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參數(shù)資料
| 型號： | MAX849 |
| 廠商： | Maxim Integrated Products, Inc. |
| 元件分類： | DC/DC變換器 |
| 英文描述： | Low-Noise, Step-Up DC-DC Converters(高功率，低噪，帶0.5AMOSFET功率開關,步升DC-DC變換器) |
| 中文描述： | 1至3節(jié)電池、大功率、低噪聲、升壓型DC-DC轉(zhuǎn)換器 |
| 文件頁數(shù)： | 13/16頁 |
| 文件大?。?/td> | 192K |
| 代理商： | MAX849 |
M
1-Cell to 3-Cell, High-Power,
Low-Noise, S tep-Up DC-DC Converters
______________________________________________________________________________________
13
Capac itor S elec tion
Input Bypass Capacitors
A 22μF, low-ESR input capacitor will reduce peak cur-
rents and reflected noise due to inductor current ripple.
Smaller ceramic capacitors may also be used for light
loads or in applications that can tolerate higher input
ripple.
Output Filter Capacitors
Two 100μF (single 100μF for the MAX848), 10V, low-
ESR, output filter capacitors typically exhibit 30mV rip-
ple when stepping up from 1.2V to 3.3V at 200mA
(100mA for the MAX848). Bypass the MAX848/MAX849
supply input, OUT, with a 0.1μF ceramic capacitor
to GND. Also bypass POUT to PGND with a 0.1μF
ceramic capacitor.
The filter capacitors’ equivalent series resistance (ESR)
affects efficiency and output ripple. The output voltage
ripple is the product of the peak inductor current and
the output capacitor’s ESR. Low-ESR, surface-mount
tantalum capacitors are currently available from
Sprague (595D series) and AVX (TPS series). Sanyo
OS-CON organic-semiconductor, through-hole capaci-
tors also exhibit very low ESR, and are especially useful
for operation at cold temperatures. See Table 5 for a list
of suggested capacitor suppliers.
__________Applic ations Information
Using a Momentary On/Off S witc h
A momentary pushbutton switch can be used to turn
the MAX848/MAX849 on and off.
As shown in Figure 9, ON1 is pulled low and
ON2
is
pulled high when the part is off. When the momentary
switch is pressed,
ON2
is pulled low and the regulator
turns on. The switch should be on long enough for the
μC to exit reset. The controller issues a logic high to
ON1, which guarantees that the part will stay on,
regardless of the switch state.
To turn off the regulator, the switch is pressed and held.
The controller reads the switch status and pulls ON1
low. The switch is released and
ON2
is pulled high.
Power Amplifier (PA) and Radio S upply
in a T ypic al Phone Applic ation
The MAX849 is an ideal power supply for the power
amplifier (PA) and the radio used in digital cordless
and PCS phones (Figure 10). The PA is directly pow-
ered by the MAX849 for maximum output swing. Post-
linear regulators power the controller and the radio. In
addition, they reduce switching noise and ripple. Table
3 lists the output power available when operating with
one or more NiCd/NiMH cells or one Li-Ion cell.
MAX848
MAX849
ON2
ON1
V
DD
I/O
I/O
OUT
μ
C
1M
1M
Figure 9. Momentary Pushbutton On/Off Switch
MAX848
MAX849
μ
C
MAX8865/MAX8866 DUALS
MAX8863/MAX8864 SINGLES
RADIO
PA
Figure 10. Typical Phone Application
NUMBER OF CELLS
INPUT VOLTAGE
(V)
OUTPUT VOLTAGE:
PA POWER SUPPLY
(V)
3.3
3.3
5.0
5.0
OUTPUT POWER
(W)
1 NiCd/NiMH
2 NiCd/NiMH
2 NiCd/NiMH
3 NiCd/NiMH or 1 Li-Ion
1.2
2.4
2.4
3.6
0.9
2.4
2.6
4.3
Table 3. Available Output Power
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相關代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX849ESE | 功能描述:直流/直流開關轉(zhuǎn)換器 1-3 Cell Step-Up DC/DC Converter RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率: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 安裝風格:SMD/SMT |
| MAX849ESE+ | 功能描述:直流/直流開關轉(zhuǎn)換器 1-3 Cell Step-Up DC/DC Converter RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率: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 安裝風格:SMD/SMT |
| MAX849ESE+T | 功能描述:直流/直流開關轉(zhuǎn)換器 1-3 Cell Step-Up DC/DC Converter RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率: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 安裝風格:SMD/SMT |
| MAX849ESE-T | 功能描述:直流/直流開關轉(zhuǎn)換器 1-3 Cell Step-Up DC/DC Converter RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率: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 安裝風格:SMD/SMT |
| MAX849EVKIT | 功能描述:直流/直流開關轉(zhuǎn)換器 1-Cell to 3-Cell High-Power Low-Noise Step-Up DC-DC Converter RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率: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 安裝風格:SMD/SMT |
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