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PDF SC431A Data sheet ( Hoja de datos )
| Número de pieza | SC431A | |
| Descripción | Programmable Precision References | |
| Fabricantes | ON Semiconductor | |
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NCP431A, SC431A,
NCP431B, NCP432B Series
Programmable Precision
References
The NCP431/NCP432 integrated circuits are three−terminal
programmable shunt regulator diodes. These monolithic IC voltage
references operate as a low temperature coefficient zener which is
programmable from Vref to 36 V using two external resistors. These
devices exhibit a wide operating current range of 40 mA to 100 mA
with a typical dynamic impedance of 0.22 W. The characteristics of
these references make them excellent replacements for zener diodes in
many applications such as digital voltmeters, power supplies, and op
amp circuitry. The 2.5 V reference makes it convenient to obtain a
stable reference from 5.0 V logic supplies, and since the NCP431/
NCP432 operates as a shunt regulator, it can be used as either a
positive or negative voltage reference. Low minimum operating
current makes this device an ideal choice for secondary regulators in
SMPS adapters with extremely low no−load consumption.
Features
• Programmable Output Voltage to 36 V
• Low Minimum Operating Current: 40 mA, Typ @ 25°C
• Voltage Reference Tolerance: ±0.5%, Typ @ 25°C
(NCP431B/NCP432B)
• Low Dynamic Output Impedance, 0.22 W Typical
• Sink Current Capability of 40 mA to 100 mA
• Equivalent Full−Range Temperature Coefficient of 50 ppm/°C
Typical
• Temperature Compensated for Operation over Full Rated Operating
Temperature Range
• SC Prefix for Automotive and Other Applications Requiring Unique
Site and Control Change Requirements; AEC−Q100 Qualified and
PPAP Capable
• These are Pb−Free Devices
Typical Applications
• Voltage Adapters
• Switching Power Supply
• Precision Voltage Reference
• Charger
• Instrumentation
http://onsemi.com
TO−92
LP SUFFIX
CASE 29−11
Pin 1. Reference
2. Anode
1 2 3 3. Cathode
8
1
Cathode
Anode
Anode
NC
SOIC−8 NB
D SUFFIX
CASE 751
1
(Top View)
Reference
Anode
Anode
NC
3
1
2
NCP431
Pin 1. Reference
2. Cathode
3. Anode
SOT−23−3
SN SUFFIX
CASE 318
NCP432
Pin 1. Cathode
2. Reference
3. Anode
ORDERING AND MARKING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 13 of this data sheet.
© Semiconductor Components Industries, LLC, 2013
February, 2013 − Rev. 4
1
Publication Order Number:
NCP431/D
Free Datasheet http://www.datasheet4u.com/
1 page  
NCP431A, SC431A, NCP431B, NCP432B Series
Input
Vref
V KA
IK
Input
R1
Iref
R2 Vref
VKA
Input
IK
ǒ ǓVKA
+ Vref
1
)
R1
R2
) Iref @ R1
V KA
Ioff
Figure 3. Test Circuit for VKA = Vref
Figure 4. Test Circuit for VKA > Vref Figure 5. Test Circuit for Ioff
150.0
Input
100.0
VKA = Vref
TA = 25°C
VKA
IK
50.0
0.0
−50.0
60.0
40.0
20.0
Input
VKA = Vref
TA = 25°C
VKA
IK
0.0
−20.0
−40.0
IMin
−100.0−1.0
0.0
1.0
2.0
3.0
VKA, CATHODE VOLTAGE (V)
Figure 6. Cathode Current versus Cathode
Voltage
−60.0
−1.0 0.0 1.0 2.0 3.0
VKA, CATHODE VOLTAGE (V)
Figure 7. Cathode Current versus Cathode
Voltage
2540
2530
Input
2520
2510
Vref
VKA
IK
VKA = Vref
IK = 1 mA
2500
2490
2480
2470
2460−50 −25
0
25 50 75 100
TA, AMBIENT TEMPERATURE (°C)
Figure 8. Reference Input Voltage versus
Ambient temperature
125
120
110
100
90
Input IK = 1 mA VKA
220k
Iref
IK
80
70
60
50
4−050 −25
0
25 50 75 100 125
TA, AMBIENT TEMPERATURE (°C)
Figure 9. Reference Input Current versus
Ambient temperature
http://onsemi.com
5
Free Datasheet http://www.datasheet4u.com/
5 Page 
NCP431A, SC431A, NCP431B, NCP432B Series
Figure 32. Simplified NCP431/NCP432 Device Model
NCP431/NCP432 OPEN−LOOP VOLTAGE GAIN
VERSUS FREQUENCY
Note that the crossover frequency in this case is about
250 kHz, having a phase margin of about −46°. Therefore,
instability of this circuit is likely.
NCP431/NCP432 OPEN−LOOP BODE PLOT WITH
LOAD CAP
Figure 33. Example 1 Circuit Open Loop Gain Plot
Example 2.
IC = 7.5 mA, RL = 2.2 kW, CL = 0.01 mF. Cathode tied to
reference input pin. An examination of the data sheet
stability boundary curve (Figure 17) shows that this value of
load capacitance and cathode current is on the boundary.
Define the transfer gain.
The DC gain is:
G + GMRGMGoRL + (2.138)(1.0M)(1.25m)(230)
+ 6389 + 76 dB
The resulting open loop Bode plot is shown in Figure 34.
The asymptotic plot may be expressed as the following
equation:
Av + 615
ǒ Ǔ1
)
jf
500 kHz
ǒ Ǔǒ Ǔǒ Ǔ1
)
jf
8.0 kHz
1
)
60
jf
kHz
1
)
jf
7.2 kHz
Note that the transfer function now has an extra pole
formed by the load capacitance and load resistance.
Figure 34. Example 2 Circuit Open Loop Gain Plot
With three poles, this system is unstable. The only hope
for stabilizing this circuit is to add a zero. However, that can
only be done by adding a series resistance to the output
capacitance, which will reduce its effectiveness as a noise
filter. Therefore, practically, in reference voltage
applications, the best solution appears to be to use a smaller
value of capacitance in low noise applications or a very large
value to provide noise filtering and a dominant pole rolloff
of the system.
The NCP431/NCP432 is often used as a regulator in
secondary side of a switch mode power supply (SMPS).
The benefit of this reference is high and stable gain under
low bias currents. Figure 35 shows dependence of the gain
(dynamic impedance) on the bias current. Value of
http://onsemi.com
11
Free Datasheet http://www.datasheet4u.com/
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet SC431A.PDF ] | |
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