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参数资料
| 型号： | MAX5974AEVKIT# |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 21/27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
Programmable Slope Compensation
The device generates a current ramp at CSSC such that
its peak is 50 F A at 80% duty cycle of the oscillator. An
external resistor connected from CSSC to the CS then
converts this current ramp into programmable slope-
compensation amplitude, which is added to the current-
sense signal for stability of the peak current-mode
control loop. The ramp rate of the slope compensation
signal is given by:
Applications Information
Startup Time Considerations
The bypass capacitor at IN, C IN , supplies current
immediately after the devices wake up (see the Typical
Application Circuits ). Large values of C IN increase
the startup time, but also supply gate charge for more
cycles during initial startup. If the value of C IN is too
small, V IN drops below 7V because NDRV does not have
enough time to switch and build up sufficient voltage
m =
R CSSC × 50 μ A × f SW
80%
across the tertiary output (MAX5974C/MAX5974D) or
coupled inductor output (MAX5974A/MAX5974B), which
powers the device. The device goes back into UVLO
= V REF × FB1 FB2
V OUT
C IN = IN G SS
where m is the ramp rate of the slope-compensation
signal, R CSSC is the value of the resistor connected
between CSSC and CS used to program the ramp rate,
and f SW is the switching frequency.
Error Amplifier
The MAX5974A/MAX5974B include an internal error
amplifier with a sample-and-hold input. The feedback
input of the MAX5974C/MAX5974D is continuously con-
nected. The noninverting input of the error amplifier is
connected to the internal reference and feedback is
provided at the inverting input. High open-loop gain and
unity-gain bandwidth allow good closed-loop bandwidth
and transient response. Calculate the power-supply out-
put voltage using the following equation:
R + R
R FB2
where V REF = 1.52V for the MAX5974A/MAX5974B
and V REF = 1.215V for the MAX5974C/MAX5974D. The
amplifier’s noninverting input is internally connected to
a soft-start circuit that gradually increases the reference
voltage during startup. This forces the output voltage to
and does not start. Use a low-leakage capacitor for C IN .
Typically, offline power supplies keep startup times to
less than 500ms even in low-line conditions (85V AC
input for universal offline or 36V DC for telecom applica-
tions). Size the startup resistor, R IN , to supply both the
maximum startup bias of the device (150 F A) and the
charging current for C IN . C IN must be charged to 16V
within the desired 500ms time period. C IN must store
enough charge to deliver current to the device for at
least the soft-start time (t SS ) set by C SS . To calculate the
approximate amount of capacitance required, use the
following formula:
I G = Q GTOT f SW
(I + I )(t )
V HYST
where I IN is the ICs’ internal supply current (1.8mA)
after startup, Q GTOT is the total gate charge for the
n-channel and p-channel FETs, f SW is the ICs’ switch-
ing frequency, V HYST is the bootstrap UVLO hysteresis
(9V typ), and t SS is the soft-start time. R IN is then cal-
culated as follows:
come up in an orderly and well-defined manner under
all load conditions.
R IN ?
V S(MIN) ? V INUVR
I START
where V S(MIN) is the minimum input supply voltage for
the application (36V for telecom), V INUVR is the boot-
strap UVLO wake-up level (16V), and I START is the IN
supply current at startup (150 F A max).
Maxim Integrated
21
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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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