ADC 6021 Dokumentacja Pobierz pdf (Strona 84)

MYXPM6021*

Revision 1.1 - 10/21/14

*Advanced information. Subject to change without notice.

MYXPM6021*

Form #: CSI-D-685 Document 011

14.3 Backup Battery Management

CongurationandstatusregistersofMYXPM6021,andtimekeepinglogic(poweredbyaplatformvoltagerailVRTC)in

theSOCarebacked-upbyasupercapacitororcoincellbatteryincaseofSOCpowerloss(e.g.,mainbatterychanged).

TheVRTCissuppliedusuallythroughadiodebyeitherV3P3AorVBATBKUPwithV3P3Atakingprioritywheneveritis

available.Ifa SOCpowerloss isofan extendedduration,the back-upsupplywill fallbelowtheminimumoperational

voltage,VMIN,andthecontentoftheregisterswillbelostandresettodefaultvalue.

14.3.1 Backup Battery Charger

TheBackupBatteryChargerisusedtochargecoincellLi-Ionbatteriesor“Super-capacitors”.Duetothechemistryand/

orrelativelyhighinternalresistanceofthesebatteriesitisnecessarytochargeintwostages:aconstantcurrentstage;

andaconstantvoltagestage.Inessencethismeansthatthechargeractsasacurrentlimitedvoltagesource.Thetarget

voltageandmaximumchargecurrentarecongurableviaseparate2-bitregistersettings.

Inadditiontobatterychargingthecircuitmustprotectagainstdischargingofthebackupbatteryincaseswhenthesystem

supplydropsbelowthebackupbatteryvoltage.Forthisreasonanalways-onprotectioncircuitisutilizedwhichshutsoff

thereversecurrentpathasrequired.

To facilitate low power system modes wherein no oscillator is running, the Backup Battery Charger is capable of

autonomouslyself-regulatingitsstatesuchastostopchargingwhenthebatteryisfullandtostartonceagainwhenthe

batteryissufcientlyemptied.

14.3.2 Power Consumption

TheMYXPM6021logicsuppliedbytheVRTCdomainwillconsume<5μA.

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ADC 6021 Dokumentacja Strona 84