENT SELECTION FOR L2 - L9 AND C2 - C9 As mentioned above, each of the LC filter (consisting of Inductors L2 through L9 and capacitors C2 through C9) are used to filter and isolate the power supply line, going to each of the Receive Analog VDD pins and the Transmit Analog VDD pins. Each of these inductors should be of value 6.8uH, and each of these capacitors should be of value 2.2uF. The current consumption (via each of the Power Supply pins, of the XRT73L04 device) is presented below in Table 1. 4 TAN-046 Application Note - XRT73L04 4-Channel DS3/E3/STS-1 LIU IC Power Conditioning Requirements May 23, 2001 Revision 1.03 Table 1, The Current Consumption via each of the XRT73L04 Power Supply Pins Pin Number Description Measurements for Channel 0 33 Transmit Analog VDD - Channel 0 47 Transmit Analog VDD - Channel 0 58 Receive Digital VDD - Channel 0 78 Receive Analog VDD - Channel 0 Total Current Consumption - Channel 0 Amount of Current 49.5mA 4.22mA 16.1mA 48.6mA 118.42mA Measurements for Channel 1 24 Transmit Analog VDD - Channel 1 27 Transmit Analog VDD - Channel 1 51 Receive Digital VDD - Channel 1 86 Receive Analog VDD - Channel 1 Total Current Consumption - Channel 1 51.2mA 6.7mA 16.15mA 49.2mA 123.25mA Measurements for Channel 2 4 Transmit Analog VDD - Channel 2 134 Transmit Analog VDD - Channel 2 122 Receive Digital VDD - Channel 2 103 Receive Analog VDD - Channel 2 Total Current Consumption - Channel 2 42.7mA 4.5mA 16.28mA 48.3mA 111.78mA Measurements for Channel 3 13 Transmit Analog VDD - Channel 3 10 Transmit Analog VDD - Channel 3 128 Receive Digital VDD - Channel 3 95 Receive Analog VDD - Channel 3 Total Current Consumption - Channel 3 43.1mA 4.15mA 16.11mA 49.7mA 110.06mA 130 EXVDD Total Current Consumption - XRT73L04 Device 2.77mA 466.28mA For inductors L2 through L9, the user should select as large a value as the selected size (0805, 1210 or 1812 etc.) will allow while keeping the DC resistance of each inductor to less than 2 ohms. The goal is to keep the power supply voltage (at the VDD pins of the XRT73L04 device) above 3.135 volts. An example of an acceptable inductor would be the 1210-682J or the S1210-682K (each of size 1210) from API-Delevan. The 1210-682J inductor is spec'd to have a maximum dc resistance of 1.8ohms. Additionally, the 1210-682J inductor has a maximum current 5 TAN-046 Application Note - XRT73L04 4-Channel DS3/E3/STS-1 LIU IC Power Conditioning Requirements May 23, 2001 Revision 1.03 rating of 321mA. The S1210-682K inductor is spec'd to have a maximum dc resistance of 1.5ohms. Further, the S1210-682K has a maximum current rating of 372mA. 3.3 THE ZENER DIODE It is strongly recommended that a 3.6V 400mW Zener Diode be connected from the +3.3V supply to power GND to suppress power supply transients in case of excessive charge injection into the Ground plane. These transients can occur while connecting the remote terminal or test