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| 型号： | MAX8742EAI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 20/34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
voltage. A linear postregulator may still be needed to
meet strict output-accuracy specifications.
The MAX8742 has a V DD pin that regulates at a fixed
13.5V, set by an internal resistor-divider. The MAX8741
has an adjustable secondary-output voltage set by an
external resistor-divider on SECFB (Figure 5). Ordinarily,
the secondary regulation point is set 5% to 10% below
the voltage normally produced by the flyback effect. For
example, if the output voltage as determined by turns
ratio is 15V, set the feedback resistor ratio to produce
13.5V. Otherwise, the SECFB one-shot might be triggered
unintentionally, unnecessarily increasing supply current
and output noise.
12V Linear-Regulator Output (MAX8742)
The MAX8742 includes a 12V linear-regulator output
capable of delivering 120mA of output current.
Typically, greater current is available at the expense of
output accuracy. If an accurate output of more than
120mA is needed, an external pass transistor can be
added. The circuit in Figure 6 delivers more than
200mA. Total output current is constrained by the V+
input voltage and the transformer primary load (see the
Maximum V DD Output Current vs. Input Voltage graphs
in the Typical Operating Characteristics ).
Design Procedure
The three predesigned 3V/5V standard application cir-
cuits (Figure 1 and Table 1) contain ready-to-use solu-
tions for common application needs. Also, one
standard flyback transformer circuit supports the
12OUT linear regulator in the Applications Information
section. Use the following design procedure to optimize
these basic schematics for different voltage or current
requirements. Before beginning a design, however,
firmly establish the following:
? Maximum Input (Battery) Voltage, V IN(MAX) . This
value should include the worst-case conditions,
such as no-load operation when a battery charger or
AC adapter is connected but no battery is installed.
V IN(MAX) must not exceed 30V.
? Minimum Input (Battery) Voltage, V IN(MIN) .This
should be taken at full load under the lowest battery
conditions. If V IN(MIN) is less than 4.2V, use an exter-
nal circuit to externally hold V L above the V L undervolt-
age- lockout threshold. If the minimum input-output
difference is less than 1.5V, the filter capacitance
required to maintain good AC load regulation increas-
es (see the Low-Voltage Operation section).
SECFB
R2
12OUT
0.1 μ F
12V OUTPUT
200mA
10 μ F
1-SHOT
TRIG
2.5V REF
V+
R1
POSITIVE
SECONDARY
V DD
0.1 μ F
10 Ω
2N3906
OUTPUT
DH_
MAX8742
V+
0.1 μ F
V DD OUTPUT
MAX8741
MAIN
OUTPUT
DH_
2.2 μ F
DL_
MAIN
OUTPUT
(
)
R1
+V TRIP = V REF 1 + –––
R2
WHERE V REF (NOMINAL) = 2.5V
DL_
Figure 5. Adjusting the Secondary Output Voltage with SECFB
Figure 6. Increased 12V Linear-Regulator Output Current
20
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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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