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參數(shù)資料
| 型號(hào)： | LM1577K-883 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | SIMPLE SWITCHER-R Step-Up Voltage Regulator |
| 中文描述： | SIMPLE SWITCHER系列- R的升壓穩(wěn)壓器 |
| 文件頁(yè)數(shù)： | 20/27頁(yè) |
| 文件大?。?/td> | 870K |
| 代理商： | LM1577K-883 |
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Application Hints
(Continued)
C. Calculate the minimum value of C
C
D. Calculate the maximum ESR of the +V
OUT
and V
OUT
output capacitors in parallel.
This formula can also be used to calculate the maximum
ESR of a single output regulator.
At this point, refer to this same section in the
Step-Up Regu-
lator Design Procedure
for more information regarding the
selection of C
OUT
.
3. Output Voltage Selection
This section is for applications using the LM1577-ADJ/
LM2577-ADJ. Skip this section if the LM1577-12/LM2577-12
or LM1577-15/LM2577-15 is being used.
With the LM1577-ADJ/LM2577-ADJ, the output voltage is
given by
V
OUT
= 1.23V (1 + R1/R2)
Resistors R1 and R2 divide the output voltage down so it can
be compared with the LM1577-ADJ/LM2577-ADJ internal
1.23V reference. For a desired output voltage V
OUT
, select
R1 and R2 so that
4. Diode Selection
The switching diode in a flyback converter must withstand
the reverse voltage specified by the following equation.
A suitable diode must have a reverse voltage rating greater
than this. In addition it must be rated for more than the aver-
age and peak diode currents listed in Figure 19
5. Input Capacitor Selection
The primary of a flyback transformer draws discontinuous
pulses of current from the input supply. As a result, a flyback
regulator generates more noise at the input supply than a
step-up regulator, and this requires a larger bypass capacitor
to decouple the LM1577/LM2577 V
pin from this noise. For
most applications, a low ESR, 1.0 μF cap will be sufficient, if
it is connected very close to the V
IN
and Ground pins.
Duty Cycle
D
Primary Current Variation
I
P
Peak Primary Current
I
P(PK)
Switch Voltage when Off
V
SW(OFF)
Diode Reverse Voltage
Average Diode Current
Peak Diode Current
V
R
V
OUT+
N (V
IN
V
SAT
)
I
LOAD
I
D(AVE)
I
D(PK)
Short Circuit Diode Current
Power Dissipation of
LM1577/LM2577
P
D
DS011468-78
FIGURE 19. Flyback Regulator Formulas
www.national.com
20
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM1577KADJ | SIMPLE SWITCHER-R Step-Up Voltage Regulator |
| LM1771SMM | Low-Voltage Synchronous Buck Controller with Precision Enable and No External Compensation |
| LM1771 | Low-Voltage Synchronous Buck Controller with Precision Enable and No External Compensation |
| LM1771_0608 | Low-Voltage Synchronous Buck Controller with Precision Enable and No External Compensation |
| LM1771SMMX | Low-Voltage Synchronous Buck Controller with Precision Enable and No External Compensation |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM1577KADJ | 制造商:NSC 制造商全稱(chēng):National Semiconductor 功能描述:SIMPLE SWITCHER-R Step-Up Voltage Regulator |
| LM1577K-ADJ/883 | 制造商:Texas Instruments 功能描述:Conv DC-DC Single Step Up 3.5V to 40V 5-Pin(4+Tab) TO-3 Tray |
| LM1578 | 制造商:Texas Instruments 功能描述: |
| LM1578A | 制造商:NSC 制造商全稱(chēng):National Semiconductor 功能描述:Switching Regulator |
| LM1578AH/883 | 制造商:Rochester Electronics LLC 功能描述: |
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