Rev. 1.00
204
September 11, 2018
Rev. 1.00
205
September 11, 2018
HT45F4050
A/D NFC Flash MCU
HT45F4050
A/D NFC Flash MCU
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
1.8
V and
4.0V. 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. When the device is in the
SLEEP
mode the Low Voltage Detector will disable even 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 LVDO transitions.
VDD
LVDEN
LVDO
V
LVD
t
LVDS
LVD Operation
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. In this case, the LVF 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 device
to wake-up from the IDLE 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 IDLE Mode.