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Rev. 1.40
134
March 29, 2019
Rev. 1.40
135
March 29, 2019
HT45F23A/HT45F24A
TinyPower
TM
Flash MCU with OPA & Comparators
HT45F23A/HT45F24A
TinyPower
TM
Flash MCU with OPA & Comparators
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
LVD2~LVD0
: 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
LVD Operation
The Low Voltage Detector function operates by comparing the power supply voltage, V
DD
, with a
pre-specified voltage level stored in the LVDC register. This has a range of between 2.0V and 4.4V.
When the power supply voltage, V
DD
, falls below this pre-determined value, the LVDO bit will be
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 devices are 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
LVDS
should be allowed for the circuitry to stabilise before reading the
LVDO bit. Note also that as the V
DD
voltage may rise and fall rather slowly, at the voltage nears that
of V
LVD
, there may be multiple bit L
VDO
transitions.
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
LVD
after the LVDO bit has been
set high by a low voltage condition. When the devices are powered down the Low Voltage Detector
will remain active if the LVDEN bit is high. In this case, the LVDF interrupt request flag will be
set, causing an interrupt to be generated if V
DD
falls below the preset LVD voltage. This will cause
the devices to wake-up from the SLEEP or IDLE Mode, however if the Low Voltage Detector wake
up function is not required then the LVDF flag should be first set high before the devices enters the
SLEEP or IDLE Mode.
LVD Operation