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参数资料
| 型号： | MIC28500 2A EV |
| 厂商： | Micrel Inc |
| 文件页数： | 14/29页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL FOR MIC28500 2A |
| 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： | 12V |
| 电流 - 输出： | 2A |
| 输入电压： | 30 ~ 75V |
| 稳压器拓扑结构： | 降压 |
| 频率 - 开关： | 250kHz |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | MIC28500 |
| 其它名称： | 576-4019 |
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Micrel, Inc.
Functional Description
The MIC28500 is an adaptive ON-time synchronous
step-down DC-DC regulator. It is designed to operate
over a wide input voltage range from, 30V to 75V, and
provides a regulated output voltage at up to 4A of output
current. 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 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
Figure 1 illustrates the block diagram for the control loop
of the MIC28500. The output voltage is sensed by the
MIC28500 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 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:
MIC28500
where t S = 1/f SW . It is not recommended to use
MIC28500 with a OFF-time close to t OFF(min) during
steady-state operation..
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 75V to 1.0V. The minimum t ON
measured on the MIC28500 evaluation board is about
184ns. During load transients, the switching frequency is
changed due to the varying OFF-time.
Figure 2 shows the MIC28500 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.
t ON(estimat ed) =
V OUT
V IN × f SW
Eq. 1
where V OUT is the output voltage and V IN is the power
stage input voltage and f SW is the switching frequency.
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, then the MIC28500 control logic will apply the
t OFF(min) instead. The minimum t OFF(min) period 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 360ns t OFF(min) :
Figure 2. MIC28500 Control Loop Timing
D max =
June 2011
t S ? t OFF(min)
t S
= 1 ?
360ns
t S
Eq. 2
14
M9999-060311-B
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相关代理商/技术参数 |
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|---|---|
| MIC28500YJL TR | 功能描述:直流/直流开关调节器 75V/4A DC-DC Buck Regulator with HSC 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 |
| MIC28500YJLTR | 制造商:Micrel 功能描述:Conv DC DC Step Down 0.8 12V 28 Pin MLF |
| MIC28500YJL-TR | 功能描述:Buck Switching Regulator IC Positive Adjustable 0.8V 1 Output 4A 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:过期 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）:30V 电压 - 输入（最大值）:75V 电压 - 输出（最小值/固定）:0.8V 电压 - 输出（最大值）:61.5V 电流 - 输出:4A 频率 - 开关:100kHz ~ 500kHz 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 |
| MIC28510 12V EV | 功能描述:电源管理IC开发工具 75V/4A DC-DC Buck Regulator with HSC - 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 |
| MIC28510 5V EV | 功能描述:电源管理IC开发工具 75V/4A DC-DC Buck Regulator with HSC - 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 |
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