Rev. 1.20
146
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Rev. 1.20
147
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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 five fixed 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 fixed at 2.55V, so the V
LVD
should be set to
2.7V~4.0V.