equipment to the board via coaxial cable. Such transients can expose integrated circuit devices to momentary `reverse' polarity or excessive (7V to 10V) power supply voltages. Most voltage regulators are too slow to respond to such transient conditions. NOTE: This zener diode is also useful for suppressing peak overshoots and ringing (in the power supply line) following a rapid ramp in the power supply voltage, due to events such as "hot-swapping", etc. An example of an acceptable 3.6V zener diode would be the 1N5914, which is available from various suppliers. 6 TAN-046 Application Note - XRT73L04 4-Channel DS3/E3/STS-1 LIU IC Power Conditioning Requirements May 23, 2001 Revision 1.03 3.4 DECOUPLING CAPACITORS We strongly recommend that the user provide de-coupling capacitors for each VDD pin of the XRT73L04 device (Analog as well as Digital). The placement and routing of these decoupling capacitors must be such to minimize the trace length (and in-turn, inductance) between the capacitor and the corresponding VDD pin, and the capacitor and the corresponding via (which connects to the GND plane). Miscellaneous Notes The component values shown for capacitors and inductors are to be used as guidelines only. Use following guidelines for selecting components: For decoupling capacitors use X7R for ceramic non-polar capacitors, solidtantalum for polar capacitors. Avoid Z5U and electrolytic capacitors. 7 TAN-046 Application Note - XRT73L04 4-Channel DS3/E3/STS-1 LIU IC Power Conditioning Requirements May 23, 2001 Revision 1.03 4.0 THE BNC CONNECTOR SHIELD As a general rule, we highly recommend that the customer either AC or DC couple the BNC connector shield to Frame or Chassis Ground. In the schematic design, we recommend that the customer AC couple the BNC connectors (on both the Transmit and Receive Sides) to Frame GND. Further, we also recommend that the customer also design in a Jumper, which permits installation personnel to DC couple the BNC connector shield to Frame GND, when set. Component selection for the for the Capacitor (used to AC couple the BNC Connector Shield to GND) The characteristics of a capacitor, to be used in this role are as follows. * This capacitor must be rated for high voltages. * This capacitor must impose minimum AC impedance to Frame GND. Therefore, the optimum choice for such a capacitor would be a capacitor that has a very high voltage rating and very large capacitance. The best capacitor that we could find that has both of these characteristics is a 1000pF capacitor that has a working voltage of 2000V. SOME ACCEPTABLE CAPACITORS for AC Coupling the BNC Connector to Frame GND Any of the following capacitors are suitable for this applicable. In all cases, these are Ceramic, X7R, 1000pF, 2kV, 10% capacitors which come in a 1812 case size. Manufacturer AVX AVX CALCHIP JARO JARO MURATA JOHANSON Part Number 1812GC102KA11A 1812GC102KAT2A