Holtek BS82B12A-3 - Low Voltage Detector - LVD; LVD Registe

Rev. 1.20 146 January 23, 2015 Rev. 1.20 147 January 23, 2015
BS82B12A-3/BS82C16A-3/BS82D20A-3
Touch Key 8-Bit Flash MCU with LED/LCD Driver
BS82B12A-3/BS82C16A-3/BS82D20A-3
Touch Key 8-Bit Flash MCU with LED/LCD Driver
Low Voltage Detector – LVD
EachdevicehasaLowVoltageDetectorfunction,alsoknownasLVD.Thisenablesthedeviceto
monitorthepowersupplyvoltage,V
DD
,andprovidesawarningsignalshoulditfallbelowacertain
level.Thisfunctionmaybeespeciallyusefulinbatteryapplicationswherethesupplyvoltagewill
graduallyreduceasthebatteryages,asitallowsanearlywarningbatterylowsignaltobegenerated.
TheLowVoltageDetectoralsohasthecapabilityofgeneratinganinterruptsignal.
LVD Register
TheLowVoltageDetectorfunctioniscontrolledusingasingleregisterwiththenameLVDC.Three
bitsinthisregister,VLVD2~VLVD0,areusedtoselectoneofvexedvoltagesbelowwhicha
lowvoltageconditionwillbedetemined.AlowvoltageconditionisindicatedwhentheLVDObitis
set.IftheLVDObitislow,thisindicatesthattheV
DD
voltageisabovethepresetlowvoltagevalue.
TheLVDENbitisusedtocontroltheoverallon/offfunctionofthelowvoltagedetector.Settingthe
bithighwillenablethelowvoltagedetector.Clearingthebittozerowillswitchofftheinternallow
voltagedetectorcircuits.Asthelowvoltagedetectorwillconsumeacertainamountofpower,itmay
bedesirabletoswitchoffthecircuitwhennotinuse,animportantconsiderationinpowersensitive
batterypoweredapplications.
LVDC Register
Bit 7 6 5 4 3 2 1 0
Name — — LVDO LVDEN — VLVD2 VLVD1 VLVD0
R/W — — R R/W — R/W R/W R/W
POR — — 0 0 — 0 0 0
Bit7~6 Unimplemented,readas"0"
Bit5 LVDO:LVDOutputFlag
0:NoLowVoltageDetect
1:LowVoltageDetect
Bit4 LVDEN:LowVoltageDetectorControl
0:Disable
1:Enable
Bit3 Unimplemented,readas"0"
Bit2~0 VLVD2 ~ VLVD0:SelectLVDVoltage
000:2.0V
001:2.2V
010:2.4V
011:2.7V
100:3.0V
101:3.3V
110:3.6V
111:4.0V
Note:TheV
LVR
ofthesethreedevicesisxedat2.55V,sotheV
LVD
shouldbesetto
2.7V~4.0V.