Lvd Ope�Ation - Holtek HT66F488 Manual

LVD Operation
The Low Voltage Detector function operates by comparing the power supply voltage, V
pre-specified voltage level stored in the LVDC register. This has a range of between 2.0V and 4.0V.
When the power supply voltage, V
set high indicating a low power supply voltage condition. The Low Voltage Detector function is
supplied by a reference voltage which will be automatically enabled. When the device is powered
down the low voltage detector will remain active if the LVDEN bit is high. After enabling the Low
Voltage Detector, a time delay t
LVDO bit. Note also that as the V
of V , there may be multiple bit LVDO transitions.
LVD
The Low Voltage Detector also has its own interrupt which is contained within one of the Multi-
function interrupts, providing an alternative means of low voltage detection, in addition to polling
the LVDO bit. The interrupt will only be generated after a delay of t
set high by a low voltage condition. When the device is powered down the Low Voltage Detector
will remain active if the LVDEN bit is high. In this case, the LVF interrupt request flag will be set,
causing an interrupt to be generated if V
device to wake-up from the SLEEP Mode, however if the Low Voltage Detector wake up function is
not required then the LVF flag should be first set high before the device enters the SLEEP Mode.
When LVD function is enabled, it is recommenced to clear LVD flag first, and then enables interrupt
function to avoid mistake action.
Rev. 1.21
, falls below this pre-determined value, the LVDO bit will be
DD
should be allowed for the circuitry to stabilise before reading the
LVDS
voltage may rise and fall rather slowly, at the voltage nears that
DD
V D D
V
L V D
L V D E N
L V D O
t
L V D S
LVD Operation
falls below the preset LVD voltage. This will cause the
DD
168
HT66F488/HT66F489
A/D Flash MCU with EEPROM
after the LVDO bit has been
LVD
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, with a
DD