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参数资料
| 型号： | MIC2155YML TR |
| 厂商： | Micrel Inc |
| 文件页数： | 30/35页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM VM 32MLF |
| 特色产品： | MIC2155/6 Buck Control IC |
| 标准包装： | 1 |
| PWM 型： | 电压模式 |
| 输出数： | 1 |
| 频率 - 最大： | 550kHz |
| 占空比： | 80% |
| 电源电压： | 4.5 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 ~ 125°C |
| 封装/外壳： | 32-VFQFN 裸露焊盘，32-MLF? |
| 包装： | 标准包装 |
| 产品目录页面： | 1091 (CN2011-ZH PDF) |
| 其它名称： | 576-3527-6 |
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Micrel, Inc.
MIC2155/2156
Z 0 =
1
2 ? π ? R 1 ? C 2
Z2
2 . π . ( R1
1
R3 ) . C3
P1
2 . π .
1
C2 . C1 .
C2 C1
R2
Step 3: Determine the gain boost needed at the
crossover frequency (fc)
Typically, 50° of phase margin can be used for most
applications. This is a good tradeoff between an
overdamped system (slower response to transients) and
an underdamped system (overshoot or unstable
20 . log
R2
R1
response to transients). It also allows some margin for
component tolerances and variations due to ambient
Z1
1
2 . π . R2 . C2
P2
1
2 . π . R3 . C3
temperature changes. The phase margin at the
crossover frequency (fc) can be determined by plotting
the G VD (s) phase on a bode plot or can be estimated
with the following formula:
? ?
?
?
? + tan ? 1 ? fc ?
= tan ?
? 1 ? ? ? fc ? ? ?
? M
fc
? 1 ? Q × fo
? ?
? ? fo ? ?
? ?
2 ? ? fz ?
Figure 26. Type III Error Amplifier Gain/Phase
Error Amplifier Design Procedure
Step 1: Decide on the crossover frequency
To maximize transient response, the open loop
bandwidth should be made reasonably high. Initially, the
bandwidth can be selected to be 1/10 of the output
switching frequency. This may be improved once the
design is built and measurements are made. An initial
The additional phase boost required from the error
amplifier is:
? Boost = 52 ° ? ? M
Step 4: Determine the frequencies fz2 and fp1
The frequencies for the zero and pole (fz2 and fp1) are
calculated for the desired amount of phase boost at the
crossover frequency (fc):
bandwidth of 100kHz for the 2155 and 60kHz for the
2156 are good choices.
Step 2: Determine the gain required at the crossover
frequency
G Boost is how much gain boost is needed so the open
loop transfer function crosses 0dB at the pre-determined
fz 2 = fc ×
fp 1 = fc ×
1 ? sin [ ? Boost ]
1 + sin [ ? Boost ]
1 + sin [ ? Boost ]
1 ? sin [ ? Boost ]
crossover frequency. This can be measured by plotting
the G VD (s) transfer function or can be estimated with the
following formula:
Step 5: Determine the frequency for fz1
The low-frequency zero, fz1, is initially set to one-fifth of
the LC resonant frequency. If it is set too low, it will force
H × V IN ? fo ?
? fc ?
G Boost =
V M ? fc ? ? fz ?
× ? ? × ? ?
1
2
the low frequency gain to be low and impact transient
response. If set too high, it will not add enough phase
boost at the LC resonant frequency. This could cause
conditional stability, which when the phase drops below -
180° before the gain crosses 0dB. If the DC gain should
drop in this situation, this may lead to an unstable
Where: fo = LC filter resonant frequency
fc= open loop bandwidth chosen in Step 1
system.
fz = zero formed by C OUT and its ESR
H = voltage divider attenuation
V M =amplitude of the internal sawtooth ramp (V M =1)
V IN = Input voltage to the power supply
November 2009
30
fz 2 =
fo
5
M9999-111209-B
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| MIC2156YML-TR | 功能描述:Buck Regulator Positive Output Step-Down DC-DC Controller IC 32-MLF? (5x5) 制造商:microchip technology 系列:- 包装:剪切带（CT） 零件状态:过期 输出类型:晶体管驱动器 功能:降压 输出配置:正 拓扑:降压 输出数:2 输出阶段:2 电压 - 电源（Vcc/Vdd）:4.5 V ~ 14.5 V 频率 - 开关:300kHz 占空比（最大）:0.8 同步整流器:是 时钟同步:是 串行接口:- 控制特性:限流，使能，电源良好，软启动 工作温度:-40°C ~ 125°C （TJ） 封装/外壳:32-VFQFN 裸露焊盘，32-MLF? 供应商器件封装:32-MLF?（5x5） 标准包装:1 |
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