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参数资料
| 型号： | MAX8540EEE+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 11/16页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR PWM CM 16-QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 100 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 1MHz |
| 占空比： | 82% |
| 电源电压： | 7.6 V ~ 18 V |
| 降压： | 无 |
| 升压： | 无 |
| 回扫： | 是 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 是 |
| Cuk： | 无 |
| 隔离： | 是 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 管件 |
Synchronizable, High-Frequency Current- and
Voltage-Mode PWM Controllers for Isolated Supplies
where R PRAMP is in k ? . The ramp-voltage magnitude is
independent of frequency. The range of values for
R PRAMP is from 12.4k ? to 42k ? .
Soft-Start
The soft-start feature allows converters built using the
MAX8540/MAX8541 to apply power to the load in a
controllable soft ramp, thus reducing startup surges
and stresses. It also determines power-up sequencing
when several converters are used.
Upon power turn-on, the soft-start pin acts as a current
sink to discharge any capacitance connected to it. Once
the voltage at V CC has exceeded its lockout value, soft-
start then charges the external capacitor (C SS ), allowing
the converter output voltage to ramp up. Full output volt-
age is reached in approximately 440ms/μF.
Current Limit
The MAX8540/MAX8541 utilize two current-limit
schemes: cycle-by-cycle current limit and short-circuit
current limit. Set the current-limit threshold using a
resistor-divider from REF to GND with ILIM connected to
the center. The current-limit threshold is determined as:
the ILIM threshold voltage. Once the voltage on SKTON
reaches its threshold voltage, the MAX8540/MAX8541
begin skipping switching cycles for a time determined
by the capacitance connected to SKTOFF. Once this
time period has elapsed, the IC begins to switch for the
time period set by the capacitance connected to
SKTON. This process continues until the output short is
removed. See the SKTON and SKTOFF section for
details on setting the hiccup-mode periods.
Connect SKTOFF to REF and SKTON to GND to disable
the latched-mode and hiccup-mode protection, and
operate continuously in cycle-by-cycle current-limit.
PMW Comparator
The PWM comparator of the MAX8540 transforms the
optocoupled error voltage (V OPTO ) into a duty cycle by
comparing the opto feedback-error voltage with a
summed voltage. The summed voltage is the sum of
the programmable slope compensation and the cur-
rent-sense voltages. When the summed voltage
exceeds the opto feedback error voltage, the gate-
drive logic turns off the external MOSFET.
The PWM comparator in the MAX8541 compares
V ILIM =
R 5
R 5 + R 6
× V REF
V OPTO with the programmable voltage ramp. When the
voltage ramp exceeds V OPTO , the gate-driver logic
turns off the external MOSFET.
where R5 is the resistor from ILIM to GND and R6 is the
resistor from REF to ILIM. Use 240k ? for R16 and vary
R23 to change the threshold.
The CS signal provides feedback on the current ramp
through the main external MOSFET. The voltage on CS
is monitored by the IC. The cycle-by-cycle current limit
abbreviates the on-time of the external MOSFET in the
event that the voltage at CS is greater than the thresh-
old voltage set by ILIM.
The current-limit feature protects against a hard short
or overcurrent fault at the output by one of two selected
protection modes: by latching off the output, or pulsing
the output to reduce the average output current
(hiccup mode).
To select latched mode, connect SKTOFF to REF. In
this mode, if the hard short exists for the time period set
by the capacitance at SKTON, the output is latched off.
To unlatch the output, toggle EN or cycle the input
power to V CC .
To select hiccup mode, connect capacitors to SKTON
and SKTOFF to program the hiccup mode on- and off-
times. When a cycle-by-cycle event is detected, the IC
charges the capacitor at SKTON. The capacitor contin-
ues to charge as long as the CS voltage is greater than
SKTON and SKTOFF
The capacitance, C SKTON , determines the time period
allowed before the short-circuit current limit initiates.
Once the CS voltage exceeds the ILIM threshold, the
capacitor at SKTON begins to charge. The capacitor
continues to charge until the SKTON threshold voltage
is reached or the overcurrent event is removed. This
feature allows for the higher currents required during
startup with high-capacitance loads. Set C SKTON to
allow sufficient time for startup. The required capaci-
tance at SKTON is determined as:
C SKTON = t ON / 10 3
where t ON is in ms and C SKTON is in μF. The allowable
range for C SKTON is 100pF to 0.01μF.
The capacitance at SKTOFF determines the time period
that the external MOSFET is turned off during an over-
current event. Once the SKTON time period is exceeded,
the SKTOFF capacitor charges. Once V SKTOFF reaches
its threshold, the IC begins to switch again. C SKTOFF is
determined as:
C SKTOFF = t OFF / 10 3
where t OFF is in ms and C SKTOFF is in μF. The allow-
able range for C SKTOFF is 1000pF to 1μF.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8540EEE+ | 功能描述:电流型 PWM 控制器 Synchronizable 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 |
| MAX8540EEE+T | 功能描述:电流型 PWM 控制器 PWM Controller Curr-Mode 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 |
| MAX8540EEE-T | 功能描述:电流型 PWM 控制器 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 |
| MAX8541EEE | 功能描述:电压模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| MAX8541EEE+ | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
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