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参数资料
| 型号： | MAX1957EUB+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 15/22页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 10-UMAX |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 50 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 360kHz |
| 占空比： | 96% |
| 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 |
Low-Cost, High-Frequency, Current-Mode PWM
Buck Controller
Design Procedures
Setting the Output Voltage
R 1 = R 2 × ? OUT ? 1 ?
IN
MAX1953
MAX1954
MAX1957
Figure 5. DH Boost Circuit
BST
DH
LX
DL
To set the output voltage for the MAX1953/MAX1954,
connect FB to the center of an external resistor-divider
connected between the output to GND (Figures 1 and
2). Select R2 between 8k ? and 24k ? , and then calcu-
late R1 by:
? V ?
? V FB ?
where V FB = 0.8V. R1 and R2 should be placed as
close to the IC as possible.
For the MAX1957, connect FB directly to the output
through a decoupling resistor of 10k ? to 21k ? (Figure
3). The output voltage is then equal to the voltage at
( )
( )
Once these conditions are met, the step-down controller
enables soft-start and starts switching. The soft-start cir-
cuitry gradually ramps up to the feedback-regulation
voltage in order to control the rate-of-rise of the output
voltage and reduce input surge currents during startup.
The soft-start period is 1024 clock cycles (1024/f S ,
MAX1954/MAX1957) or 4096 clock cycles (4096/f S ,
MAX1953) and the internal soft-start DAC ramps the
voltage up in 64 steps. The output reaches regulation
when soft-start is completed, regardless of output
capacitance and load.
Shutdown
The MAX1953/MAX1954/MAX1957 feature a low-power
shutdown mode. Use an open-collector transistor to
pull COMP low to shut down the IC. During shutdown,
the output is high impedance. Shutdown reduces the
quiescent current (I Q ) to approximately 220μA.
Thermal Overload Protection
Thermal overload protection limits total power dissipation
in the MAX1953/MAX1954/MAX1957. When the junction
temperature exceeds T J = +160°C, an internal thermal
sensor shuts down the device, allowing the IC to cool.
The thermal sensor turns the IC on again after the junc-
tion temperature cools by 15°C, resulting in a pulsed out-
put during continuous thermal overload conditions.
REFIN. Again, this resistor should be placed as close to
the IC as possible.
Determining the Inductor Value
There are several parameters that must be examined
when determining which inductor is to be used. Input
voltage, output voltage, load current, switching frequen-
cy, and LIR. LIR is the ratio of inductor current ripple to
DC load current. A higher LIR value allows for a smaller
inductor, but results in higher losses and higher output
ripple. A good compromise between size, efficiency,
and cost is an LIR of 30%. Once all of the parameters
are chosen, the inductor value is determined as follows:
V OUT × V IN ? V OUT
L =
V IN × f S × I LOAD MAX × LIR
where f S is the switching frequency. Choose a standard
value close to the calculated value. The exact inductor
value is not critical and can be adjusted in order to
make trade-offs among size, cost, and efficiency. Lower
inductor values minimize size and cost, but they also
increase the output ripple and reduce the efficiency due
to higher peak currents. By contrast, higher inductor val-
ues increase efficiency, but eventually resistive losses
due to extra turns of wire exceed the benefit gained
from lower AC current levels.
For any area-restricted applications, find a low-core
loss inductor having the lowest possible DC resistance.
Ferrite cores are often the best choice, although pow-
dered iron is inexpensive and can work well at 300kHz.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1957EUB+ | 功能描述:电流型 PWM 控制器 High-f Current-Mode PWM Buck Controller RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1957EUB+T | 功能描述:电流型 PWM 控制器 High-f Current-Mode PWM Buck Controller RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1957EUB-T | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX19586ETN | 功能描述:模数转换器 - ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| MAX19586ETN+D | 功能描述:模数转换器 - ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
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