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参数资料
| 型号： | MAX5974EETE+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 19/22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% |
| 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 |
MAX5974E/MAX5974F
Current-Mode PWM Controllers for
Low-Cost Flyback Supplies
4 R RT
Oscillator Synchronization
The internal oscillator can be synchronized to an external
clock by applying the clock to DITHER/SYNC directly. The
external clock frequency can be set anywhere between
1.1x to 2x the internal clock frequency.
Using an external clock increases the maximum duty
cycle by a factor equal to f SYNC /f SW . This factor should
be accounted for in setting the maximum duty cycle
using any of the methods described in the Duty-Cycle
Clamping section. The formula below shows how the
maximum duty cycle is affected by the external clock
frequency:
=
%DITHER ×
3 R DITHER
where %DITHER is the amount of dither expressed as a
percentage of the switching frequency. Setting R DITHER
to 10 x R RT generates Q 10% dither.
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-
D =
× SYNC
MAX
V MIN f
2.43V f SW
sense signal for stability of the peak current-mode
control loop. The ramp rate of the slope compensation
signal is given by:
where V MIN is described in the Duty-Cycle Clamping
section, f SW is the switching frequency as set by the
resistor connected between RT and GND, and f SYNC is
the external clock frequency.
m =
R CSSC × 50 μ A × f SW
80%
f TRI =
V OUT REF × FB1 FB2
= V
Frequency Dithering for Spread-
Spectrum Applications (Low EMI)
The switching frequency of the converter can be dith-
ered in a range of Q 10% by connecting a capaci-
tor from DITHER/SYNC to GND, and a resistor from
DITHER/SYNC to RT as shown in the Typical Application
Circuit . This results in lower EMI.
A current source at DITHER/SYNC charges the capaci-
tor C DITHER to 2V at 50 F A. Upon reaching this trip point,
it discharges C DITHER to 0.4V at 50 F A. The charging
and discharging of the capacitor generates a triangular
waveform on DITHER/SYNC with peak levels at 0.4V and
2V and a frequency that is equal to:
50 μ A
C DITHER × 3.2V
Typically, f TRI should be set close to 1kHz. The resistor
R DITHER connected from DITHER/SYNC to RT deter-
mines the amount of dither as follows:
Maxim Integrated
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 MAX5974_ include an internal error amplifier for
primary feedback. The noninverting input of the error
amplifier is connected to the internal reference and feed-
back 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 output voltage using the following equation:
R + R
R FB2
where V REF = 1.215V. The amplifier’s noninverting input
is internally connected to a soft-start circuit that gradu-
ally increases the reference voltage during startup. This
forces the output voltage to come up in an orderly and
well-defined manner under all load conditions.
19
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 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 |
| MAX5974FETE+ | 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 |
| MAX5974FETE+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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