参数资料
| 型号： | MIC4721YMMTR |
| 厂商： | Micrel Inc |
| 文件页数： | 13/19页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 1.5A 10MSOP |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 可调至 1V |
| 输入电压： | 2.7 V ~ 5.5 V |
| 频率 - 开关： | 2MHz |
| 电流 - 输出： | 1.5A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 10-MSOP |
| 其它名称： | MIC4721YMM TR |
Micrel, Inc.
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.
MIC4721
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).
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
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.
May 2007
13
M9999-052907-A
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| MIC4722YML TR | 功能描述:直流/直流开关调节器 3mm X 3mm 2.7MHz 3A PWM Buck Regulator RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体: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:- 包装:剪切带（CT） 零件状态:停产 功能:降压 输出配置:正 拓扑:降压 输出类型:可调式 输出数:1 电压 - 输入（最小值）:2.7V 电压 - 输入（最大值）:5.5V 电压 - 输出（最小值/固定）:1V 电压 - 输出（最大值）:5.5V 电流 - 输出:3A 频率 - 开关:2.7MHz 同步整流器:无 工作温度:-40°C ~ 125°C （TJ） 安装类型:表面贴装 封装/外壳:12-VFDFN 裸焊盘，12-MLF? 供应商器件封装:12-MLF?（4x4） 标准包装:1 |
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