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参数资料
| 型号： | MIC2176-1YMM TR |
| 厂商： | Micrel Inc |
| 文件页数： | 14/31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： | 125kHz |
| 占空比： | 96% |
| 电源电压： | 4.5 V ~ 75 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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t S ? t OFF(min) 360ns
t ON(estimat ed) =
V OUT
Micrel, Inc.
Functional Description
The MIC2176 is an adaptive on-time synchronous buck
controller family built for high-input voltage and low
output voltage applications. It is designed to operate
over a wide input voltage range from, 4.5V to 75V and
the output is adjustable with an external resistive divider.
A digitally modified adaptive on-time control scheme is
employed in to obtain a constant switching frequency
and to simplify the control compensation. Over-current
protection is implemented by sensing low-side
MOSFET’s R DS(ON) . The device features internal soft-
start, enable, UVLO, and thermal shutdown.
Theory of Operation
Figure 1 illustrates the block diagram of the MIC2176.
The output voltage is sensed by the MIC2176 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 (g m ) amplifier. If
the feedback voltage decreases and the amplifier output
is below 0.8V, then the error comparator will trigger the
control logic and generate an ON-time period. The ON-
time period length is predetermined by the “Fixed t ON
Estimator” circuitry:
(1)
V IN × f SW
where V OUT is the output voltage, V IN is the power stage
input voltage, and f SW is the switching frequency
(100kHz for MIC2176-1, 200kHz for MIC2176-2, and
300kHz for MIC2176-3).
MIC2176
The maximum duty cycle is obtained from the 360ns
t OFF(min) :
D max = = 1 ? (2)
t S t S
where t S = 1/f SW . It is not recommended to use MIC2176
with a OFF-time close to t OFF(min) during steady-state
operation.
The adpative ON-time control scheme results in a
constant switching frequency in the MIC2176. The actual
ON-time and resulting switching frequency will vary with
the different rising and falling times of the external
MOSFETs. Also, the minimum t ON results in a lower
switching frequency in high V IN to V OUT applications,
such as 48V to 1.0V. The minimum t ON measured on the
MIC2176 evaluation board is about 60ns. During load
transients, the switching frequency is changed due to the
varying OFF-time.
To illustrate the control loop operation, we will analyze
both the steady-state and load transient scenarios. For
easy analysis, the gain of the g m amplifier is assumed to
be 1. With this assumption, the inverting input of the
error comparator is the same as the feedback voltage.
Figure 2 shows the MIC2176 control loop timing during
steady-state operation. During steady-state, the g m
amplifier senses the feedback voltage ripple, which is
proportional to the output voltage ripple plus injected
voltage ripple, to trigger the ON-time period. The ON-
time is predetermined by the t ON estimator. The
termination of the OFF-time is controlled by the feedback
voltage. At the valley of the feedback voltage ripple,
which occurs when V FB falls below V REF , the OFF period
ends and the next ON-time period is triggered through
the control logic circuitry.
At the end of the ON-time period, the internal high-side
driver turns off the high-side MOSFET and the low-side
driver turns on the low-side MOSFET. The OFF-time
period length depends upon the feedback voltage in
most cases. When the feedback voltage decreases and
the output of the g m amplifier is below 0.8V, the ON-time
period is triggered and the OFF-time period ends. If the
OFF-time period determined by the feedback voltage is
less than the minimum OFF-time t OFF(min) , which is about
360ns, the MIC2176 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.
Figure 2. MIC2176 Control Loop Timing
November 2010
14
M9999-111710-A
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 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 |
| MIC2176-2YMM 5A EV | 功能描述:电源管理IC开发工具 76V Synchronous Buck Controller - Evaluation Board RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| MIC2176-2YMM 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 |
| MIC2176-3 | 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 |
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