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參數(shù)資料
| 型號： | MC7918 |
| 廠商： | Motorola, Inc. |
| 英文描述： | THREE-TERMINAL NEGATIVE FIXED VOLTAGE REGULATORS |
| 中文描述： | 三端負(fù)固定電壓調(diào)節(jié)器 |
| 文件頁數(shù)： | 9/12頁 |
| 文件大小： | 186K |
| 代理商： | MC7918 |
MC7900
9
MOTOROLA ANALOG IC DEVICE DATA
APPLICATIONS INFORMATION
Design Considerations
The MC7900 Series of fixed voltage regulators are
designed with Thermal overload Protection that shuts down
the circuit when subjected to an excessive power overload
condition. Internal Short Circuit Protection that limits the
maximum current the circuit will pass, and Output Transistor
Safe–Area Compensation that reduces the output short
circuit current as the voltage across the pass transistor is
increased.
In many low current applications, compensation
capacitors are not required. However, it is recommended that
the regulator input be bypassed with a capacitor if the
regulator is connected to the power supply filter with long wire
lengths, or if the output load capacitance is large. An input
bypass capacitor should be selected to provide good
high–frequency characteristics to insure stable operation
under all load conditions. A 0.33
μ
F or larger tantalum, mylar,
or other capacitor having low internal impedance at high
frequencies should be chosen. The capacitor chosen should
have an equivalent series resistance of less than 0.7
. The
bypass capacitor should be mounted with the shortest
possible leads directly across the regulators input terminals.
Normally good construction techniques should be used to
minimize ground loops and lead resistance drops since the
regulator has no external sense lead. Bypassing the output is
also recommended.
Figure 7. Current Regulator
The MC7905, –5.0 V regulator can be used as a constant current source when
connected as above. The output current is the sum of resistor R current and
quiescent bias current as follows.
The quiescent current for this regulator is typically 4.3 mA. The 5.0 V regulator was
chosen to minimize dissipation and to allow the output voltage to operate to within
6.0 V below the input voltage.
IO =
5.0 V
R
+ IB
–20 V
Input
MC7905
10
R
IO = 200 mA
–
VO
≤
10 V
1.0
μ
F
Gnd
Gnd
+1.0
μ
F
+
Figure 8. Current Boost Regulator
(–5.0 V @ 4.0 A, with 5.0 A Current Limiting)
When a boost transistor is used, short circuit currents are equal to the sum of the
series pass and regulator limits, which are measured at 3.2 A and 1.8 A respectively
in this case. Series pass limiting is approximately equal to 0.6 V/RSC. Operation
beyond this point to the peak current capability of the MC7905C is possible if the
regulator is mounted on a heatsink; otherwise thermal shutdown will occur when
the additional load current is picked up by the regulator.
*Mounted on heatsink.
–10
Input
V
0.56
0.56
0.56
MJE200*
or Equiv
5.6
2N3055*
or Equiv
MC7905*
1.0
μ
F
–5.0 V
Output
Gnd
Gnd
+
+
1.0
μ
F
10
μ
F+
Figure 9. Operational Amplifier Supply
(
±
15 @ 1.0 A)
The MC7815 and MC7915 positive and negative regulators may be connected as
shown to obtain a dual power supply for operational amplifiers. A clamp diode
should be used at the output of the MC7815 to prevent potential latch–up problems
whenever the output of the positive regulator (MC7815) is drawn below ground with
an output current greater than 200 mA.
+20 V
Input
+15 V
Output
0.33
μ
F
1N4001
or Equiv
Gnd
Gnd
1.0
μ
F
+
–20 V
Input
–15 V
Output
MC7815
MC7915
+
+
+
1.0
μ
F
1.0
μ
F
1.0
μ
F
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MC7918ACD2T | 制造商:MOTOROLA 制造商全稱:Motorola, Inc 功能描述:THREE-TERMINAL NEGATIVE FIXED VOLTAGE REGULATORS |
| MC7918ACT | 制造商:MOTOROLA 制造商全稱:Motorola, Inc 功能描述:THREE-TERMINAL NEGATIVE FIXED VOLTAGE REGULATORS |
| MC7918BD2T | 制造商:MOTOROLA 制造商全稱:Motorola, Inc 功能描述:THREE-TERMINAL NEGATIVE FIXED VOLTAGE REGULATORS |
| MC7918BT | 制造商:MOTOROLA 制造商全稱:Motorola, Inc 功能描述:THREE-TERMINAL NEGATIVE FIXED VOLTAGE REGULATORS |
| MC7918CD2T | 制造商:MOTOROLA 制造商全稱:Motorola, Inc 功能描述:THREE-TERMINAL NEGATIVE VOLTAGE REGULATORS |
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