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参数资料
| 型号： | MAX1642 |
| 厂商： | Maxim Integrated Products, Inc. |
| 元件分类： | DC/DC变换器 |
| 英文描述： | High-Efficiency, Step-Up DC-DC Converters for 1V Inputs |
| 中文描述： | 高效率、升压型DC-DC转换器、输入可低至1V |
| 文件页数： | 8/12页 |
| 文件大小： | 130K |
| 代理商： | MAX1642 |
M
High-Effic ienc y, S tep-Up
DC-DC Converters for 1V Inputs
8
_______________________________________________________________________________________
BATTLO
(MAX 1643)
The MAX1643 contains an on-chip comparator for low-
battery detection. If the voltage at BATT drops below
1V,
BATTLO
sinks current.
BATTLO
is an open-drain
output. In combination with PFI/
PFO
, this allows moni-
toring of both the input and output voltages.
Reverse-Battery Protec tion
The MAX1642/MAX1643 can sustain/survive single-cell
battery reversal up to the package power-dissipation
limit. An internal 5
resistor in series with a diode limits
reverse current to less than 220mA, which prevents dam-
age to the MAX1642/MAX1643. Prolonged operation
above 220mA reverse-battery current can degrade the
devices’ performance.
________________Design Information
Output V oltage S elec tion
The MAX1642/MAX1643 operate with a 3.3V ±4% or
adjustable output. To select fixed-voltage operation, con-
nect FB to GND. For an adjustable output between 2V
and 5.2V, connect FB to a resistor voltage divider
between OUT and GND (Figure 4). FB regulates to 1.23V.
Since FB leakage is 10nA max, select feedback resistor
R2 in the 100k
to 1M
range. R1 is given by:
where V
REF
= 1.23V.
Power-Fail Detec tion
The MAX1642/MAX1643 have an on-chip comparator for
power-fail detection. This comparator can detect loss of
power at the input or output. If the voltage at PFI falls
below 614mV, the
PFO
output sinks current to GND.
Hysteresis at the power-fail input is 1%. The power-fail
monitor’s threshold is set by two resistors: R3 and R4
(Figure 5). Set the threshold using the following equation:
where V
TH
is the desired threshold of the power-fail
detector, and V
PFI
is the 614mV reference of the power-
fail comparator. Since PFI leakage is 10nA max, select
feedback resistor R4 in the 100k
to 1M
range.
Low-Battery S tart-Up
The MAX1642/MAX1643 are bootstrapped circuits with
a low-voltage start-up oscillator. They can start under
low-load conditions at lower battery voltages than at full
load. Once started, the output can maintain the load as
the battery voltage decreases below the start-up volt-
age (see Typical Operating Characteristics).
Induc tor S elec tion
A 100μH inductor is recommended for most appli-
cations. The use of lower inductor values (down to
68μH) increases maximum output current. Higher val-
ues (up to 220μH) reduce peak inductor current and
consequent ripple and noise. The inductor’s saturation-
current rating must exceed the peak current limit syn-
thesized by the MAX1642/MAX1643’s timing
algorithms:
= K
L
MIN
where K
MAX
= 35V-μs. The maximum recommended
I
PEAK
is 350mA. For best efficiency, inductor series
resistance should be less than 1
.
I
PEAK
MAX
R3 = R4
V
V
- 1
TH
PFI
R1 = R2
V
V
- 1
OUT
REF
MAX1642
GND
FB
BATT
PFI
3.3V
OUT
0.88V to 1.65V INPUT
100
μ
H, 350mA
PF0
22
μ
F
0.1
μ
F
SHDN
LX
OUT
OUT
22
μ
F
0.1
μ
F
MAX1643
GND
FB
BATT
3.3V
OUT
0.88V to 1.65V INPUT
BATTLO
22
μ
F
0.1
μ
F
LX
OUT
PFI
PFO
22
μ
F
0.1
μ
F
OUT
100
μ
H, 350mA
Figure 2. MAX1642 3.3V Standard Application Circuit
Figure 3. MAX1643 3.3V Standard Application Circuit
相关PDF资料 |
PDF描述 |
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| MAX1642EUA | High-Efficiency, Step-Up DC-DC Converters for 1V Inputs |
| MAX1643EUA | High-Efficiency, Step-Up DC-DC Converters for 1V Inputs |
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1642EUA | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1642EUA+ | 功能描述:直流/直流开关转换器 Integrated Circuits (ICs) RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1642EUA+T | 功能描述:直流/直流开关转换器 Integrated Circuits (ICs) RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1642EUA-T | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1642EVKIT | 功能描述:电源管理IC开发工具 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 |
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