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参数资料
| 型号： | MAX17500AEVKIT+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 11/18页 |
| 文件大小： | 0K |
| 描述： | KIT EVALUATION FOR MAX17500 |
| 标准包装： | 1 |
| 主要目的： | DC/DC 转换器 |
| 输出及类型： | 2，隔离 |
| 输出电压： | 5V，15V |
| 电流 - 输出： | 1.5A，100mA |
| 输入电压： | ±36 V ~ 72 V |
| 稳压器拓扑结构： | 回扫 |
| 频率 - 开关： | 350kHz |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | MAX17500A |
Current-Mode PWM Controllers with
Programmable Switching Frequency
Soft-Start
The devices’ soft-start feature allows the output voltage
to ramp up in a controlled manner, eliminating voltage
overshoot. The devices ’ reference generator that is
internally connected to the error amplifier soft-starts to
achieve superior control of the output voltage under
heavy- and light-load conditions. Soft-start begins after
UVLO is deasserted (V IN is above 21.6V for the
MAX17500, V IN is above 9.5V for the MAX17499, and
the voltage on UVLO/EN is above 1.23V). The voltage
applied to the noninverting node of the amplifier ramps
from 0 to 1.23V in 1984 NDRV switching cycles. Use the
following formula to calculate the soft-start time (t SS ):
MAX17499/MAX17500 fig04
100mA LOAD ON/V OUT1
100mA LOAD ON/V OUT2
V OUT
2V/div
t SS =
1984
f NDRV
2ms/div
Figure 4. Primary-Side Output Voltage Soft-Start During Initial
R 15 = 88 . 9 × ( R 12 ) 4
where f NDRV is the switching frequency at the NDRV
output. Figure 4 shows the soft-start regulated output of
a power supply using the MAX17500 during startup.
n-Channel MOSFET Switch Driver
The NDRV output drives an external n-channel MOSFET.
The internal regulator output (V CC ), set to approximately
9V, drives NDRV. For the universal input voltage range,
the MOSFET used must withstand the DC level of the
high-line input voltage plus the reflected voltage at the
primary of the transformer. Most applications that use the
discontinuous flyback topology require a MOSFET rated
at 600V. NDRV can source/sink in excess of 650mA/
1000mA peak current; therefore, select a MOSFET that
mA yields acceptable conduction and switching losses.
Oscillator/Switching Frequency
Use an external resistor at RT to program the devices’
internal oscillator frequency between 50kHz and 2.5MHz.
The MAX17499A/MAX17500A output switching frequen-
cy is one-half the programmed oscillator frequency with a
Startup for the Circuit in Figure 6
where R12 is the resistor connected from RT to GND
(see Figure 1).
Connect an RC network in parallel with R12 as shown in
Figure 1. The RC network should consist of a 100nF
capacitor, C6, (for stability) in series with resistor R15,
which serves to further minimize jitter. Use the following
formula to determine the value of R15:
1
For example, if R12 is 4k Ω , R15 becomes 707 Ω .
Internal Error Amplifier
The devices include an internal error amplifier to regu-
late the output voltage in the case of a nonisolated
power supply (see Figure 1). For the circuit in Figure 1,
calculate the output voltage using the following equation:
V OUT = ? 1 +
50% duty cycle. The MAX17499B/MAX17500B output
switching frequency is one-quarter of the programmed
oscillator frequency with a 75% duty cycle.
?
?
R13 ?
R 14 ? ?
V REF
The MAX17499A/MAX17500A and MAX17499B/
MAX17500B have programmable output switching fre-
quencies from 25kHz to 625kHz and 12.5kHz to
625kHz, respectively. Use the following formulas to
determine the appropriate value of resistor R12 (see
Figure 1) needed to generate the desired output
switching frequency (f SW ) at the NDRV output:
where V REF = 1.23V. The amplifier’s noninverting input
is internally connected to a digital soft-start circuit that
gradually increases the reference voltage during start-
up applied to this input. This forces the output voltage
to come up in an orderly and well-defined manner
under all load conditions.
The error amplifier may also be used to regulate the ter-
R 12 =
R 12 =
10 10
2 f SW
10 10
4 f SW
for the MAX 17499 A MAX 17500 A .
for the MAX 17499 B MAX 17500 B .
tiary winding output, which implements a primary-side-
regulated, isolated power supply (see Figure 6). For the
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX17500AEVKIT+ | 功能描述:电流型 PWM 控制器 w/Prog Switch Frequency 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 |
| MAX17500BAUB+ | 功能描述:电流型 PWM 控制器 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 |
| MAX17500BAUB+T | 功能描述:电流型 PWM 控制器 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 |
| MAX17500BEUB+ | 功能描述:电流型 PWM 控制器 w/Prog Switch Frequency 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 |
| MAX17500BEUB+T | 功能描述:电流型 PWM 控制器 w/Prog Switch Frequency 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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