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| 型号： | MAX5974DETE+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 15/27页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR FLYBACK PWM 16-TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 1 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 600kHz |
| 占空比： | 82% |
| 电源电压： | 12 V ~ 24 V |
| 降压： | 无 |
| 升压： | 无 |
| 回扫： | 是 |
| 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： | 16-WFQFN 裸露焊盘 |
| 包装： | 管件 |
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MAX5974A/MAX5974B/MAX5974C/MAX5974D
Active-Clamped, Spread-Spectrum,
Current-Mode PWM Controllers
Detailed Description
The MAX5974A/MAX5974B/MAX5974C/MAX5974D are
optimized for controlling a 25W to 50W active-clamped,
self-driven synchronous rectification forward converter
in continuous-conduction mode. The main switch gate
driver (NDRV) and the active-clamped switch driver
(AUXDRV) are sized to optimize efficiency for 25W
design. The features-rich devices are ideal for PoE IEEE
802.3af/at-powered devices.
The MAX5974A/MAX5974C offer a 16V bootstrap UVLO
wake-up level with a 9V wide hysteresis. The low startup
and operating currents allow the use of a smaller storage
capacitor at the input without compromising startup and
hold times. The MAX5974A/MAX5974C are well-suited
for universal input (rectified 85V AC to 265V AC) or tele-
com (-36V DC to -72V DC) power supplies.
The MAX5974B/MAX5974D have a UVLO rising threshold
of 8.4V and can accommodate for low-input voltage (12V
DC to 24V DC) power sources such as wall adapters.
Power supplies designed with the MAX5974A/MAX5974C
use a high-value startup resistor, R IN , that charges a
reservoir capacitor, C IN (see the Typical Application
Circuits ). During this initial period, while the voltage is
less than the internal bootstrap UVLO threshold, the
device typically consumes only 100 F A of quiescent cur-
rent. This low startup current and the large bootstrap
UVLO hysteresis help to minimize the power dissipation
across R IN even at the high end of the universal AC input
voltage (265V AC).
Feed-forward maximum duty-cycle clamping detects chang-
es in line conditions and adjusts the maximum duty cycle
accordingly to eliminate the clamp voltage’s (i.e., the main
power FET’s drain voltage) dependence on the input voltage.
For EMI-sensitive applications, the programmable fre-
quency dithering feature allows up to Q 10% variation in
the switching frequency. This spread-spectrum modula-
tion technique spreads the energy of switching harmon-
ics over a wider band while reducing their peaks, help-
ing to meet stringent EMI goals.
Maxim Integrated
The devices include a cycle-by-cycle current limit
that turns off the main and AUX drivers whenever the
internally set threshold of 400mV is exceeded. Eight
consecutive occurrences of current-limit events trigger
hiccup mode, which protects external components by
halting switching for a period of time (t RSTRT ) and allow-
ing the overload current to dissipate in the load and
body diode of the synchronous rectifier before soft-start
is reattempted.
The reverse current-limit feature of the devices turns
the AUX driver off for the remaining off period when
V CS exceeds the -100mV threshold. This protects the
transformer core from saturation due to excess reverse
current under some extreme transient conditions.
Current-Mode Control Loop
The advantages of current-mode control over voltage-
mode control are twofold. First, there is the feed-forward
characteristic brought on by the controller’s ability to adjust
for variations in the input voltage on a cycle-by-cycle basis.
Second, the stability requirements of the current-mode
controller are reduced to that of a single-pole system,
unlike the double pole in voltage-mode control.
The devices use a current-mode control loop where the
scaled output of the error amplifier (COMP) is compared
to a slope-compensated current-sense signal at CSSC.
Input Clamp
When the device is enabled, an internal 18V input clamp
is active. During an overvoltage condition, the clamp
prevents the voltage at the supply input IN from rising
above 18.5V (typ).
When the device is disabled, the input clamp circuitry is
also disabled.
Enable Input
The enable input is used to enable or disable the device.
Driving EN low disables the device. Note that the inter-
nal 18V input clamp is also disabled when EN is low.
Therefore, an external 18V zener diode is needed for
certain operating conditions as described below.
15
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX5974DETE+ | 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 |
| MAX5974DETE+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 |
| MAX5974EETE+ | 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 |
| MAX5974EETE+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 |
| MAX5974EEVKIT# | 功能描述:电流型 PWM 控制器 MAX5974E Eval Kit 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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