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| 型号： | MIC2124YMM |
| 厂商： | Micrel Inc |
| 文件页数： | 9/24页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 10-MSOP |
| 产品培训模块： | MIC2124 Synchronous Current Mode DC-DC Buck Controller |
| 标准包装： | 100 |
| 系列： | Hyper Speed Control™ |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 360kHz |
| 占空比： | 93% |
| 电源电压： | 3 V ~ 5.5 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） |
| 包装： | 管件 |
| 其它名称： | 576-3639-5 MIC2124YMM-ND |
Micrel, Inc.
Functional Description
The MIC2124 is an adaptive on-time current mode
synchronous buck controller built for low cost and high
performance. It is designed for wide input voltage range
from 3V to 18V and for high output power buck
converters. An estimated-ON-time method is applied in
MIC2124 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 MIC2124 is an adaptive on-time current mode buck
controller. Figure 1 illustrates the block diagram for the
control loop. The output voltage variation due to load or
line changes will be sensed by the inverting input of the
transconductance error amplifier via the feedback
resistors (R FB1 and R FB2 in “Typical Application”), and
compared to a reference voltage at the non-inverting
input. This will cause a small change in the DC voltage
level at the output of the error amplifier, or V COMP .
Meanwhile, the inductor current is sensed through the
bottom MOSFET R DS(ON) and “Bottom Current Sense
Circuit” as V IL . If V IL is lower than V COMP , an ON-time
period is triggered, in which DH pin is logic high and DL
pin is logic low. The ON-time period length is
predetermined by the “Fixed Ton Estimator” circuitry:
MIC2124
300kHz switching frequency. The actual ON-time varies
a little with the different rising and falling times of the
external MOSFETs. Therefore, the type of the external
MOSFETs, the output load current, and the control
circuitry power supply V IN will slightly modify the actual
ON-time and the switching frequency. Also, the minimum
T ON , which is 140ns typical, results in a lower switching
frequency in high V HSD and low V OUT applications, such
as 18V to 0.8V. 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. V COMP is
defined as the output of the error amplifier. Figure 2
shows the MIC2124 control loop timing during the
steady-state operation in continuous mode. V IL
represents the inductor current sensing voltage via the
bottom MOSFET R DS(ON) and “Bottom Current Sense
Circuit”. When V IL is below V COMP , which means that the
inductor current reaches the valley value, the OFF-time
ends and ON-time is triggered. The ON-time is
predetermined by the estimation.
T ON(estimat ed) =
V OUT
V HSD ? 300kHz
(1)
D MAX =
T S ? T OFF(min) 350ns
where V OUT is the output voltage, V HSD is the power
stage input voltage.
After an ON-time period, the MIC2124 goes into the
OFF-time period, in which DH pin is logic low and DL pin
is logic high. The inductor current and V IL decrease
during OFF time. If V IL is above V COMP , the OFF status is
maintained. When V IL is below V COMP , the ON-time
period is triggered and the OFF-time period ends. If the
OFF-time period determined by the inductor current and
V COMP is less than the minimum OFF time T OFF(min) , which
is 350ns typical, the MIC2124 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. The maximum duty cycle is obtained
from the 350ns T OFF(min) :
= 1 ?
T S T S
where T S = 1/300kHz = 3.33 μ s. It is not recommended to
use MIC2124 with a OFF-time close to T OFF(min) during
steady state operation.
Figure 2. MIC2124 Control Loop Timing
Figure 3 shows the load transient operation of the
MIC2124 converter. Assume the output voltage drops
due to sudden load increase, which would cause the
inverting input of the error amplifier, which is divided
down version of V OUT , to be slightly less than the
reference voltage, causing the output voltage of the error
amplifier V COMP to go high. This will cause “CONTROL
LOGIC” to trigger ON-time period. At the end of the ON-
time period, a minimum OFF-time T OFF(min) is generated
to charge BST since the inductor current V IL is still below
V COMP . Then, the next ON-time period is triggered due to
the high V COMP . Therefore, the switching frequency
changes during the load transient. Also the load
regulation and transient load recovery is done by
modulating the OFF-time. With the varying duty cycle
and switching frequency, the output recovery time is fast
and the output voltage deviation is small in MIC2124
converter.
The estimated ON-time method results in a constant
June 2010
9
M9999-060810-D
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相关代理商/技术参数 |
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| MIC2124YMM TR | 功能描述:DC/DC 开关控制器 Synch Buck Controller with Adaptive On-Time Control 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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| MIC2130-1YML | 制造商:Rochester Electronics LLC 功能描述: 制造商:RF Micro Devices Inc 功能描述: |
| MIC2130-1YML TR | 功能描述:DC/DC 开关控制器 High Voltage Synchronous Buck Control IC 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 |
| MIC2130-1YML-TR | 功能描述:Buck Regulator Positive Output Step-Down DC-DC Controller IC 16-MLF? (4x4) 制造商:microchip technology 系列:- 包装:剪切带（CT） 零件状态:停产 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:1 输出阶段:1 电压 - 电源（Vcc/Vdd）:8 V ~ 40 V 频率 - 开关:150kHz 占空比（最大）:0.92 同步整流器:是 时钟同步:无 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:16-VQFN 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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