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NCP304LSQ20T1
P1-P3
P4-P6
P7-P9
P10-P12
P13-P15
P16-P18
P19-P21
NCP304, NCP305
www
.onsemi.com
16
APPLICA
TION CIRCUIT INFORMA
TION
Figure 26. Microprocessor Reset Circuit
2
Input
1
Reset Output
GND
NCP304
LSQ27T1
Figure 27. Battery Charge Indicator
2
Input
1
Reset Output
GND
GND
V
DD
Reset
V
DD
NCP304
Series
4
4
Microprocessor
*
Required for
NCP305
V
in
< 2.7 ON
V
in
> 2.835 ON
T
o Additional Circuitry
*
2.85 V
2.70 V
Low state output if either
power supply is below the
respective undervoltage de-
tector threshold but greater
than 1.0 V
.
2
1
NCP305
LSQ45T1
Figure 28. Dual Power Supply Undervoltage Supervision
4
V
supply
2
1
NCP305
LSQ30T1
4
3.3 V
5.0 V
GND
Input
Reset Output
GND
Input
Reset Output
NCP304, NCP305
www
.onsemi.com
17
Figure 29. Microprocessor Reset Circuit with Additional Hysteresis
2
1
NCP301
LSN27T1
4
V
DD
GND
Reset Output
Input
R
H
R
L
NCP301
LSN27T1
NCP305
LSQ27T1
GND
Reset
V
DD
Microprocessor
Comparator hysteresis can be increased with the addition of
resistor R
H
. The hysteresis equations have been simplified and
do not account for the change of input current I
in
as V
in
crosses
the comparator threshold. The internal resistance, R
in
is simply
calculated using I
in
= 0.26
m
A at 2.6 V
.
V
in
Decreasing:
V
th
+
ǒ
R
H
R
in
)
1
Ǔ
ǒ
V
DET
*
Ǔ
V
in
Increasing:
V
th
+
ǒ
R
H
R
in
ø
R
L
)
1
Ǔ
ǒ
V
DET
*
)
V
HYS
Ǔ
V
HYS
= V
in
Increasing − V
in
Decreasing
T
est Data
V
th
Decreasing
(mV)
V
th
Increasing
(mV)
V
HYS
(mV)
R
H
(
W
)
R
L
(k
W
)
2.70
2.70
2.70
2.70
2.70
2.70
2.70
2.70
2.70
2.70
2.84
2.87
2.88
2.91
2.90
2.94
2.98
2.70
3.04
3.15
0.135
0.17
0.19
0.21
0.20
0.24
0.28
0.27
0.34
0.35
0
100
100
100
220
220
220
470
470
470
−
10
6.8
4.3
10
6.8
4.3
10
6.8
4.3
Figure 30. Simple Clock Oscillator
NCP301
LSN27T1
GND
Reset Output
Input
82 k
NCP301
LSN27T1
NCP302
HSQ27T1
C
5.0 V
100 k
C (
m
F)
f
OSC
(kHz)
I
Q
(
m
A)
0.01
2590
21.77
0.1
490
21.97
1.0
52
22.07
T
est Data
2
4
1
NCP304, NCP305
www
.onsemi.com
18
Figure 31. Microcontroller Systems Load Sensing
NCP301
LSN27T1
50 k
NCP301
LSN27T1
NCP305
LSQ09T1
V
supply
Load
R
sense
Input
2
4
GND
1
Reset Output
Microcontroller
GND
V
DD
If:
I
Load
t
V
DET
−
/R
sense
I
Load
w
(V
DET
−
+V
HYS
)/R
sense
Then:
Reset Output = 0 V
Reset Output = V
DD
This circuit monitors the current at the load. As
current flows through the load, a voltage drop with
respect to ground appears across R
sense
where
V
sense
= I
load
* R
sense.
The following conditions apply:
Figure 32. LED Bar Graph
NCP301
LSN27T1
2
NCP301
LSN27T1
NCP305
LSQ45T1
4
1
V
supply
NCP301
LSN27T1
2
NCP301
LSN27T1
NCP305
LSQ27T1
4
1
NCP301
LSN27T1
2
NCP301
LSN27T1
NCP305
LSQ18T1
4
1
Input
GND
Reset
Output
Input
GND
Reset
Output
Input
GND
Reset
Output
V
in
= 1.0 V to 10 V
A simple voltage monitor can be constructed by connecting several voltage detectors as shown above. Each LED will
sequentially turn on when the respective voltage detector threshold (V
DET−
+V
HYS
) is exceeded. Note that detector
thresholds (V
DET−
) that range from 0.9 V to 4.9 V in 100 mV steps can be manufactured.
P1-P3
P4-P6
P7-P9
P10-P12
P13-P15
P16-P18
P19-P21
NCP304LSQ20T1
Mfr. #:
Buy NCP304LSQ20T1
Manufacturer:
ON Semiconductor
Description:
Supervisory Circuits 2.0V Detector
Lifecycle:
New from this manufacturer.
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