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參數(shù)資料
| 型號(hào)： | LM25005MHX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 42V, 2.5A STEP-DOWN SWITCHING REGULATOR |
| 中文描述： | 4.25 A SWITCHING REGULATOR, 525 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封裝： | TSSOP-20 |
| 文件頁數(shù)： | 17/21頁 |
| 文件大?。?/td> | 756K |
| 代理商： | LM25005MHX |
Application Information
(Continued)
Components R4 and C5 configure the error amplifier as a
type II configuration which has a pole at DC and a zero at f
Z
= 1 / (2
π
R4C5). The error amplifier zero cancels the modu-
lator pole leaving a single pole response at the crossover
frequency of the loop gain. A single pole response at the
crossover frequency yields a very stable loop with 90 de-
grees of phase margin.
For the design example, a target loop bandwidth (crossover
frequency) of 20 kHz was selected. The compensation net-
work zero (f
Z
) should be selected at least an order of mag-
nitude less than the target crossover frequency. This con-
strains the product of R4 and C5 for a desired compensation
network zero 1 / (2
π
R4 C5) to be less than 2kHz. Increasing
R4 while proportionally decreasing C5, increases the error
amp gain. Conversely, decreasing R4 while proportionally
increasing C5, decreases the error amp gain. For the design
example C5 was selected for 0.01μF and R4 was selected
for 49.9 k
. These values configure the compensation net-
work zero at 320 Hz. The error amp gain at frequencies
greater than f
Z
is: R4 / R5, which is approximately 10 (20dB).
The overall loop can be predicted as the sum (in dB) of the
modulator gain and the error amp gain.
If a network analyzer is available, the modulator gain can be
measured and the error amplifier gain can be configured for
the desired loop transfer function. If a network analyzer is not
available, the error amplifier compensation components can
be designed with the guidelines given. Step load transient
tests can be performed to verify acceptable performance.
The step load goal is minimum overshoot with a damped
response. C6 can be added to the compensation network to
decrease noise susceptibility of the error amplifier. The value
of C6 must be sufficiently small since the addition of this
capacitor adds a pole in the error amplifier transfer function.
This pole must be well beyond the loop crossover frequency.
Agood approximation of the location of the pole added by C6
is: f
p2
= fz x C5 / C6.
20170015
FIGURE 8. Gain and Phase of Modulator
R
LOAD
= 5 Ohms and C
OUT
= 177 μF
20170016
FIGURE 9. Error Amplifier Gain and Phase
20170017
FIGURE 10. Overall Loop Gain and Phase
L
www.national.com
17
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM25005MHX/NOPB | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)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(fēng)格:SMD/SMT |
| LM25007 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Boot Capacitor Regulation in LM25007 Constant-On-Time (COT) Converter |
| LM25007_08 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:42V, 0.5A Step-Down Switching Regulator |
| LM25007_11 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Boot Capacitor Regulation in LM25007 Constant-On-Time (COT) Converter |
| LM25007EVAL | 功能描述:電源管理IC開發(fā)工具 LM25007 EVAL BOARD RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
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