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参数资料
| 型号： | MAX8686EVKIT+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 17/23页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL FOR MAX8686 |
| 标准包装： | 1 |
| 主要目的： | DC/DC，步降 |
| 输出及类型： | 1，非隔离 |
| 输出电压： | 0.7 V ~ 5.5 V |
| 电流 - 输出： | 25A |
| 输入电压： | 4.5 V ~ 20 V |
| 稳压器拓扑结构： | 降压 |
| 频率 - 开关： | 300kHz ~ 1MHz |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | MAX8686 |
Single/Multiphase, Step-Down,
DC-DC Converter Delivers Up to 25A Per Phase
Design Procedures
Setting the Output Voltage
robust current-mode control. The following equation
can be used as a guideline.
To set the output voltage for the MAX8686, connect
REFIN to the center of an external resistor-divider from
PHASE/REFO to GND (R3 and R4 of Figures 2, 3, or 4).
I OUT _ MAX
N
× LIR × R DC ≥ 10 mV
The sum of R3 and R4 should exceed 165k ? .
Preselect R4 and calculate R3 using the following
equation:
where R DC is the sense resistance value of the inductor
or sense resistor at the highest operating temperature.
It is also important to choose lower LIR to keep the cur-
R 3 = R 4 × ?
? 1 ?
? 3 . 3
? V OUT
?
?
rent-sense signal below 45mV, which is the maximum
current limit:
? 1 +
? x R DC ≤ 45 mV
where V OUT is the desired output voltage and 3.3V
comes from the reference voltage (V PHASE/REFO ). The
I OUT _ MAX ?
N ?
LIR
2
?
?
resistor-divider should be placed as close as possible to
REFIN. If an external reference is used, see the
Reference Output (PHASE/REFO)/Reference Input
(REFIN) section for more details.
Inductor Selection
The output inductor is selected based on the desired
amount of inductor ripple current. A larger inductance
value minimizes output ripple current and increases
If this condition is not met, then the LIR must be adjust-
ed or the input signal to the current-sense amplifier
must be scaled down with a resistor-divider.
Setting the Switching Frequency
To set the switching frequency, connect a capacitor
from FREQ to GFREQ. Calculate the capacitor value
from the following equation:
efficiency but slows down the output-inductor-current
slew rate during a load transient. LIR is the ratio of rip-
ple current to the total current per phase. For the best
C FREQ =
5 x 10 5 ? 30 x f SW
2 . 7 x f SW
tradeoff of efficiency and transient response, an LIR of
30% to 60% is recommended (LIR = 0.3 to 0.6).
Choose a higher LIR when more phases are used to
take advantage of ripple-current cancellation. The
inductor value is determined from:
where f SW is the desired switching frequency in kilo-
hertz and C FREQ is the total capacitance in picofarads.
The operating frequency range is from 300kHz to
1MHz, so the capacitance at FREQ should be between
600pF and 180pF. Parasitic capacitance from device
L ≥
V OUT × ( 1 ? D ) × N
LIR × f SW × I OUT _ MAX
pads and PCB layout should be deducted from the
above calculation especially at high switching frequen-
cies. In the estimation of parasitic capacitance, 15pF
I PEAK = × ? 1 + ?
x ( V OUT ? 0 . 1 8 2 x V IN _ MIN )
1 . 22 x 10 7 R DC
where f SW is the per-phase switching frequency,
I OUT_MAX is the maximum-rated output current, D is the
duty ratio (V OUT /V IN ), N is the number of phases, and
V OUT is the output voltage. The selected inductor
should have low DC resistance, and the saturation cur-
rent should be greater than the peak inductor current,
I PEAK . I PEAK is found from:
I OUT _ MAX ? LIR ?
N ? 2 ?
When the DC resistance (R DC ) of the output inductor is
used for current sensing, the DC resistance should be
selected to ensure a sufficient current-sense signal for
per phase should be used. GFREQ may be connected
to GND (quiet ground).
Setting the Slope Compensation
For most applications where the duty cycle is less than
40%, set EN/SLOPE = 1.25V. For applications with a
duty cycle greater than 40%, set the slope compensa-
tion with a resistor (R SLOPE ) from EN/SLOPE to GND.
Calculate the R SLOPE using the following formula:
R SLOPE =
f SW x L
where R DC is the DC resistance of the inductor,
V IN_MIN is the minimum operating input voltage, and
f SW is the switching frequency.
______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8686EVKIT# | 功能描述:电源管理IC开发工具 MAX8686 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 |
| MAX8686EVKIT+ | 功能描述:电源管理IC开发工具 MAX8686 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 |
| MAX8687ETL+ | 制造商:Maxim Integrated Products 功能描述:SINGLE /MULTIPHASE, DC/DC CONVERTER - Rail/Tube |
| MAX8688AHETG+ | 功能描述:电流和电力监控器、调节器 Digital Power-Supply Controller/Monitor RoHS:否 制造商:STMicroelectronics 产品:Current Regulators 电源电压-最大:48 V 电源电压-最小:5.5 V 工作温度范围:- 40 C to + 150 C 安装风格:SMD/SMT 封装 / 箱体:HPSO-8 封装:Reel |
| MAX8688AHETG+T | 功能描述:电流和电力监控器、调节器 Digital Power-Supply Controller/Monitor RoHS:否 制造商:STMicroelectronics 产品:Current Regulators 电源电压-最大:48 V 电源电压-最小:5.5 V 工作温度范围:- 40 C to + 150 C 安装风格:SMD/SMT 封装 / 箱体:HPSO-8 封装:Reel |
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