CHV1812N2K0102KXT CC1812XR102JN202ER CC1812XR102KN202ER GRM43-2X7R102K2KVAL 202S43W102KV4E 8 5 4 3 DIGITAL VDD L1 1 L2 RECEIVE ANALOG VDD - CHANNEL 0 VDD 6.8uH (3.3V) 2 DVDD RxAVDD_0 15uH D1 C1 D 33uF C2 D1N5914 D 2.2uF (3.6V) 2.2uF C3 Install Close to the DC-to-DC Converter or Switching Regulator L3 TRANSMIT ANALOG VDD - CHANNEL 0 TxAVDD_0 6.8uH L4 RECEIVE ANALOG VDD - CHANNEL 1 RxAVDD_1 6.8uH C4 2.2uF 2.2uF C5 C C L5 TRANSMIT ANALOG VDD - CHANNEL 1 TxAVDD_1 6.8uH L6 RECEIVE ANALOG VDD - CHANNEL 2 RxAVDD_2 6.8uH C6 2.2uF 2.2uF C7 L7 TRANSMIT ANALOG VDD - CHANNEL 2 TxAVDD_2 6.8uH B B L8 RECEIVE ANALOG VDD - CHANNEL 3 RxAVDD_3 6.8uH C8 2.2uF 2.2uF C9 L9 TRANSMIT ANALOG VDD - CHANNEL 3 TxAVDD_3 6.8uH A A Title Power_Conditioning_Circuit Size B Date: 5 4 3 2 Document Number POWER_CON_SCH Wednesday, April 04, 2001 Rev 1.01 Sheet 1 1 of 1 5 4 3 2 DVDD 1 TxAVDD_0 C13 C14 0.1uF C10 0.1uF 0.1uF C11 0.1uF U1 R8 4.7k RxDATA_CH_0 130 58 DVDD RxDVDD0 74 75 52 ICT LOSTHR HOST/HW 61 RPOS0 LCV_OUT_CH_0 60 RNEG0/LCV0 RxCLK_CH_0 59 RCLK0 Rx_LOS_CH_0 RxLOL_CH_0 TxFAIL_CH_0 64 65 48 RLOS0 RLOL0 DMO0 TxAVDD0 TxAVDD0 RxAVDD0 RxAVDD_0 33 47 78 D C12 0.01uF RTIP0 J2 80 BNC 6 T2 1 4 C 1 2 D 3 T3001 79 R1 2 RRING0 R2 37.4 37.4 C38 1000pF (2kV) JP8 C 1 JUMPER LIU_RESET* LIU_CS* SERIAL_CLOCK_IN SERIAL_DATA_IN SERIAL_DATA_OUT 110 69 70 71 72 REF_CLOCK_0 66 TxCLK_CH_0 42 REG_RESET CS SCLK SDI SDO C15 R3 274 MTIP0 35 MRING0 36 TTIP0 34 0.01uF R4 274 EXCLK0 R5 TCLK0 TPDATA0 40 TNDATA0 R6 TRING0 131 111 16 77 76 82 46 44 TxOFF LOSMUTEN STS-1/DS3_Ch0 RLB0 LLB0 REQEN0 TAOS0 TxLEV0 62 129 RxDGND0 DGND 3 4 T3001 31.6 RxAGND0 AGND TxAGND0 TxAGND0 NOTE: BNC Connector Shield (on Transmit Side) is sometimes AC coupled to Frame Ground. 81 50 49 31 C35 1000pF (2kV) JP3 JUMPER A 100 Title XRT73L04_CHANNEL_0_DESIGN Size A Date: 5 4 B 32 XRT73L04_Channel_0 R7 A 1 2 41 T1 6 1 TxDATA_CH_0 1 2 31.6 B J1 BNC 3 Document Number TAN_046_CH_0 Wednesday, April 04, 2001 2 Rev 1.01 Sheet 1 of 1 1 5 4 3 2 1 DVDD TxAVDD_1 C17 C18 0.1uF C19 0.1uF 0.1uF RxAVDD_1 U2 51 RxDVDD1 RxDATA_CH_1 55 LCV_OUT_CH_0 54 RNEG1/LCV1 RxCLK_CH_1 53 RCLK1 RxLOS_CH_1 RxLOL_CH_1 TxFAIL_CH_1 67 68 26 RLOS1 RLOL1 DMO1 TxAVDD1 TxAVDD1 RxAVDD1 RTIP1 88 RPOS1 D C20 0.1uF J3 BNC 6 T4 1 4 C 1 2 D 24 27 86 3 T3001 87 R9 R10 37.4 C37 2 RRING1 37.4 1000pF (2kV) JP7 C 1 JUMPER REF_CLOCK_1 57 TxCLK_CH_1 30 EXCLK1 MTIP1 21 MRING1 20 TTIP1 25 R11 274 R12 274 C16 0.01uF R13 TCLK1 J4 BNC 1 TxDATA_CH_1 29 TPDATA1 28 TNDATA1 3 R14 TRING1 STS-1/DS3_Ch1 RLB1 LLB1 REQEN1 TAOS1 TxLEV1 56 RxDGND1 R15 100 A RxAGND1 AGND TxAGND1 TxAGND1 4 T3001 2 NOTE: BNC Connector JP4 Shield (on Transmit JUMPER Side) is sometimes AC coupled to Frame Ground. 