1. Telefunken LVDS/M-LVDS as an alternative to RS-485/422

2. Why is LVDS attractive ? For short haul (<50m) LVDS offers a huge improvement in bandwidth LVDS provides significant power savings LVDS generates much less EMI LVDS is a standard I/O in FPGA and ASIC libraries simplifying translation Telefunken LVDS has extended common mode equaling the -7 to +12V of RS-485 2

3. Pervasive LVDS 3 100 350mV 3.5 mA LOGIC “1” 3.5 mA LOGIC “0” Close spacing of differential pair and opposite currents minimize EMI Noise coupled onto both lines cancels thus maintaining the differential voltage and boosting noise immunity LVDS is used extensively for reliable, low power, mid-range performance

4. “Common Mode” 400 mV GND 2.4V 1.4V 1.0V Common Mode Voltage Range where the Rx is guaranteed to operate TxRx 4 GND In noisy or distributed applications, there can be significant variation in local “GND” potential due to return resistance or ground bounce.

5. Common Mode Example 5 LVDS TxLVDS Rx Chasis Gnd “A” Chasis Gnd “B” Eg: Automotive Value of R changes over vehicle life R Several Volts of potential may develop between A & B

6. Extended Common Mode GND @ Tx GND @ Rx 2.4V Industry LVDS Spec Guarantees Operation Between Ground and 2.4V >1V of noise or Ground Potential Difference at Rx Causes Fault !!! 1V Telefunken LVDS extends the common mode to -7 to +12V, the same as RS-485

7. Extended Common Mode LVDS TI Extended Common Mode LVDS RS-485 Telefunken Extended Common Mode LVDS 2.4V 5V 12V 0 V - 4V - 7V 7

8. Robust Telefunken LVDS Telefunken LVDS is manufactured using our in-house proprietary Silicon- on-Insulator process. This provides: –Extended common mode -7 to +12V –Complete immunity to Latch-up –Minimal leakage and consistent operation up to ~150C –8KV ESD 8

9. Silicon on Insulator (SOI) Process Technology 9 SiO 2 Insulator SOI SOI eliminates parasitics and leakage paths for a very robust and quiet signal path. Latch-up immune and excellent high-temp performance (used for extended common mode LVDS) Conventional bulk substrate with parasitic PNs

10. TF048 Icc Leakage Tests 10 mA Degrees C No increase in leakage above 150C

11. TF048 VT threshold 11 mV Degrees C SPEC NOTE: VTH (max) is, Vcc = 3.6V (max) Common mode = 12V (max) NOTE: VTH (min) is, Vcc = 3.0V (min) Common mode = -7V (min) Worst case thresholds stay close to 0V above 150C

12. LVDS Features 12 LVDS EIA/TIA-644A Internal Termination Ext Common Mode -4 to +5 Ext Common Mode -7 to +12V Robust Latch-up Free SOI Fairchild X National X Maxim XX Texas Instruments XXX Telefunken XXXXX

13. Evaluation Kit Extended Common Mode 13 Eval Board includes 2 separate ground planes with LVDS connections configured via Cat 5e or ribbon cable

14. M-LVDS

15. M-LVDS Features 50 Smooth and balanced edges essential for driving backplanes (tr/tf ~2 ns) Must drive ~ 500mV Vod into distributed loads between 30 and 50ohms (glitchfree) Rx Common Mode spec is -1V to 3.4V 15

16. M-LVDS constant VOD M-LVDS maintains constant output VOD as load varies

17. M-LVDS Receiver Thresholds HIGH LOW TYPE 1TYPE 2 FAILSAFE

18. M-LVDS Type 2 Receiver – “Wired Or” Type 2 Receivers with offset can provide “Wired- Or” function for control signals. Floating bus has 0 V differential and M-LVDS type 2 Rx produces LOW output. Any driver can pull HI to interrupt

19. RS-485 and LVDS Specifications and Electricals

20. Driver Comparison

21. Receiver Comparison

22. Topologies Point to Point 22 Note : One Tx & Rx, terminated as close to the Rx as possible. Provides cleanest environment capable of the highest performance, datarate & jitter Suitable technologies – RS-485, RS-422, LVDS

23. RS-485 – Extended Common Mode LVDS Comparison 23 VOD (amplitude) VOS (offset) IOD (drive) Rise/Fall (typical) Datarate (typical) VID Common Mode EX CM LVDS 250-450 mV 1.125 to 1.375 V 2.5 to 4.5 mA.5 ns DC to 1000 Mbps.1 to 1 Volts -7 to +12 Volts RS-485 1.5 to 5 Volts -1 to 3 V 28 to 93 mA 5 to 50 ns DC to 10 Mbps.4 to 5 Volts - 7 to +12 Volts

24. Pt to pt Translation RS-485/422 to Extended CM LVDS 24 RS-485 TF048 22Ω 11Ω Resistor-divider network guarantees LVDS Vin amplitude of between 300mV and 1Volt Common mode of -7 to +12V meets RS-485 spec

25. Topologies Multi-drop, Multi-point 25 Multiple Rx (multi-drop) and/or multiple Tx (multipoint) Note : termination typically at each end of transmission line, eg 100Ω for 50Ω effective load. Suitable technologies – (capable of driving multiple distributed loads) – RS-485, M-LVDS

26. RS-485 – Multi-drop LVDS Comparison 26 VOD (amplitude) VOS (offset) IOD (drive) Rise/Fall (typical) Datarate (typical) VID Common Mode M-LVDS 480-650 mV.3 to 2.1 V 9 to 13 mA 1.5 ns DC to 250 Mbps.1 to 2.4 Volts -1 to 3.4 Volts RS-485 1.5 to 5 Volts -1 to 3 V 28 to 93 mA 5 to 50 ns DC to 10 Mbps.4 to 5 Volts - 7 to +12 Volts

27. Multidrop Translation RS-485 to M-LVDS 27 RS-485 Need to assess common mode, M-LVDS -1 to 3.4V TF176 43Ω 18 Ω TF176 43Ω 18 Ω

28. Summary Comparing RS-485 and LVDS/M-LVDS LVDS offers the following advantages: –Higher datarate (at distances up to 50m) –Significant Power savings –Significantly less EMI generation –Simplified interface with FPGAs & ASICs Telefunken LVDS matches the RS-485 common mode and is on latch-up free SOI Telefunken LVDS is an excellent alternative for short haul point-to-point links –Voltage divider termination needed if RS-485 driver used Telefunken M-LVDS is an alternative for multi-drop applications –Common mode and voltage divider termination/M-LVDS drive strength needs to be evaluated for mixed RS-485/M-LVDS network. 28