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| 型号： | MIC261201YJL EV |
| 厂商： | Micrel Inc |
| 文件页数： | 15/30页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL FOR MIC261201YJL |
| 标准包装： | 1 |
| 系列： | Hyper Speed Control™，SuperSwitcher II™ |
| 主要目的： | DC/DC，步降 |
| 输出及类型： | 1，非隔离 |
| 输出电压： | 5V |
| 电流 - 输出： | 12A |
| 输入电压： | 5.5 ~ 28 V |
| 稳压器拓扑结构： | 降压 |
| 频率 - 开关： | 600kHz |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | MIC261201 |
| 其它名称： | 576-4013 |
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Micrel, Inc.
Functional Description
The MIC261201 is an adaptive ON-time synchronous
MIC261201
The maximum duty cycle is obtained from the 300ns
t OFF(min) :
step-down DC/DC regulator with an internal 5V linear
regulator and a Power Good (PG) output. It is designed
to operate over a wide input voltage range from 4.5V to
28V and provides a regulated output voltage at up to 7A
D max =
t S - t OFF(min)
t S
= 1 -
300ns
t S
Eq. 2
of output current. An adaptive ON-time control scheme is
t ON(estimat ed) =
V OUT
employed to obtain a constant switching frequency and
to simplify the control compensation. Over-current
protection is implemented without the use of an external
sense resistor. The device 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 MIC261201 operates in a continuous mode as
shown in Figure 1.
Continuous Mode
In continuous mode, the output voltage is sensed by the
MIC261201 feedback (FB) pin 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 output of the g m amplifier 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
ESTIMATION” circuitry:
Eq. 1
V IN × 600kHz
where V OUT is the output voltage and V IN is the power
stage input voltage.
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
300ns, the MIC261201 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.
where t S = 1/600kHz = 1.66 μ s.
It is not recommended to use MIC261201 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
MIC261201 should be limited to 5.5V and the maximum
external ripple injection should be limited to 200mV.
Please refer to “Setting Output Voltage” subsection in
Application Information for more details.
The actual ON-time and resulting switching frequency
will vary with the part-to-part variation in the rise and fall
times of the internal MOSFETs, the output load current,
and variations in the V DD voltage. Also, the minimum t ON
results in a lower switching frequency in high V IN to V OUT
applications, such as 24V to 1.0V. The minimum t ON
measured on the MIC261201 evaluation board is about
100ns. 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.
Figure 2 shows the MIC261201 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 and the inductor
current 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.
July 2011
15
M9999-071311-A
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| MIC261201YJL-TR | 功能描述:Buck Switching Regulator IC Positive Adjustable 0.8V 1 Output 12A 28-PowerVQFN Variant, 28-MLF? 制造商:microchip technology 系列:Hyper Speed Control?，SuperSwitcher II? 包装:剪切带（CT） 零件状态:有效 功能:降压 输出配置:正 拓扑:降压 输出类型:可调式 输出数:1 电压 - 输入（最小值）:4.5V 电压 - 输入（最大值）:28V 电压 - 输出（最小值/固定）:0.8V 电压 - 输出（最大值）:5.5V 电流 - 输出:12A 频率 - 开关:600kHz 同步整流器:是 工作温度:-40°C ~ 125°C （TJ） 安装类型:表面贴装 封装/外壳:28-PowerVQFN 变式，28-MLF? 供应商器件封装:28-MLF?（5x6） 标准包装:1 |
| MIC261201YML | 制造商:Micrel 功能描述:DC-DC Buck Regulator 28V 12A Adj MLF28 |
| MIC261203YJL EV | 功能描述:电源管理IC开发工具 28V/12A DC-DC Buck Regulator w/ HLL - 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 |
| MIC261203YJL TR | 功能描述:直流/直流开关调节器 28V/12A DC-DC Buck Regulator w/ HLL RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MIC261203YJLEV | 制造商:Micrel Inc 功能描述:Evaluation Board for MIC261203YJL |
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