Voltage detectors bd48xxg/fve bd49xxg/fve – Rainbow Electronics BD4923G_FVE User Manual
Page 8
Hysteresis > R X { (Circuit current at ON) - (Circuit current at OFF) }
3)Application circuit when it is used as Power-on reset is shown below.
(However, it can be used for only BD48XXG/FVE series.)
If the power supply voltage is lower than the guaranteed range, power-on reset of the microcontroller is necessary
to prevent program runaways and unwanted memory register updates. A power-on reset circuit used with
BD48XXG/FVE series (Nch open drain) is shown in Fig.20. C and R conneceted to V
DD
pin of RESET IC make
the wave rounding of the V
DD
pin and generate input signal with time constant. When the input power supply is
fallen, the electric charge of the capacitor is discharged through Di connected between V
DD
pin and V
DD
.
The value of the resister R should be enough to prevent malfunction caused by circuit current through
BD48XXG/FVE series. Set in such a way that the following expression stands:
Do not use BD49XXG/FVE series (CMOS output) for the power-on reset because malfunction may occur.
(Oscillation at output etc.) The feed through current (CMOS output) at detection may cause malfunction
mentioned above. (Feed through current is the current flowed from V
DD
into GND instantly when output
goes "H" "L". )
BD48XXX
Micro
controller
V
DD
R
C
R
L
Di
GND
2)Application circuit when microcontroller is reset with OR connection of the two types of the detection voltage
is shown below.
When there is more than one system power supply and it is necessary to individually monitor the power supply
(V
DD1
, V
DD2
) to reset the microcontroller, open drain output type BD48XXG/FVE series can be connected to
form an OR circuit as shown in Fig.19 for pulling up to an arbitrary voltage (V
DD3
) to adjust the H voltage of the
output to the microcontroller power supply (V
DD3
).
Fig.19
Fig.20
Fig.21
CMOS output circuit
Fig.22
Current consumption Vs. power supply voltage
BD48XXX
V
DD2
V
DD1
BD48XXX
V
DD3
R
L
GND
Micro
controller
R
ST
V
OUT
V
DD
GND
Feed through current
Feed through current
0
V
DD
V
S
I
CC
8/15
Voltage detectors
BD48XXG/FVE
BD49XXG/FVE
Rev.A