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参数资料
| 型号： | MAX5974AEVKIT# |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 17/27页 |
| 文件大小： | 0K |
| 描述： | EVAL KIT MAX5974A |
| 标准包装： | 1 |
| 系列： | * |
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MAX5974A/MAX5974B/MAX5974C/MAX5974D
Active-Clamped, Spread-Spectrum,
Current-Mode PWM Controllers
V S
Because the MAX5974B/MAX5974D are designed for
use with low-voltage power sources such as wall adapt-
ers outputting 12V to 24V, they have a lower UVLO
wake-up threshold of 8.4V.
R IN
C IN
DIGITAL
CONTROL
R EN
IN
EN
MAX5974
Startup Operation
The device starts up when the voltage at IN exceeds 16V
(MAX5974A/MAX5974C) or 8.4V (MAX5974B/MAX5974D)
and the enable input voltage is greater than 1.26V.
During normal operation, the voltage at IN is nor-
mally derived from a tertiary winding of the transformer
(MAX5974C/MAX5974D). However, at startup there is
no energy being delivered through the transformer;
hence, a special bootstrap sequence is required. In the
N
Figure 3. High-Voltage Logic Control of the Enable Input
Typical Application Circuits , C IN charges through the
startup resistor, R IN , to an intermediate voltage. Only
100 F A of the current supplied through R IN is used by
the ICs, the remaining input current charges C IN until
V IN reaches the bootstrap UVLO wake-up level. Once
V IN exceeds this level, NDRV begins switching the
n-channel MOSFET and transfers energy to the second-
ary and tertiary outputs. If the voltage on the tertiary
output builds to higher than 7V (the bootstrap UVLO
R IN
V S
IN
shutdown level), then startup has been accomplished
and sustained operation commences. If V IN drops below
7V before startup is complete, the device goes back to
low-current UVLO. In this case, increase the value of C IN
in order to store enough energy to allow for the voltage
at the tertiary winding to build up.
C IN
Figure 4. Always-On Operation
EN
MAX5974_
Always-On Operation
While the MAX5974A/MAX5974B derive their input volt-
age from the coupled inductor output during normal
operation, the startup behavior is similar to that of the
MAX5974C/MAX5974D.
Soft-Start
A capacitor from SS to GND, C SS , programs the soft-
start time. V SS controls the oscillator duty cycle during
startup to provide a slow and smooth increase of the
duty cycle to its steady-state value. Calculate the value
of C SS as follows:
For always-on operation, connect EN to IN as shown
C SS = SS-CH SS
in Figure 4. No external zener diode is needed for this
configuration.
Bootstrap Undervoltage Lockout
The devices have an internal bootstrap UVLO that is very
useful when designing high-voltage power supplies (see
the Block Diagrams ). This allows the device to bootstrap
itself during initial power-up. The MAX5974A/MAX5974C
soft-start when V IN exceeds the bootstrap UVLO thresh-
old of V INUVR (16V typ).
Maxim Integrated
I × t
2V
where I SS-CH (10 F A typ) is the current charging C SS dur-
ing soft-start and t SS is the programmed soft-start time.
A resistor can also be added from the SS pin to GND to
clamp V SS < 2V and, hence, program the maximum duty
cycle to be less than 80% (see the Duty-Cycle Clamping
section).
17
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX5974AEVKIT# | 功能描述:电源管理IC开发工具 MAX5974A Eval Kit 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 |
| MAX5974BETE+ | 功能描述:电流型 PWM 控制器 Current-Mode PWM 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 |
| MAX5974BETE+T | 功能描述:电流型 PWM 控制器 Current-Mode PWM 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 |
| MAX5974CETE+ | 功能描述:电流型 PWM 控制器 Current-Mode PWM 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 |
| MAX5974CETE+T | 功能描述:电流型 PWM 控制器 Current-Mode PWM 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 |
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