89 63 19 22 C34 1000pF (2kV) XRT73L04_Channel_1 A Title XRT73L04_CHANNEL_1_DESIGN Size A Date: 5 4 B 23 31.6 83 85 84 90 45 43 1 1 B T3 6 2 31.6 3 Document Number TAN_046_CH_1 Wednesday, April 04, 2001 2 Rev 1.01 Sheet 1 of 1 1 5 4 3 2 1 DVDD TxAVDD_2 C21 C22 0.1uF C23 0.1uF 0.1uF RxAVDD_2 U3 D RxDVDD2 RxDATA_CH_2 119 LCV_OUT_CH_2 120 RNEG2/LCV2 RxCLK_CH_2 121 RCLK2 RxLOS_CH_2 RxLOL_CH_2 TxFAIL_CH_2 117 116 133 RLOS2 RLOL2 DMO2 TxAVDD2 TxAVDD2 RxAVDD2 4 134 103 RTIP2 101 RPOS2 D C24 0.1uF J5 BNC 6 T6 1 4 3 T3001 102 2 RRING2 R16 R17 37.4 C36 1000pF (2kV) JP6 37.4 JUMPER C 1 C 1 2 122 REF_CLOCK_2 115 TxCLK_CH_2 139 EXCLK2 MTIP2 2 MRING2 1 TTIP2 3 R18 274 R19 274 C25 0.01uF R20 TCLK2 140 TPDATA2 141 TNDATA2 T5 6 R21 TRING2 3 118 R22 A 4 T3001 RxDGND2 C33 1000pF (2kV) JP5 JUMPER RxAGND2 AGND TxAGND2 TxAGND2 NOTE: BNC Connector Shield (on Transmit Side) is sometimes AC coupled to Frame Ground. 100 109 6 132 1 E3_Ch2 STS-1/DS3_Ch2 RLB2 LLB2 REQEN2 TAOS2 TxLEV2 XRT73L04_Channel_2 100 A Title XRT73L04_CHANNEL_2_DESIGN Size A Date: 5 4 B 5 31.6 108 106 104 105 99 135 137 1 2 TxDATA_CH_2 1 2 31.6 B J6 BNC 3 Document Number TAN_046_CH_2 Wednesday, April 04, 2001 2 Rev 1.01 Sheet 1 of 1 1 5 4 3 2 1 DVDD TxAVDD_3 C27 C28 0.1uF C29 0.1uF 0.1uF RxAVDD_3 U5 D RxDVDD3 RxDATA_CH_3 125 LCV_OUT_CH_3 126 RNEG3/LCV3 RxCLK_CH_3 127 RCLK3 RxLOS_CH_3 RxLOL_CH_3 TxFAIL_CH_3 114 113 11 RLOS3 RLOL3 DMO2 TxAVDD3 TxAVDD3 RxAVDD3 10 13 95 RTIP3 93 RPOS3 D C30 0.1uF J7 BNC 6 T8 1 4 C 1 2 128 3 T3001 94 R23 2 RRING3 R24 37.4 37.4 C31 1000pF (2kV) JP1 C 1 JUMPER REF_CLOCK_3 123 TxCLK_CH_3 7 EXCLK3 MTIP3 16 MRING3 17 TTIP3 12 R25 274 R26 274 C26 0.01uF R27 TPDATA3 9 TNDATA3 R28 TRING3 107 98 96 97 91 136 138 124 R29 A E3_Ch3 STS-1/DS3_Ch3 RLB3 LLB3 REQEN3 TAOS3 TxLEV3 RxDGND3 T7 6 1 2 8 1 31.6 3 4 T3001 31.6 RxAGND3 AGND TxAGND3 TxAGND3 NOTE: BNC Connector Shield (on Transmit Side) is sometimes AC coupled to Frame Ground. 92 112 15 18 JP2 C32 1000pF (2kV) JUMPER XRT73L04_Channel_3 100 A Title XRT73L04_CHANNEL_3_DESIGN Size A Date: 5 4 B 14 2 TxDATA_CH_3 J8 BNC 1 B TCLK3 3 Document Number TAN_046_CH_3 Wednesday, April 04, 2001 2 Rev 1.01 Sheet 1 of 1 1 TAN-046 Application Note - XRT73L04 4-Channel DS3/E3/STS-1 LIU IC Power Conditioning Requirements May 23, 2001 Revision 1.03 APPENDIX A CONTACT INFORMATION FOR API-DELEVAN: Corporate Office API Delevan 270 Quaker Road East Aurora, NY 14052 Phone: 716-652-3600 FAX: 716-652-4814 email: apisales@delevan.com website: www.delevan.com 9 TAN-046 Application Note - XRT73L04 4-Channel DS3/E3/STS-1 LIU IC Power Conditioning Requirements May 23, 2001 Revision 1.03 APPENDIX B - REVISION CHANGE HISTORY CHANGES FROM REVISION 1.00 TO 1.01 1. Modified Schematic Design to include Jumpers JP5, JP6, JP7 and JP8. 2. Changed Capacitors C31, C32, C33, C34, C35, C36, C37 and C38 to 1000pF (2kV) capacitors. CHANGES FROM REVISION 1.01 TO 1.02 1. Included recommendations on handling the BNC Connector shield (Section 4.0) CHANGES FROM REVISION 1.02 TO 1.03 1. Included a list of acceptable part numbers for capacitors that can be used to AC couple the BNC Connector shield to Frame GND (Section 4.0). 10