MC34064, MC33064, NCV33064
www.onsemi.com
4
Figure 8. Clamp Diode Forward Current versus Voltage
Figure 9. Low Voltage Microprocessor Reset
Figure 10. Low Voltage Microprocessor Reset with Additional Hysteresis
80
60
40
20
0
0 0.4 0.8 1.2 1.6
V
F
, FORWARD VOLTAGE (V)
, FORWARD CURRENT (mA)
F
I
V
in
= 0 V
T
A
= 25°C
A time delayed reset can be accomplished with the
addition of C
DLY
. For systems with extremely fast
power supply rise times (<500 ns) it is recommended
that the RC
DLY
time constant be greater than 5.0 ms.
V
th(MPU)
is the microprocessor reset input threshold.
t
DLY
= RC
DLY
In
1
1 -
V
th(MPU)
Power
Supply
+
-
Input
R
Reset
C
DLY
Microprocessor
Circuit
1.2 V
ref
GND
-
+
Power
Supply
+
-
Input
R
L
Reset
Microprocessor
Circuit
1.2V
ref
GND
-
+
V
H
≈
4.6 R
H
+ 0.02
DV
th(lower)
≈ 340 R
H
x 10
-6
Where:R
H
≤ 150 W
Where:R
L
≥ 1.5 W, ≤ 10 kW
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
CC
crosses the comparator threshold
(Figure 4). An increase of the lower threshold DV
th(lower)
will be observed due to I
in
which is typically 340 mA at
4.59V. The equations are accurate to ±10% with R
H
less than 150 W and R
L
between 1.5 kW and 10 kW.
I
in
R
H
V
in
R
L
TEST DATA
V
H
(mV)
DV
th
(mV)
R
H
(W)
R
L
(kW)
20
51
40
81
71
112
100
164
190
327
276
480
0
3.4
6.8
6.8
10
10
16
16
34
34
51
51
0
10
20
20
30
30
47
47
100
100
150
150
0
1.5
4.7
1.5
2.7
1.5
2.7
1.5
2.7
1.5
2.7
1.5
