SMBus 2 in Systems with I2C(tm) - SBS-IF Smart Battery System ...

SBS-IF Portable Design ConferenceSMBus 2.0 in Systems with I 2 C*Dale StolitzkaDirector, Architecture LabAnalog Devices, Inc.January 2002Other names and brands may be claimed as the property of others.*All trademarks cited in this presentation are acknowledged as the property of their respective owners.

SBS-IF Portable Design ConferenceMixing SMBus and I 2 C devices,can I get in trouble?• SMBus layers usedthroughout system• Designers mix-in I 2 Cdue to availability• DC electrical levelincompatibilities andAC timeout issueswill arise!SMBus ≠ I 2 CEEPROMTemp/fanSMBusHost controllerDIMMPCI ABatteryPCI BChargerAnalog Devices, Inc. – Smart Battery Data Expo

SBS-IF Portable Design ConferenceDC parameters matterV DD= 3.3V ± 10%2.54V0.89VV OL@ 4mA (SMBus high power) 0.4 VI LEAK(SMBus high power) 10 µAAnalog Devices, Inc. – Smart Battery Data Expo

SBS-IF Portable Design ConferenceAC timing and timeouts matterI 2 CSMBusTHD; DAT 0 ns 300 nSRISE TIME 1000 ns from 0.89V to 2.54V 1000 ns from 0.65V to 2.25VFALL TIME* output stage:250 ns from 2.54V to 0.89V300 ns from 2.25V to 0.65V• AC timing differences affect component selection• SMBus uses bus timeouts; I 2 C has no timeouts and nominimum data rateAnalog Devices, Inc. – Smart Battery Data Expo

SBS-IF Portable Design ConferenceWhat if the bus is stuck?• Host detects timeout• Watch for slave timeout• Send Stop condition• Is the bus clear or at idle?• if SMBDAT (SDA) is low, theanswer is no• A robust host will clock the busuntil SMBDAT returns to high2SMBusHostSlaveM/B sensoror EEPROMAnalog Devices, Inc. – Smart Battery Data Expo

SBS-IF Portable Design ConferenceDesigning for interoperability• Host controllers could support dual protocol operation• Sink I OL> 4mA• Output I 2 C ‘1’ and SMBus ‘0’ levels.• Accept SMBus ‘1’ and I 2 C ‘0’ levels.• Output data with SMBus hold time• Accept data with I 2 C hold time• Watch for mid-byte start and stop conditions• Host monitors and proxies for device timeouts & clears the bus• Using the packet error checking will help robustness• Mixing I 2 C and SMBus masters can be problematic• I 2 C Master-write timing can potentially cause problems witharbitrationAnalog Devices, Inc. – Smart Battery Data Expo

Power IC’s for portablesADP330X, ADP3610/11LCD Driver PSADP3025ADP3022Main/SystemDC/DCADP3422/3415ADP3203/ADP3204/3415CPU Core PowerADP3605HDD+12+ 53.32.51.81.51.251.20.8Intel MobileProcessorsMemoryDDRHUB/PCCARDAGPRTCVIDADP33XXLDOADP3801/02/10/11Battery ChargerADP3806Battery Battery

New ADP3806 battery charger• Accurate to meet SBC spec• ±0.4% at 25°C• ±0.75% from 0°C to 85°C• Fast• 500KHz switcher• small inductors• Flexible• fixed output for 3 or 4 Li + cells• variable output versions• Safe• Rail-to-rail current sensingSMBusHost1chargerADP38062SMBuspowersourcebattery