MC3425 Datasheet, PDF (5/12 Pages) ON Semiconductor – POWER SUPPLY SUPERVISORY/ OVER AND UNDERVOLTAGE PROTECTION CIRCUIT

MC3425
APPLICATIONS INFORMATION
Figure 11. Overvoltage Protection and
Undervoltage Fault Indication with
Programmable Delay
+VO
Vin
R1A
+
Power
Supply
4.5V to 40V
–
R2A
R1B
8
VCC
U.V. Fault
4 U.V.
U.V. 6 ^Indicator
Sense
IND
IH
MC3425
3 O.V.
Sense
O.V. ¹
DRV
O.V.
U.V.
DLY Gnd DLY
R2B ^{2 7 5}
CDLY
CDLY
Gnd
U.V. Hysteresis = IH
tDLY = 12500 CDLY
R1B R2B
R1B + R2B ^{, VO(trip) – 2.5 V}
R1A
1 + _R2A
AC Line
Figure 12. Overvoltage Protection of 5.0 V
Supply with Line Loss Detector
+5.0V
Power
Supply
15k
VO = 5.0 V
VO(trip) = 6.25 V
8
VCC
1.0k
4 _U.V.
Sense
U.V. ⁶
IND
MC3425
3 _O.V.
Sense
O.V. ¹
DRV
Line Loss
Output
10k
O.V.
U.V.
DLY Gnd DLY
100
27 5
0.01µF
0.33µF
U.V. Sense
Pin 4
2.5V
U.V. DLY
2.5V
Pin 5
U.V. IND
OFF
Pin 6
ON
Figure 13. Overvoltage Audio Alarm Circuit
+
12V
Power
Supply
+VO
8
12k
VCC
Alarm On when:
VO = 13.6 V
3 ^O.V.
Sense
O.V. ₁
DRV
2.7k
MC3425
4 _U.V.
Sense
82k _{U.V. O.V.}
DLY DLY Gnd
6.8k ^{5 2 7}
100Ω
0.1µF
Gnd
Figure 14. Programmable Frequency Switch
Input Signal 5.0µF
I.V. p–p
10k
10k
12V
8
VCC
3 _O.V.
Sense
O.V. 1
DRV
Output Pulse when:
f(input) <
1
25000 CDLY
MC3425
1.0k
4 U.V.
Sense
U.V.
O.V.
DLY Gnd DLY
57 2
0.1µF
CDLY
O.V. Sense
Pin 3
2.5V
O.V. DLY
Pin 2
2.5V
ON
O.V. DRV
Pin 1
OFF
MOTOROLA ANALOG IC DEVICE DATA
5