MC34164, MC33164, NCV33164
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6
Figure 15. Low Voltage Microprocessor Reset With Additional Hysteresis
(MC3X164−5 Shown)
Power
Supply
1.2 V
ref
Microprocessor
Circuit
R
L
GND
Reset
Comparator hysteresis can be increased with the addition of resistor R
H
. The hysteresis equation has been simplified and does not account for the change of input current
I
in
as V
in
crosses the comparator threshold (Figure 8). An increase of the lower threshold V
th(lower)
will be observed due to I
in
which is typically 10 A at 4.3 V. The
equations are accurate to ±10% with R
H
less than 1.0 k and R
L
between 4.3 k and 43 k.
V
H
≈
4.3 R
H
R
H
MC3X164-5
I
in
V
in
Test Data
V
H
(mV)
V
th
(mV)
R
H
()
R
L
(k)
60
103
123
160
155
199
280
262
306
357
421
530
0
1.0
1.0
1.0
2.2
2.2
2.2
4.7
4.7
4.7
4.7
4.7
0
100
100
100
220
220
220
470
470
470
470
470
43
10
6.8
4.3
10
6.8
4.3
10
8.2
6.8
5.6
4.3
R
L
+ 0.06
V
th(lower)
≈ 10 R
H
x 10
-6
where: R
H
≤ 1.0 k
43 k ≥ R
L
≥ 4.3 k
Figure 16. Voltage Monitor Figure 17. Solar Powered Battery Charger
Figure 18. MOSFET Low Voltage Gate Drive Protection Using the MC3X164−5
1.2 V
ref
Input
270
Reset
GND
Power
Supply
1.2 V
ref
Input
1.0 k
GND
1.2 V
ref
Input
GND
Solar
Cells
R
L
MTP3055EL
MC3X164-5
V
CC
4.3V
Overheating of the logic level power MOSFET due to insufficient
gate voltage can be prevented with the above circuit. When the
input signal is below the 4.3 V threshold of the MC3X164-5, its
output grounds the gate of the L
2
MOSFET.
Reset
Reset
