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| 型号： | MIC2124YMM |
| 厂商： | Micrel Inc |
| 文件页数： | 10/24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.
MIC2124
until V LX > -127mV, and then goes into the ON status
with minimum ON-time. The current limit threshold V CL
has a fold back characteristic related to the FB voltage.
Please refer to the “Typical Characteristics” for the curve
of V CL vs. FB voltage. The circuit in Figure 4 illustrates
the MIC2124 current limiting circuit.
Figure 3. MIC2124 Load-Transient Response
Figure 4. MIC2124 Current Limiting Circuit
Unlike in current-mode control, the MIC2124 uses
I CL ≈
127mV Δ I L(pp)
I CL(LOAD) =
Δ I L(pp) =
V OUT × (1 ? D)
adaptive ON-time current mode control. The MIC2124
predetermined ON-time control loop has the advantage
of constant ON-time mode control and eliminates the
need for the slope compensation.
Soft-Start
Soft-start reduces the power supply input surge current
at startup by controlling the output voltage rise time. The
input surge appears while the output capacitor is
charged up. A slower output rise time will draw a lower
input surge current.
The MIC2124 implements an internal digital soft-start by
making the 0.8V reference voltage V REF ramp from 0 to
100% in about 4ms. Therefore, the output voltage is
controlled to increase slowly by a stair-case V REF ramp.
Once the soft-start cycle ends, the related circuitry is
disabled to reduce current consumption. V IN must be
powered up no earlier than V HSD to make the soft-start
function behavior correctly.
Current Limit
The MIC2174/MIC2174C uses the RSD(ON) of the low-
side power MOSFET to sense over-current conditions.
This method will avoid adding cost, board space and
power losses taken by a discrete current sense resistor.
The low-side MOSFET is used because it displays much
lower parasitic oscillations during switching than the
high-side MOSFET.
In each switching cycle of the MIC2124 converter, the
inductor current is sensed by monitoring the low-side
MOSFET in the OFF period. The sensed voltage V LX is
compared with a current-limit threshold voltage V CL after
a blanking time of 150ns. If the sensed voltage V LX is
under V CL , which is -127mV typical at 0.8V feedback
voltage, the MIC2124 keeps the low-side MOSFET on
Using the typical V CL value of -127mV, the current limit
value in the inductor is roughly estimated as:
127mV
R DS(ON)
For designs where the inductor current ripple is
significant compared to the load current I OUT , or for low
duty cycle operation, calculating the load current limit
I CL(LOAD) should take into account that one is sensing the
peak inductor current.
? (2)
R DS(ON) 2
(3)
f SW × L
where:
V OUT = The output voltage
Δ I L(pp) = Inductor current ripple peak-to-peak value
D = Duty Cycle
f SW = Switching frequency
The MOSFET R DS(ON) varies 30% to 40% with
temperature; therefore, it is recommended to add 50%
margin to I CL(LOAD) in the above equation to avoid false
current limiting due to increased MOSFET junction
temperature rise. It is also recommended to connect LX
pin directly to the drain of the low-side MOSFET to
accurately sense the MOSFETs R DS(ON)
June 2010
10
M9999-060810-D
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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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