Holtek HT66F20 - Low Voltage Detector - LVD; LVD Register

Rev. 2.50 226 June 22, 2017 Rev. 2.50 227 June 22, 2017
HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
A/D Flash MCU with EEPROM
HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
A/D Flash MCU with EEPROM
Low Voltage Detector – LVD
EachdevicehasaLowVoltageDetectorfunction,alsoknownasLVD.Thisenabledthedeviceto
monitorthepowersupplyvoltage,V
DD
,andprovide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eight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Detected
1:LowVoltageDetected
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:4.4V