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PDF MC3423 Data sheet ( Hoja de datos )
| Número de pieza | MC3423 | |
| Descripción | Overvoltage Crowbar Sensing Circuit | |
| Fabricantes | ON Semiconductor | |
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MC3423
Overvoltage Crowbar
Sensing Circuit
This overvoltage protection circuit (OVP) protects sensitive
electronic circuitry from overvoltage transients or regulator failures
when used in conjunction with an external “crowbar” SCR. The
device senses the overvoltage condition and quickly “crowbars” or
short circuits the supply, forcing the supply into current limiting or
opening the fuse or circuit breaker.
The protection voltage threshold is adjustable and the MC3423 can
be programmed for minimum duration of overvoltage condition
before tripping, thus supplying noise immunity.
The MC3423 is essentially a “two terminal” system, therefore it
can be used with either positive or negative supplies.
Features
• Pb−Free Package is Available
MAXIMUM RATINGS
Rating
Symbol
Value
Unit
Differential Power Supply Voltage
VCC−VEE
40
Vdc
Sense Voltage (1)
VSense1
6.5www.DataShVeedt4cU.com
Sense Voltage (2)
VSense2 6.5 Vdc
Remote Activation Input Voltage
Vact 7.0 Vdc
Output Current
IO 300 mA
Operating Ambient Temperature Range
TA
0 to +70
°C
Operating Junction Temperature
TJ 125 °C
Storage Temperature Range
Tstg −65 to +150 °C
Maximum ratings are those values beyond which device damage can occur.
Maximum ratings applied to the device are individual stress limit values (not
normal operating conditions) and are not valid simultaneously. If these limits
are exceeded, device functional operation is not implied, damage may occur
and reliability may be affected.
Vin
Current
Limited
DC
Power
Supply
+
Cout
O. V. P.
MC3423
Vout
Figure 1. Simplified Application
http://onsemi.com
8
1
MARKING
DIAGRAMS
PDIP−8
P1 SUFFIX
PLASTIC PACKAGE
CASE 626
MC3423P1
AWL
YYWW
MC3423P1
A
WL
YY
WW
= Device Code
= Assembly Location
= Wafer Lot
= Year
= Work Week
8
8 SOIC−8
D SUFFIX
1 PLASTIC PACKAGE
3423
ALYW
CASE 751
1
3423
A
L
Y
W
= Device Code
= Assembly Location
= Wafer Lot
= Year
= Work Week
PIN CONNECTIONS
VCC 1
Sense 1 2
Sense 2 3
Current
Source
4
8
Drive
Output
7 VEE
6
Indicator
Output
5
Remote
Activation
(Top View)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 7 of this data sheet.
© Semiconductor Components Industries, LLC, 2005
March, 2005 − Rev. 5
1
Publication Order Number:
MC3423/D
1 page  
MC3423
Power
Supply
#1
1
6
7
+ 30
R2 = 2.7 k
20
−
Typ
Max
Min
Power
Supply
#2
R1 10k
1
5
7
Q1
1.0k
Figure 8. Circuit Configuration for
Activating One MC3423 from Another
+
−
Note that both supplies have their negative output
leads tied together (i.e., both are positive supplies). If
their positive leads are common (two negative supplies)
the emitter of Q1 would be moved to the positive lead of
supply 1 and R1 would therefore have to be resized to
deliver the appropriate drive to Q1.
Crowbar SCR Considerations
Referring to Figure 11, it can be seen that the crowbar
SCR, when activated, is subject to a large current surge
from the output capacitance, Cout. This capacitance
consists of the power supply output caps, the load’s
decoupling caps, and in the case of Figure 11A, the supply’s
input filter caps. This surge current is illustrated in Figure
12, and can cause SCR failure or degradation by any one
of three mechanisms: di/dt, absolute peak surge, or I2t. The
interrelationship of these failure methods and the breadth
of the applications make specification of the SCR by the
semiconductor manufacturer difficult and expensive.
Therefore, the designer must empirically determine the
SCR and circuit elements which result in reliable and
effective OVP operation. However, an understanding of the
factors which influence the SCR’s di/dt and surge
capabilities simplifies this task.
di/dt
As the gate region of the SCR is driven on, its area of
conduction takes a finite amount of time to grow, starting
as a very small region and gradually spreading. Since the
anode current flows through this turned−on gate region,
very high current densities can occur in the gate region if
high anode currents appear quickly (di/dt). This can result
in immediate destruction of the SCR or gradual
degradation of its forward blocking voltage capabilities −
depending on the severity of the occasion.
10
0
0
5.0 10
15
20
25 30
VT, TRIP VOLTAGE (V)
Figure 9. R1 versus Trip Voltage
35
30
RG(min) = 0
if VCC < 11 V
25
20
15
10
0 10 20 30 40 50 60 70 80
RG, GATE CURRENT LIMITING RESISTOR (W)
Figure 10. Minimum RG versus Supply Voltage
1 23 57 1
1.0
0.1
0.01
0.001
0.0001
0.001
0.01 0.1
1.0
td, DELAY TIME (ms)
Figure 11. Capacitance versus
Minimum Overvoltage Duration
1
5
2
1
10
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5
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| Páginas | Total 10 Páginas | |
| PDF Descargar | [ Datasheet MC3423.PDF ] | |
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