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參數(shù)資料
| 型號： | MIC4721 |
| 廠商： | Micrel Semiconductor,Inc. |
| 英文描述： | Quad UART with 16-byte FIFO and infrared (IrDA) encoder/decoder, SOT315-1 (LQFP80), Reel Dry Pack, SMD, 13",Turned |
| 中文描述： | 1.5A的2MHz的集成開關(guān)降壓穩(wěn)壓器 |
| 文件頁數(shù)： | 13/19頁 |
| 文件大?。?/td> | 827K |
| 代理商： | MIC4721 |
Micrel, Inc.
MIC4721
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.
May 2007
13
M9999-052907-A
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 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, a 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.
The following Bode analysis show the small signal loop
stability of the MIC4721. The MIC4721 utilizes a type III
compensation. This is a dominant low frequency pole,
followed by 2 zero’s and finally the double pole of the
inductor capacitor filter, creating a final 20dB/decade roll
off. Bode analysis gives us a few important data points;
speed of response (Gain Bandwidth or GBW) and loop
stability. Loop speed or GBW determines the response
time to a load transient. Faster response times yield
smaller voltage deviations to load steps. Instability in a
control loop occurs when there is gain and positive
feedback. Phase margin is the measure of how stable
the given system is. It is measured by determining how
far the phase is from crossing zero when the gain is
equal to 1 (0dB).
Typically for 3.3V
IN
and 1.8V
OUT
at 1.5A;
Phase Margin = 47 Degrees
GBW = 156KHz
Gain will also increase with input voltage. The following
graph shows the increase in GBW for an increase in
supply voltage.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MIC4721YMM | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 1.5A 2MHz 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: 安裝風格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| MIC4721YMM TR | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 1.5A 2MHz 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: 安裝風格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| MIC4721YMMTR | 功能描述:IC REG BUCK ADJ 1.5A 10MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標準包裝:20 系列:SIMPLE SWITCHER® 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:12V 輸入電壓:4 V ~ 60 V PWM 型:電壓模式 頻率 - 開關(guān):52kHz 電流 - 輸出:1A 同步整流器:無 工作溫度:-40°C ~ 125°C 安裝類型:通孔 封裝/外殼:16-DIP（0.300"，7.62mm） 包裝:管件 供應(yīng)商設(shè)備封裝:16-DIP 其它名稱:*LM2575HVN-12LM2575HVN-12 |
| MIC4722 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:3mm x 3mm 2.7MHz 3A PWM Buck Regulator |
| MIC4722_10 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:3mm x 3mm 2.7MHz 3A PWM Buck Regulator |
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