参数资料
| 型号： | MIC2169BYMME |
| 厂商： | Micrel Inc |
| 文件页数： | 15/25页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM VM 10-MSOP |
| 特色产品： | MIC2169B Buck Control IC |
| 标准包装： | 100 |
| PWM 型： | 电压模式 |
| 输出数： | 1 |
| 频率 - 最大： | 550kHz |
| 占空比： | 92% |
| 电源电压： | 3 V ~ 14.5 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 |
| 包装： | 管件 |
| 产品目录页面： | 1092 (CN2011-ZH PDF) |
| 其它名称： | 576-3545-5 |
? ?
Error Amplifier (z) = gm × ?
?
? s × ( C1 + C2 ) × ? ? 1 + s × R1 × C1 × C2 ? ? ?
Error Amplifier (z) = gm × ?
? s × C1 × (1 + s × R1 × C2) ?
Micrel, Inc.
It can be seen from Figure 9 that at 50kHz, the phase is
approximately –90° versus Figure 10 where the number
is –150°. This means that the transconductance error
amplifier has to provide a phase boost of about 45° to
achieve a closed loop phase margin of 45° at a
crossover frequency of 50kHz for Figure 9, versus 105°
for Figure 10. The simple RC and C2 compensation
scheme allows a maximum error amplifier phase boost
of about 90°. Therefore, it is easier to stabilize the
MIC2169B voltage control loop by using high-ESR value
output capacitors.
g m Error Amplifier
It is undesirable to have high error amplifier gain at high
frequencies because high frequency noise spikes would
be picked up and transmitted at large amplitude to the
output, thus, gain should be permitted to fall off at high
frequencies. At low frequency, it is desired to have high
open-loop gain to attenuate the power line ripple. Thus,
the error amplifier gain should be allowed to increase
rapidly at low frequencies.
The transfer function with R1, C1, and C2 for the internal
g m error amplifier can be approximated by the following
equation:
? ?
1 + s × R1 × C1
? ?
? ? C1 + C2 ? ?
The above equation can be simplified by assuming
C2<<C1,
? 1 + s × R1 × C1 ?
?
From the above transfer function, one can see that R1
and C1 introduce a zero and R1 and C2 a pole at the
following frequencies:
F ZERO = 1/2 π × R1 × C1
F POLE = 1/2 π × C2 × R1
F POLE@origin = 1/2 π × C1
Figures 11 and 12 show the gain and phase curves for
the above transfer function with R1 = 4.02k, C1 = 100nF,
C2 = 150pF, and gm = 1.1m Ω –1 .
MIC2169B
Figure 11. Error Amplifier Gain Curve
Figure 12. Error Amplifier Phase Curve
Total Open-Loop Response
The open-loop response for the MIC2169B controller is
easily obtained by adding the power path and the error
amplifier gains together, since they already are in Log
scale. It is desirable to have the gain curve intersect zero
dB at tens of kilohertz, this is commonly called crossover
frequency; the phase margin at crossover frequency
should be at least 45°. Phase margins of 30° or less
cause the power supply to have substantial ringing when
subjected to transients, and have little tolerance for
component or environmental variations.
Figures 13 and 14 show the open-loop gain and phase
margin for the 5V input and 1.8V output application, and
it can be seen from Figure 13 that the gain curve
intersects the 0dB at approximately 50kHz, and from
Figure 14 that at 50kHz, the phase shows approximately
74° of margin.
April 2010
15
M9999-041210-B
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| MIC2169BYMME TR | 功能描述:直流/直流开关转换器 Synchronous Step Down Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MIC2169MM | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:500 KHZ PWM SYNCHRONOUS BUCK CONTROL IC |
| MIC2169YMM | 功能描述:直流/直流开关调节器 Replaced by MIC2169AYMM (Lead Free) 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 |
| MIC2169YMM TR | 功能描述:直流/直流开关调节器 Replaced by MIC2169AYMM TR (Lead Free) 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 |
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