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參數(shù)資料
| 型號： | LM2577SADJ |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 6 A SWITCHING REGULATOR, 62 kHz SWITCHING FREQ-MAX, PSSO5 |
| 封裝： | TO-263, 5 PIN |
| 文件頁數(shù)： | 10/31頁 |
| 文件大?。?/td> | 1406K |
| 代理商： | LM2577SADJ |
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Application Hints (Continued)
2. Compensation Network (R
C,CC) and Output Capacitor
(C
OUT) Selection
R
C and CC form a pole-zero compensation network that
stabilizes the regulator. The values of R
C and CC are mainly
dependant on the regulator voltage gain, I
LOAD(max), L and
C
OUT. The following procedure calculates values for RC,CC,
and C
OUT that ensure regulator stability. Be aware that this
procedure doesn’t necessarily result in R
C and CC that pro-
vide optimum compensation. In order to guarantee optimum
compensation, one of the standard procedures for testing
loop stability must be used, such as measuring V
OUT tran-
sient response when pulsing I
LOAD (see Figure 15).
A. First, calculate the maximum value for R
C.
Select a resistor less than or equal to this value, and it
should also be no greater than 3 k
.
B. Calculate the minimum value for C
OUT using the following
two equations.
The larger of these two values is the minimum value that
ensures stability.
C. Calculate the minimum value of C
C .
The compensation capacitor is also part of the soft start
circuitry. When power to the regulator is turned on, the
switch duty cycle is allowed to rise at a rate controlled by this
capacitor (with no control on the duty cycle, it would imme-
diately rise to 90%, drawing huge currents from the input
power supply). In order to operate properly, the soft start
circuit requires C
C
≥ 0.22 F.
The value of the output filter capacitor is normally large
enough to require the use of aluminum electrolytic capaci-
tors. Figure 11 lists several different types that are recom-
mended for switching regulators, and the following param-
eters are used to select the proper capacitor.
Working Voltage (WVDC): Choose a capacitor with a work-
ing voltage at least 20% higher than the regulator output
voltage.
Ripple Current: This is the maximum RMS value of current
that charges the capacitor during each switching cycle. For
step-up and flyback regulators, the formula for ripple current
is
Choose a capacitor that is rated at least 50% higher than this
value at 52 kHz.
Equivalent Series Resistance (ESR) : This is the primary
cause of output ripple voltage, and it also affects the values
of R
C and CC needed to stabilize the regulator. As a result,
the preceding calculations for C
C and RC are only valid if
ESR doesn’t exceed the maximum value specified by the
following equations.
Select a capacitor with ESR, at 52 kHz, that is less than or
equal to the lower value calculated. Most electrolytic capaci-
tors specify ESR at 120 Hz which is 15% to 30% higher than
at 52 kHz. Also, be aware that ESR increases by a factor of
2 when operating at 20C.
In general, low values of ESR are achieved by using large
value capacitors (C
≥ 470 F), and capacitors with high
WVDC, or by paralleling smaller-value capacitors.
Inductor
Manufacturer’s Part Number
Code
Schott
Pulse
Renco
L47
67126980
PE - 53112
RL2442
L68
67126990
PE - 92114
RL2443
L100
67127000
PE - 92108
RL2444
L150
67127010
PE - 53113
RL1954
L220
67127020
PE - 52626
RL1953
L330
67127030
PE - 52627
RL1952
L470
67127040
PE - 53114
RL1951
L680
67127050
PE - 52629
RL1950
H150
67127060
PE - 53115
RL2445
H220
67127070
PE - 53116
RL2446
H330
67127080
PE - 53117
RL2447
H470
67127090
PE - 53118
RL1961
H680
67127100
PE - 53119
RL1960
H1000
67127110
PE - 53120
RL1959
H1500
67127120
PE - 53121
RL1958
H2200
67127130
PE - 53122
RL2448
Schott Corp., (612) 475-1173
1000 Parkers Lake Rd., Wayzata, MN 55391
Pulse Engineering, (619) 268-2400
P.O. Box 12235, San Diego, CA 92112
Renco Electronics Inc., (516) 586-5566
60 Jeffryn Blvd. East, Deer Park, NY 11729
FIGURE 10. Table of Standardized Inductors and
Manufacturer’s Part Numbers
LM1577/LM2577
www.national.com
18
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LM2577S-ADJ | 功能描述:直流/直流開關轉換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
| LM2577S-ADJ/NOPB | 功能描述:直流/直流開關轉換器 STEP-UP VLTG REG RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
| LM2577S-ADJ/NOPB | 制造商:Texas Instruments 功能描述:DC/DC Converter (DC-DC) / Switching Regu |
| LM2577SX-12 | 功能描述:直流/直流開關轉換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
| LM2577SX-12/NOPB | 功能描述:直流/直流開關轉換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
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