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參數(shù)資料
| 型號： | MIC4722YML |
| 廠商： | MICREL INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 3mm x 3mm 2.7MHz 3A PWM Buck Regulator |
| 中文描述： | 11 A SWITCHING REGULATOR, 3000 kHz SWITCHING FREQ-MAX, DSO12 |
| 封裝： | 3 X 3 MM, LEAD FREE, MLF-12 |
| 文件頁數(shù)： | 13/20頁 |
| 文件大小： | 581K |
| 代理商： | MIC4722YML |
Micrel, Inc.
MIC4722
Loop Stability and Bode Analysis
Bode analysis is an excellent way to measure small
signal stability and loop response in power supply
designs. Bode analysis monitors gain and phase of a
control loop. This is done by breaking the feedback loop
and injecting a signal into the feedback node and
comparing the injected signal to the output signal of the
control loop. This will require a network analyzer to
sweep the frequency and compare the injected signal to
the output signal. The most common method of injection
is the use of a transformer. Figure 7 demonstrates how a
transformer is used to inject a signal into the feedback
network.
September 2007
13
M9999-090507-B
Figure 7. Transformer Injection
A 50
resistor allows impedance matching from the
network analyzer source. This method allows the DC
loop to maintain regulation and allow the network
analyzer to insert an AC signal on top of the DC voltage.
The network analyzer will then sweep the source while
monitoring A and R for an A/R measurement. While this
is the most common method for measuring the gain and
phase of a power supply, it does have significant
limitations. First, to measure low frequency gain and
phase, the transformer needs to be high in inductance.
This makes frequencies <100Hz require an extremely
large and expensive transformer. Conversely, it must be
able to inject high frequencies. Transformers with these
wide frequency ranges generally need to be custom
made and are extremely expensive (usually to the tune
of several hundred dollars!). By using an op-amp, cost
and frequency limitations caused by an injection
transformer are completely eliminated. Figure 8
demonstrates using an op-amp in a summing amplifier
configuration for signal injection.
Network Analyzer
Source
+8V
R1
1k
R3
1k
R4
1k
50
Feedback
Output
Network
Analyzer
“A” Input
Network
Analyzer
“R” Input
MIC922BC5
Figure 8. Op Amp Injection
R1 and R2 reduce the DC voltage from the output to the
non-inverting input by half. The network analyzer is
generally a 50
source. R1 and R2 also divide the AC
signal sourced by the network analyzer by half. These
two signals are “summed” together at half of their
original input. The output is then amplified by 2 by R3
and R4 (the 50
is to balance the network analyzer’s
source impedance) and sent to the feedback signal. This
essentially breaks the loop and injects the AC signal on
top of the DC output voltage and sends it to the
feedback. By monitoring the feedback “R” and output
“A”, gain and phase are measured. This method has no
minimum frequency. Ensure that the bandwidth of the
op-amp being used is much greater than the expected
bandwidth of the power supply’s control loop. An op-amp
with >100MHz bandwidth is more than sufficient for most
power supplies (which includes both linear and
switching) and are more common and significantly
cheaper than the injection transformers previously
mentioned. The one disadvantage to using the op-amp
injection method; is that the supply voltages need to be
below the maximum operating voltage of the op-amp.
Also, the maximum output voltage for driving 50
inputs
using the MIC922 is 3V. For measuring higher output
voltages, 1M
input impedance is required for the A and
R channels. Remember to always measure the output
voltage with an oscilloscope to ensure the measurement
is working properly. You should see a single sweeping
sinusoidal waveform without distortion on the output. If
there is distortion of the sinusoid, reduce the amplitude
of the source signal. You could be overdriving the
feedback causing a large signal response.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MIC4722YML TR | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 3mm X 3mm 2.7MHz 3A PWM Buck Regulator RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| MIC4722YML-TR | 功能描述:Buck Switching Regulator IC Positive Adjustable 1V 1 Output 3A 12-VFDFN Exposed Pad, 12-MLF? 制造商:microchip technology 系列:- 包裝:剪切帶（CT） 零件狀態(tài):停產(chǎn) 功能:降壓 輸出配置:正 拓?fù)?降壓 輸出類型:可調(diào)式 輸出數(shù):1 電壓 - 輸入（最小值）:2.7V 電壓 - 輸入（最大值）:5.5V 電壓 - 輸出（最小值/固定）:1V 電壓 - 輸出（最大值）:5.5V 電流 - 輸出:3A 頻率 - 開關(guān):2.7MHz 同步整流器:無 工作溫度:-40°C ~ 125°C （TJ） 安裝類型:表面貼裝 封裝/外殼:12-VFDFN 裸焊盤，12-MLF? 供應(yīng)商器件封裝:12-MLF?（4x4） 標(biāo)準(zhǔn)包裝:1 |
| MIC4723 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:3A 2MHz Integrated Switch Buck Regulator |
| MIC4723_08 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:3A 2MHz Integrated Switch Buck Regulator |
| MIC4723YML | 制造商:Rochester Electronics LLC 功能描述: 制造商:RF Micro Devices Inc 功能描述: |
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