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PDF MC3423 Data sheet ( Hoja de datos )
| Número de pieza | MC3423 | |
| Descripción | OVERVOLTAGE SENSING CIRCUIT | |
| Fabricantes | Motorola Semiconductors | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MC3423 (archivo pdf) en la parte inferior de esta página. Total 8 Páginas | ||
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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.
MAXIMUM RATINGS
Rating
Differential Power Supply Voltage
Sense Voltage (1)
Sense Voltage (2)
Remote Activation Input Voltage
Output Current
Operating Ambient Temperature Range
Operating Junction Temperature
Storage Temperature Range
Symbol
VCC–VEE
VSense1
VSense2
Vact
IO
TA
TJ
Tstg
Value
40
6.5
6.5
7.0
300
0 to +70
125
–65 to +150
Unit
Vdc
Vdc
Vdc
Vdc
mA
°C
°C
°C
Order this document by MC3423/D
MC3423
OVERVOLTAGE
SENSING CIRCUIT
SEMICONDUCTOR
TECHNICAL DATA
8
1
P1 SUFFIX
PLASTIC PACKAGE
CASE 626
8
1
D SUFFIX
PLASTIC PACKAGE
CASE 751
(SOP–8)
PIN CONNECTIONS
Simplified Application
Vin
Current
Limited
DC
Power
Supply
+
Cout
O. V. P.
MC3423
MOTOROLA ANALOG IC DEVICE DATA
VCC 1
8
Drive
Output
Sense 1 2
7 VEE
Sense 2 3
6
Indicator
Output
Vout
Current
Source
4
5
Remote
Activation
(Top View)
ORDERING INFORMATION
Device
Operating
Temperature Range
Package
MC3423D
MC3423P1
TA = 0° to +70°C
SO–8
Plastic DIP
© Motorola, Inc. 1996
Rev 1
1
1 page  
MC3423
Figure 7. Circuit Configuration for
Activating One MC3423 from Another
Figure 8. R1 versus Trip Voltage
30
Power
Supply
#1
1
6
7
+
–
Power
Supply
#2
R1 10k
1
5
7
Q1
1.0k
+
–
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.
R2 = 2.7 k
20
10
Typ
Max
Min
0
0
5.0 10
15
20
25 30
VT, TRIP VOLTAGE (V)
Figure 9. Minimum RG versus Supply Voltage
35
30
RG(min) = 0
if VCC < 11 V
25
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.
20
15
10
0 10 20 30 40 50 60 70 80
RG, GATE CURRENT LIMITING RESISTOR (Ω)
Figure 10. Capacitance versus
Minimum Overvoltage Duration
1 2 3 57 1
1.0
0.1
0.01
0.001
0.0001
0.001
0.01 0.1
1.0
td, DELAY TIME (ms)
1
5
2
1
10
MOTOROLA ANALOG IC DEVICE DATA
5
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet MC3423.PDF ] | |
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