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| 型号： | MAX8655ETN+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 16/23页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 25A 56TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 37 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.7 V ~ 5.5 V |
| 输入电压： | 4.5 V ~ 25 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 200kHz ~ 1MHz |
| 电流 - 输出： | 25A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 56-WFQFN 裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 56-TQFN-EP（8x8） |
Highly Integrated, 25A, Wide-Input,
Internal MOSFET, Step-Down Regulator
Setting the Current Limit
Valley Current Limit
The MAX8655 has an adjustable valley current limit, con-
R ILIM 1 =
7.5 × V TH
10 μ A
I LIM = ? P ? P
R FOBK =
figurable for foldback with automatic recovery, or con-
stant-current limit with latch-up. To set the constant-
current limit for the latch-up mode, connect a single
resistor R ILIM2 from ILIM2 to GND. For latch-up current-
limit mode, set R ILIM2 equal to R VALLEY obtained from
the R VALLEY vs. Valley Current Limit graph in the Typical
Operating Characteristics section for the required valley
current I VALLEY . I VALLEY is the value of the inductor val-
ley current at maximum load (I LOAD(MAX) - 1 / 2 I P-P )
To set the current limit for foldback mode, connect a
resistor from ILIM2 to the output (R FOBK ), and another
resistor from ILIM2 to GND (R ILIM2 ). See Figure 7. The
values of R FOBK and R ILIM2 are calculated as follows.
First, select the percentage of foldback (P FB ). This per-
centage corresponds to the current limit when V OUT
equals zero divided by the current limit when V OUT
equals its nominal voltage. A typical value of P FB is in
the 15% to 40% range. A lower value of P FB yields
lower short-circuit current. The following equations are
used to calculate R FOBK and R ILIM2 :
P FB × V OUT
I ILIM 2 × ( 1 ? P FB )
This allows a maximum DC output current of:
V TH I
R L 2
where R L is the DC resistance of the inductor.
To ensure maximum output current, use the minimum
value of V TH from each setting, and the maximum R L
values at the highest expected operating temperature.
The DC resistance of the inductor’s copper wire has a
+0.38%/°C temperature coefficient.
An RC circuit is connected across the inductor (see
Figure 8). The RC time constant is set to be 1.1 to 1.2
times the inductor (L/R L ) time constant. Pick the value
of C9 in the 0.1μF to 0.47μF range, and then calculate
R1 from:
R1 = 1.2L/(R L x C9)
Add a resistor (R2 in Figure 8) to the CS- connection to
minimize input offset error. Calculate the value of R2 as
follows:
? When V OUT ≥ 2.4V:
? 20 μ A +
? × R 1
R ILIM 2 =
I ILIM 2 × R VALLEY × R FOBK
V OUT + ( I ILIM 2 × ( R FO B K ? R VALLEY ) )
R 2 =
?
?
R ILIM1 × 10 μ A ?
32 k ? ?
20 μ A
R 2 =
? 15 μ A +
32 k ?
?
?
where I ILIM2 is 5μA.
If the resulting value of R ILIM2 is negative, increase P FB .
Peak Current Limit
The peak current-limit threshold (V TH ) is set by a resistor
connected from ILIM1 to GND (R ILIM1 ). V TH corresponds
to the peak voltage across the sensing element (inductor
or current-sense resistor). R ILIM1 is calculated as follows:
? When V OUT < 2.4V:
15 μ A x R 1
? R ILIM1 x 10 μ A ?
?
LX
OUT
LX
L1
V OUT
MAX8655
R FOBK
MAX8655
R1
C9
ILIM2
CS+
C10
R2
C11
Figure 7. ILIM2 Resistor Connections
R ILIM2
CS-
Figure 8. Current Sense Using the Inductor’s DC Resistance
16
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8655ETN/GG8 | 功能描述:直流/直流开关调节器 RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MAX8655ETN+ | 功能描述:直流/直流开关调节器 25A Int MOSFET Step-Down Regulator RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MAX8655ETN+T | 功能描述:直流/直流开关调节器 25A Int MOSFET Step-Down Regulator RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MAX8655ETN+TW | 功能描述:直流/直流开关调节器 25A Int MOSFET Step-Down Regulator RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MAX8655ETN+W | 功能描述:直流/直流开关调节器 25A Int MOSFET Step-Down Regulator RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
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