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| 型号： | MAX8742EAI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 26/34页 |
| 文件大小： | 0K |
| 描述： | IC CNTRLR PWR SUP 28-SSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,000 |
| 应用： | 控制器，笔记本电脑电源系统 |
| 输入电压： | 4.2 V ~ 30 V |
| 输出数： | 2 |
| 输出电压： | 3.3V，5V，2.5 V ~ 5.5 V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-SSOP（0.209"，5.30mm 宽） |
| 供应商设备封装： | 28-SSOP |
| 包装： | 带卷 (TR) |
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500kHz Multi-Output Power-Supply Controllers
with High Impedance in Shutdown
scale down the voltage. Use the maximum inductance
and minimum DCR to get the maximum possible induc-
tor time constant. Select R S and C S so that the maxi-
mum sense-network time constant is equal to or greater
than the maximum inductor time constant.
Reduced Output-Capacitance Application
In applications where higher output ripple is accept-
able, lower output capacitance or higher ESR output
capacitors can be used. In such cases, cycle-by-cycle
stability is maintained by adding feed-forward compen-
sation to offset for the increased output ESR. Figure 8
shows the addition of the feed-forward compensation
circuit. C FB provides noise filtering, R FF is the feed-for-
ward resistor, and C LX provides DC blocking. Use
100pF for C FB and C LX . Select R FF according to the
equation below:
The PC board layout artist must be given explicit
instructions, preferably a pencil sketch showing the
placement of power-switching components and high-
current routing. A ground plane is essential for optimum
performance. In most applications, the circuit is located
on a multilayer board, and full use of the four or more
copper layers is recommended. Use the top layer for
high-current connections, the bottom layer for quiet
connections (REF, SS, GND), and the inner layers for
an uninterrupted ground plane. Use the following step-
by-step guide:
1) Place the high-power components (Figure 1, C1, C3,
C4, Q1, Q2, L1, and R1) first, with their grounds
adjacent:
? Priority 1: Minimize current-sense resistor trace
lengths and ensure accurate current sensing with
Kelvin connections (Figure 9).
R FF ≤
4 × R3 × L × f
ESR
? Priority 2: Minimize ground trace lengths in the
high-current paths (discussed below).
? Priority 3: Minimize other trace lengths in the
Set the value for R FF close to the calculation. Do not
make R FF too small as that introduces too much feed-
forward, possibly causing an overvoltage to be seen at
the feedback pin, and changing the mode of operation
to a voltage mode.
PC Board Layout Considerations
Good PC board layout is required in order to achieve
specified noise, efficiency, and stability performance.
V IN
high-current paths.
a) Use >5mm-wide traces
b) CIN to high-side MOSFET drain: 10mm max
length
c) Rectifier diode cathode to low-side MOSFET:
5mm max length
DH_
C IN
V IN
INDUCTOR
DH_
C IN
LX_
R S
L
R L
C S
V OUT
CSL_
CSH_
LX_
L
R SENSE
V OUT
MAX8741
MAX8742
CSH_
CSL_
C OUT
MAX8741
MAX8742
FB_
C LX
R FF
C FB
R3
C OUT
DL_
DL_
R4
Figure 7. Lossless Inductor Current Sensing
Figure 8. Adding Feed-Forward Compensation
26
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8743EEI | 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 |
| MAX8743EEI+ | 功能描述:电流型 PWM 控制器 Dual Step-Down 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 |
| MAX8743EEI+T | 功能描述:电流型 PWM 控制器 Dual Step-Down 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 |
| MAX8743EEI-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 |
| MAX8743ETX | 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 |
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