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| 型号： | MAX5974AEVKIT# |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 19/27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
Peak Current Limit
The current-sense resistor (R CS in the Typical
Application Circuits ), connected between the source
of the n-channel MOSFET and PGND, sets the current
limit. The current-limit comparator has a voltage trip level
(V CS-PEAK ) of 400mV. Use the following equation to cal-
culate the value of R CS :
400mV. The duty cycle is terminated immediately when
V CS exceeds 400mV.
Reverse Current Limit
The devices protect the transformer against saturation
due to reverse current by monitoring the voltage across
R CS while the AUX output is low and the p-channel FET
is on.
R CS =
400mV
I PRI
Output Short-Circuit Protection
with Hiccup Mode
When the device detects eight consecutive peak current-
where I PRI is the peak current in the primary side of
the transformer, which also flows through the MOSFET.
When the voltage produced by this current (through the
current-sense resistor) exceeds the current-limit com-
parator threshold, the MOSFET driver (NDRV) terminates
the current on-cycle, within 35ns (typ).
The devices implement 115ns of leading-edge blanking
to ignore leading-edge current spikes. These spikes
are caused by reflected secondary currents, current-
discharging capacitance at the FET’s drain, and gate-
charging current. Use a small RC network for additional
filtering of the leading-edge spike on the sense wave-
form when needed. Set the corner frequency between
10MHz and 20MHz.
After the leading-edge blanking time, the device moni-
tors V CS for any breaches of the peak current limit of
V CSBL
(BLANKED CS
limit events, both NDRV and AUXDRV driver outputs are
turned off for a restart period, t RSTRT . After t RSTRT , the
device undergoes soft-start. The duration of the restart
period depends on the value of the capacitor at SS (C SS ).
During this period, C SS is discharged with a pulldown cur-
rent of I SS-DH (2 F A typ). Once its voltage reaches 0.15V,
the restart period ends and the device initiates a soft-start
sequence. An internal counter ensures that the minimum
restart period (t RSTRT-MIN ) is 1024 clock cycles when the
time required for C SS to discharge to 0.15V is less than
1024 clock cycles. Figure 6 shows the behavior of the
device prior and during hiccup mode.
Frequency Foldback for High-Efficiency
Light-Load Operation
The frequency foldback threshold can be programmed
from 0 to 20% of the full load current using a resistor from
FFB to GND.
V CS-PEAK
(400mV)
VOLTAGE)
HICCUP
DISCHARGE WITH I SS-DH
V SS-HI
SOFT-START
VOLTAGE,
V SS
t SS
t RSTRT
V SS-DTH
Figure 6. Hiccup Mode Timing Diagram
Maxim Integrated
19
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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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