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參數(shù)資料
| 型號(hào)： | MAX1678 |
| 廠商： | Maxim Integrated Products, Inc. |
| 元件分類： | DC/DC變換器 |
| 英文描述： | 1-Cell to 2-Cell, Low-Noise, High-Efficiency, Step-Up DC-DC Converter |
| 中文描述： | 1節(jié)至2節(jié)電池、低噪聲、高效率、升壓型DC-DC轉(zhuǎn)換器 |
| 文件頁(yè)數(shù)： | 11/12頁(yè) |
| 文件大?。?/td> | 166K |
| 代理商： | MAX1678 |
Capac itor S elec tion
Choose input and output capacitors to service input
and output peak currents with acceptable voltage rip-
ple. Capacitor ESR is a major contributor to output rip-
ple (usually more than 60%). A 10μF, ceramic output
filter capacitor typically provides 50mV output ripple
when stepping up from 1.3V to 3.3V at 20mA. Low input
to output voltage differences (i.e., 2 cells to 3.3V)
require higher capacitor values (10μF to 47μF).
The input filter capacitor (C
IN
) also reduces peak cur-
rents drawn from the battery and improves efficiency.
Low-ESR capacitors are recommended. Ceramic
capacitors have the lowest ESR, but low-ESR tantalums
represent a good balance between cost and perfor-
mance. Low-ESR aluminum electrolytic capacitors are
tolerable, and standard aluminum electrolytic capaci-
tors should be avoided. Capacitance and ESR variation
over temperature need to be taken into consideration
for best performance in applications with wide operat-
ing temperature ranges. Table 2 lists suggested capac-
itors and suppliers.
Minimizing Noise and V oltage Ripple
EMI and output voltage ripple can be minimized by fol-
lowing these simple design rules:
1) Place the DC-DC converter and digital circuitry on
the opposite corner of the PC board from sensitive
RF and analog input stages.
2) Use a closed-core inductor, such as toroid or
shielded bobbin, to minimize fringe magnetic fields.
3) Choose the largest inductor value that satisfies the
load requirement, to minimize peak switching cur-
rent and the resulting ripple and noise.
4) Use low-ESR input and output filter capacitors.
5) Follow sound circuit-board layout and grounding
rules (see the PC Board Layout and Grounding sec-
tion).
PC Board Layout and Grounding
High switching frequencies and large peak currents
make PC board layout an important part of design.
Poor design can result in excessive EMI on the feed-
back paths and voltage gradients in the ground plane.
Both of these factors can result in instability or regula-
tion errors. The OUT pin must be bypassed directly to
GND, as close to the IC as possible (within 0.2 inches
or 5mm).
Place power components—such as the MAX1678,
inductor, input filter capacitor, and output filter capaci-
tor—as close together as possible. Keep their traces
short, direct, and wide (
≥
50 mil or 1.25mm), and place
their ground pins close together in a star-ground con-
figuration. Keep the extra copper on the board and
integrate it into ground as a pseudo-ground plane. On
multilayer boards, route the star ground using compo-
nent-side copper fill, then connect it to the internal
ground plane using vias.
Place the external voltage-feedback network very close
to the FB pin (within 0.2 inches or 5mm). Noisy traces,
such as from the LX pin, should be kept away from the
voltage-feedback network and separated from it using
grounded copper. The MAX1678 evaluation kit manual
shows an example PC board layout, which includes a
pseudo-ground plane.
M
1-Cell to 2-Cell, Low-Noise,
High-Effic ienc y, S tep-Up DC-DC Converter
______________________________________________________________________________________
11
Table 2. Recommended Surface-Mount Capacitor Manufacturers
603-224-1961
PHONE
VALUE
(μF)
595D-series tantalum
DESCRIPTION
Sprague
MANUFACTURER
803-946-0690
AVX
TAJ , TPS-series tantalum
4.7 to 47
803-946-0690
AVX
X7R ceramic
4.7 to 10
847-390-4373
TDK
X7R ceramic
4.7 to 22
408-573-4150
Taiyo Yuden
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1678ESA | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1678EUA | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| MAX1678EUA+ | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 1-2 Cell Step-Up DC/DC Converter RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| MAX1678EUA+T | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 1-2 Cell Step-Up DC/DC Converter RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| MAX1678EUAT | 制造商:Maxim Integrated Products 功能描述: |
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