Rev: 1.1 Application Note MLX75605CA Revision 1.0 1.1 Date 15/10/2008 26/10/2008 Author ADE CVA Change Creation Addition of footprint dimensions Introduction This document describes the connections between MLX75605 MOST150 Fiber Optics Transceivers and MOST control part. It explains how to connect the different pins, their role, necessary external components, and some layout recommendations. Pin List and Descriptions DATAOUT+ DATAOUTRX VCC_RX1 GND_RX1 RESERVED2 VDD_RX2 GND_RX2 STATUS GP3_RX SHIELD SHIELD SHIELD SHIELD TX RESERVED1 GP2_TX VCC_TX1 VCC_TX2 GND_TX1 GND_TX2 DATAIN+ DATAI- Author: ADE GP4_RX GP1_TX /RST 1 MELEXIS CONFIDENTIAL AND PROPRIETARY 26/10/2008 Rev: 1.1 Pin Number Pin name Description 1 DataOUT Plus LVDS Positive Output. Routing To LVDS Plus input of MOST should be mirrored together controller with minus input. 2 DataOUT Minus LVDS Negative Output Routing To LVDS minus input of MOST should be mirrored together controller with plus input. 3 VCC_Rx1 Supply voltage for Receiver Connected to Rx VDD 4 GND_Rx1 Ground for Receiver Connected to Rx GND 5 STATUS Indicates if modulated light is received within operation frequency range. If the received light power level and frequency is greater than threshold, then voltage on the status pin is «LOW». With the status pin the power supply of the whole MOST devices can be switched ON. Connected to Status input of controller 6 Shield Shield pin connected to die pad of package Connected to Sh_GND 7 Shield Shield pin connected to die pad of package Connected to Sh_GND 8 Reserved1 Connect to GND through 0ohm resistor. Used for factory test purpose. M3dB function Connected to possible M3dB function of controller (Not available on MLX75605CA revision) 9 VCC_Tx1 Supply voltage for Transmitter Connected to Tx VDD 10 GND_Tx1 Ground for Transmitter Connected to Tx GND 11 DataIN Plus LVDS Negative Input From LVDS minus output of MOST controller 12 DataIN Minus LVDS Positive Input From LVDS plus output of MOST controller 13 /RST Optical Output power disabling. Connected to /RST of MOST Active-low logic signal disables controller the optical output 14 Tx_GP1 Currently used for Test output pin. Should be left unconnected Should be floating 15 GND_Tx2 Ground for Transmitter Connected to Tx GND 16 VCC_TX2 Supply voltage for Transmitter Connected to Tx VDD Author: ADE Connection 2 MELEXIS CONFIDENTIAL AND PROPRIETARY 26/10/2008 Rev: 1.1 17 Tx_GP2 Factory Test input. Should left unconnected. Should be floating 18 Shield Shield pin connected to die pad of package Connected to Sh_GND 19 Shield Shield pin connected to die pad of package Connected to Sh_GND 20 GP3_RX Factory test output. Automatic Gain Control analog output Should be left unconnected Should be floating. (Connected to 10nF for MLX75603CA only) 21 GND_Rx2 Ground for Receiver Connected to Rx GND 22 VCC_Rx2 Supply voltage for Receiver Connected to Rx VDD 23 Reserved2 Connect to VCC_RX2 through 0-ohm resistor. Used for factory test purpose. Connected to Rx VDD. 24 GP4_RX Should left unconnected. Should be floating Author: ADE 3 MELEXIS CONFIDENTIAL AND PROPRIETARY 26/10/2008 Rev: 1.1 Schematics VDD _Tx VDD_ Rx 10uF 100 10uF DATAOUT+ DATAOUT- LVDS Outputs M3dB MOST CONTROLLER Including supply control LVDS Outputs VDD_RX2 STATUS GP3_RX GND_RX2 SHIELD SHIELD SHIELD SHIELD 10nF TX RESERVED1 GP2_TX VCC_TX1 VCC_TX2 100nF GND_TX1 DATAIN+ DATAI- Author: ADE RESERVED2 RX 100nF VCC_RX1 GND_RX1 100 /RST GP4_RX 4 26/10/2008 MELEXIS CONFIDENTIAL AND PROPRIETARY GND_TX2 GP1_TX /RST Rev: 1.1 External Components - To guarantee correct impedance matching between controller and transceiver, it is necessary to add 100ohms between both LVDS I/Os. To maximize their efficiency, the resistors have to be placed close to the LVDS receiver buffer. This means that, for data coming from transceiver, resistor has to be placed close to the MOST controller and for data arriving at transceiver, resistor should be placed close to this one. - As Transmitter can be disabled by supply shut down, Receiver and transmitter supplies have to be fully decoupled. - 10uF has can be used for global decoupling. - Then, 100nF bypass capacitors can be connected for each device: one for Receiver chipset and one for transmitter. It is recommended that, these capacitors are with low equivalent serial resistance, in order to increase decoupling efficiency with high current. These capacitors have to be placed close to the device to minimize routing impact. - For MLX75605CA only, a 10nF decoupling capacitor should be added on pin #20. This capacitor should be considered as a containment action for a small design weakness in Automatic Gain control on the receiver chip. Layout Recommendations - - It is important to decouple supply lines to the maximum. This means that, supply lines have to be routed in a star configuration. For VDD side, it is recommended to short both VCC from each device, respectively transmitter and receiver, together routing under the device. Pinout of supply and ground lines have been made such a way that, they face each other. This allows direct connection with the shortest route. For GND side, it is advised to fully decouple ground from transmitter and ground from receiver to guarantee no cross talk. A ground plate has been placed all around FOT and especially around LVDS High speed tracks to fully isolate them. Moreover, device allows shield to be grounded to Ground plate. This allows optimizing EMc performance. Author: ADE 5 MELEXIS CONFIDENTIAL AND PROPRIETARY 26/10/2008 Rev: 1.1 Footprint – recommendation All dimensions given in mm. 11x means that this dimension is repeated 11 times in this footprint drawing (only the bottom half of the drawing) Due to the symmetry axis this is also valid for the upper half of the drawing 24x means that this dimension is repeated 24 times in this footprint drawing (for the bottom half as well as for the upper half of the drawing) Author: ADE 6 MELEXIS CONFIDENTIAL AND PROPRIETARY 26/10/2008