1、Temperature VariationThe Unappreciated Environmental Factor in the Stability of Multigigabit Automotive EthernetAlireza Razavi,Ragnar Jonsson|MarvellIEEE SA Ethernet&IP Automotive Technology Day19-20 September 2023,So Paulo,Brazil 2023 Marvell.All rights reserved.2Vehicles operate in the extremes 20

2、23 Marvell confidential.All rights reserved.2 2023 Marvell.All rights reserved.3Two types of temperature tests“Error-free”links at any valid temperature“Error-free”as temperature ramps across rangeStatic testsRamp tests 2023 Marvell.All rights reserved.4Static testing process is well-definedPHY link

3、s without error at any valid temperatureThe underlying standard provides a limit on cable/board electrical characteristics For all temperatures,the cable/board should not violate these requirements on insertion loss,return loss,jitter,etc.Ramp testing is well-defined,too,but to get good resultshard

4、2023 Marvell.All rights reserved.5Whats so hard about passing a ramp test?2023 Marvell confidential.All rights reserved.5 2023 Marvell.All rights reserved.6First things first:measurement setup 15m shielded twisted pair with four inline connectors Temperature range:-40 to 105 Celsius15m cableDUTLKP 2

5、023 Marvell.All rights reserved.7Channel insertion loss increases with temperature Source:Marvell15m BASE-T1 cable 2023 Marvell.All rights reserved.8How do we address insertion loss variability?CoderEqualizer/coderAnalog to digital convertorDigital to analog convertorEcho cancelerTransmitbitsReceive

6、dbitsHybridLink partnerCableProblem:variability in cable insertion loss over temperatureOverdesign analog front-endand apply active gain controlApply fasteradaptive equalizationAddressing insertion loss variability increases chip size,power and cost 2023 Marvell.All rights reserved.9Cable delay vari

7、es with temperatureDelay variation 1.7 symbol duration of 10GBASE-T1Source:Marvell0.3ns 2023 Marvell.All rights reserved.10How do we address channel delay variability?Addressing delay variability increases chip size,power and costCoderEqualizer/coderAnalog to digital convertorDigital to analog conve

8、rtorEcho cancelerTransmitbitsReceivedbitsHybridLink partnerCableProblem:variability in channel delay over temperatureApply active sampling-time adjustments Apply fasteradaptive equalization 2023 Marvell.All rights reserved.11Return loss over temperature is unpredictable Source:Marvell 2023 Marvell.A

9、ll rights reserved.12How do we address channel return loss variability?CoderEqualizer/coderAnalog to digital convertorDigital to analog convertorEcho cancelerTransmitbitsReceivedbitsHybridLink partnerCableProblem:variability in channel return loss over temperatureApply active sampling-time adjustmen

10、ts Apply faster adaptive echo cancelationAddressing insertion loss variability increases chip size,power and cost 2023 Marvell.All rights reserved.13Summary:passing the temperature ramp test Design with margin:higher power and price1Design with temp-awareness:complex design and test2OR 2023 Marvell.

11、All rights reserved.14So,we can fix it,right?2023 Marvell confidential.All rights reserved.14 2023 Marvell.All rights reserved.15Not so fast 2023 Marvell confidential.All rights reserved.15 2023 Marvell.All rights reserved.16Insertion loss over temp varies by cable brand Source:Marvell 2023 Marvell.

12、All rights reserved.17Call to actionTo create more economical,reliable Ethernet SolutionsWe need to define reasonable min and max boundaries for cable performance over temperature 2023 Marvell.All rights reserved.18Common mode to differential gain varies over tempSource:Marvell10dBVarying temp affec

13、ts the behavior of device in ElectroMagnetic Interference test 2023 Marvell.All rights reserved.19Key takeaways1234Insertion loss and related metrics exhibit high variability over temperatureDegree of temperature-induced variability differs between cable brandsPenalties are steep for overdesigning PHYs to accommodate max variabilityMin/max limits should be established for performance variability over tempThank You 2023 Marvell.All rights reserved.22Special thanksEduardo Munoz-Gutierrez Mattias Nilsson Danny Chan Mark Davis