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参数资料
| 型号： | MAX8686EVKIT# |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 18/23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
Setting the Peak Current Limit
The peak current-limit threshold (V CS+ - V CS- ) is set by
a resistor connected from ILIM to GND. An internal
10μA current source flows through this resistor to set a
voltage that is 61 times higher than the current-limit
threshold. For example, a 300k ? resistor sets the cur-
rent-limit threshold at (10μA x 300k ? )/61 or 49mV:
Calculating the Phase Voltage
In the multiphase converter, the phases are interleaved
to reduce the output voltage ripple. The master starts
conduction at the beginning of the FREQ ramp. The
phase delay time, t PHASE , is the conduction delay time
of slaves from the master. Determine the phase delay
time as follows:
V TH = V CS + ? V CS ? =
10 x R ILIM
61
t PHASEX =
X
f SW x 10 3 x N
where R ILIM is in kilohms, V TH is in millivolts, and corre-
sponds to the peak voltage across the sensing element
(inductor resistance or current-sense resistor).
This allows a maximum average DC output current of
where X is the number of the slave (X = 1 to 5 for 6
phase converters) f SW is the switching frequency per
phase in kilohertz, and N is the total number of phases.
Calculate the phase voltage of each slave from:
I LIM = TH ? P ? P
R DC
V PHASEX = PHASEX
(ILIM):
V I
2
t x 5 x 10 8 ? 30
C FREQ
where C FREQ is the total capacitance (in picofarads) at
where R DC is the DC resistance of the inductor or sense
resistor and I P-P is the peak-to-peak inductor current.
To ensure maximum output current, use the minimum
value of V TH from each setting and the maximum R DC
values at the highest expected operating temperature.
The DC resistance of the inductor’s copper wire has a
+0.38%/°C temperature coefficient.
FREQ (see the Setting the Switching Frequency sec-
tion). For better jitter immunity, V PHASE should be limit-
ed between 0.3V and 2.5V.
Then determine resistor-divider for each slave.
Preselect more than 10k ? for phase resistor RX5 (X = 2
to 6, R25, R35, R45, R55, and R65) in Figure 4, and cal-
culate RX4 (R24, R34, R44, R54, and R64) as follows:
When using a sense resistor, the current through the
sense resistor sets a voltage compared with the peak
current limit.
RX 4 = RX 5 ×
5.4 V ? V PHASE( X )
V PHASE ( X )
To provide a more efficient and lower cost design, the
current can be measured through the inductor using a
DCR method (voltage across the DC resistance of the
inductor) as shown in Figure 5.
An RC circuit is connected across the inductor. The RC
time constant is set to be 1.1 to 1.2 times the inductor
Input Capacitor
The input capacitor reduces the peak current drawn
from the power source and reduces the noise and volt-
age ripple on the input DC voltage bus caused by the
circuit’s switching. The input capacitors must meet the
time constant (L/R DC ). Pick the value of C1 in the 1μF to
4.7μF range, and then calculate R1 from:
L1
R 1 =
1 . 2 x L 1
R DC x C 1
LX
R1
V OUT
C1
R2 is added in some applications to scale down the
current signal. R2 and LIR should be selected to meet
the following condition.
MAX8686
CS+
R2
I OUT _ MAX
N
?
x ? 1 +
?
LIR ?
? x R DC x
2 ?
R 2
R 1 + R 2
≤ 45 mV
CS-
Figure 5. Current Sense Using the Inductor’s DC Resistance
18
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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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