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参数资料
| 型号： | MIC2174C-1YMM TR |
| 厂商： | Micrel Inc |
| 文件页数： | 11/27页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM 10-MSOP |
| 标准包装： | 2,500 |
| 系列： | Hyper Speed Control™ |
| PWM 型： | 混合物 |
| 输出数： | 1 |
| 频率 - 最大： | 338kHz |
| 占空比： | 87% |
| 电源电压： | 3 V ~ 40 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： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽） |
| 包装： | 带卷 (TR) |
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Micrel, Inc.
Functional Description
The MIC2174/MIC2174C is an adaptive on-time
MIC2174/MIC2174C
The maximum duty cycle is obtained from the 363ns
T OFF(min) :
synchronous buck controller built for low cost and high
performance. It is designed for a wide input voltage
range from 3V to 40V and for high output power buck
converters. An estimated-ON-time method is applied in
Dmax =
T S ? T OFF(min)
T S
= 1 ?
363ns
T S
MIC2174/MIC2174C to obtain a constant switching
frequency and to simplify the control compensation. The
over-current protection is implemented without the use of
an external sense resistor. It includes an internal soft-
start function which reduces the power supply input
surge current at start-up by controlling the output voltage
rise time.
Theory of Operation
The MIC2174/MIC2174C is an adaptive on-time
synchronous buck controller. Further, Figure 1 illustrates
the block diagram for the control loop. The output
voltage variation will be sensed by the
MIC2174/MIC2174C feedback pin FB via the voltage
divider R1 and R2, and compared to a 0.8V reference
voltage V REF at the error comparator through a low gain
transconductance (gm) amplifier, which improves the
MIC2174/MIC2174C converter output voltage regulation.
If the FB voltage decreases and the output of the gm
where Ts = 1/300kHz = 3.33 μ s. It is not recommended to
use MIC2174/MIC2174C with a OFF-time close to
T OFF(min) during steady-state operation. Also, as V OUT
increases, the internal ripple injection will increase and
reduce the line regulation performance. Therefore, the
maximum output voltage of the MIC2174 should be
limited to 5.5V for up to 28V V HSD and 3.6V for V HSD
higher than 28V. If a higher output voltage is required,
use the MIC2176 instead. Please refer to “Setting Output
Voltage” subsection in “Application Information” for more
details.
The power stage input voltage V HSD is fed into the Fixed
T ON Estimation block through a 6:1 divider and 5V
voltage clamper. Therefore, if the V HSD is higher than
30V, then the Fixed T ON Estimation block uses 30V to
estimate T ON instead of the real V HSD . As a result, the
switching frequency will be less than 300kHz:
amplifier is below 0.8V, then the error comparator will
trigger the control logic and generate an ON-time period,
where in DH pin is logic high and DL pin is logic low. The
ON-time period length is predetermined by the “FIXED
f SW(VHDS > 30V) =
30V
V HSD
× 300kHz
(2)
T ON ESTIMATION” circuitry:
The estimated ON-time method results in a constant
T ON(estimat ed) =
V OUT
V HSD × 300kHz
(1)
300kHz switching frequency up to 30V V HSD . The actual
ON-time varies with the different rising and falling times
of the external MOSFETs. Therefore, the type of the
external MOSFETs, the output load current, and the
where V OUT is the output voltage, V HSD is the power
stage input voltage.
After an ON-time period, the MIC2174/MIC2174C goes
into the OFF-time period. This is when the DH pin is
logic low and DL pin is logic high. The OFF-time period
length depends upon the FB voltage in most cases.
When the FB voltage decreases and the output of the
gm amplifier is below 0.8V, then the ON-time period is
triggered and the OFF-time period ends. If the OFF-time
period determined by the FB voltage is less than the
minimum OFF time T OFF(min) , which is about 363ns
typical, then the MIC2174/MIC2174C control logic will
apply the T OFF(min) instead. T OFF(min) is required to
maintain enough energy in the Boost capacitor (C BST ) to
drive the high-side MOSFET.
control circuitry power supply V IN will modify the actual
ON-time and the switching frequency. Also, the minimum
T ON results in a lower switching frequency in high V HSD
and low V OUT applications, such as 36V to 1.0V. The
minimum T ON measured on the MIC2174/MIC2174C
evaluation board with Si7148DP MOSFETs is about
184ns. During the load transient, the switching frequency
is changed due to the varying OFF time.
To illustrate the control loop, the steady-state scenario
and the load transient scenario are analyzed. For easy
analysis, the gain of the gm amplifier is assumed to be 1.
With this assumption, the inverting input of the error
comparator is the same as the FB voltage. Figure 2
shows the MIC2174/MIC2174C control loop timing
during steady-state operation. During steady-state, the
gm amplifier senses the FB voltage ripple, which is
proportional to the output voltage ripple and the inductor
current ripple, to trigger the ON-time period. The ON-
time is predetermined by the estimation. The ending of
OFF-time is controlled by the FB voltage. At the valley of
September 2010
11
M9999-091310-C
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2176-1 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:Wide Input Voltage, Synchronous Buck Controllers Featuring Adaptive On-Time Control |
| MIC2176-1YMM | 功能描述:DC/DC 开关控制器 76V Synchronous Buck Controller RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MIC2176-1YMM TR | 功能描述:DC/DC 开关控制器 76V Synchronous Buck Controller RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MIC2176-2 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:Wide Input Voltage, Synchronous Buck Controllers Featuring Adaptive On-Time Control |
| MIC2176-2YMM | 功能描述:DC/DC 开关控制器 76V Synchronous Buck Controller RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
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