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参数资料
| 型号： | MIC4744YTSE |
| 厂商： | Micrel Inc |
| 文件页数： | 14/23页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 2A DL 16TSSOP |
| 标准包装： | 94 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 2 |
| 输出电压： | 可调至 0.6V |
| 输入电压： | 2.9 V ~ 5.5 V |
| 频率 - 开关： | 4MHz |
| 电流 - 输出： | 2A |
| 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： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 16-EPAD TSSOP |
| 产品目录页面： | 1093 (CN2011-ZH PDF) |
| 其它名称： | 576-3357-5 |
Micrel, Inc.
Loop Stability and Bode Analysis
Bode Plot
MIC4744
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 transformer. Figure 7 demonstrates how a
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0
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Vin=3.6V Vout=1.8V Iout=2A
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0
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transformer is used to inject a signal into the feedback
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1000 10000 100000
FREQUENCY (Hz)
1000000
network.
Typically for 3.6Vin and 1.8Vout at 2A:
?
?
Phase Margin=80.7 Degrees
GBW=210KHz
Being that the MIC4744 is non-synchronous; the
regulator only has the ability to source current. This
means that the regulator has to rely on the load to be
able to sink current. This causes a non-linear response
at light loads. The following plot shows the effects of the
pole created by the nonlinearity of the output drive
during light load (discontinuous) conditions.
Figure 7. Transformer Injection
Bode Plot
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.
The following Bode analysis show the small signal loop
stability of the MIC4744, it utilizes type III compensation.
This is a dominant low frequency pole, followed by 2
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Vin=3.6V Vout=1.8V Iout=0.1A
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zeros and finally the double pole of the inductor
capacitor filter, creating a final 20dB/decade roll off.
-30
100
1000 10000 100000
FREQUENCY (Hz)
-105
1000000
Bode analysis gives us a few important data points;
speed of response (Gain Bandwidth or GBW) and loop
3.6Vin, 1.8Vout Iout=0.1A:
stability. Loop speed or GBW determines the response
time to a load transient. Faster response times yield
smaller voltage deviations to load steps.
?
?
Phase Margin=68.3 Degrees
GBW= 24.0kHz
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).
Feed Forward Capacitor
The feedback resistors are a gain reduction block in the
overall system response of the regulator. By placing a
capacitor from the output to the feedback pin, high
frequency signal can bypass the resistor divider, causing
a gain increase up to unity gain.
March 2009
14
M9999-030209-C
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| MIC4782YML | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:1.8 MHz Dual 2A Integrated Switch Buck Regulator |
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| MIC4782YML-TR | 功能描述:Buck Switching Regulator IC Positive Adjustable 0.6V 2 Output 2A 16-VFQFN Exposed Pad, 16-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:2 电压 - 输入（最小值）:3V 电压 - 输入（最大值）:6V 电压 - 输出（最小值/固定）:0.6V 电压 - 输出（最大值）:6V 电流 - 输出:2A 频率 - 开关:1.8MHz 同步整流器:无 工作温度:-20°C ~ 125°C（TJ） 安装类型:表面贴装 封装/外壳:16-VFQFN 裸露焊盘，16-MLF? 供应商器件封装:16-MLF?（4x4） 标准包装:1 |
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