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参数资料
| 型号： | DS21Q554 |
| 厂商： | DALLAS SEMICONDUCTOR |
| 元件分类： | Digital Transmission Interface |
| 英文描述： | DATACOM, PCM TRANSCEIVER, PBGA256 |
| 封装： | MCM, BGA-256 |
| 文件页数： | 5/7页 |
| 文件大小： | 174K |
| 代理商： | DS21Q554 |
MAX1595
Regulated 3.3V/5.0V Step-Up/Step-Down
Charge Pump
_______________________________________________________________________________________
5
Applications Information
Using white LEDs to backlight LCDs is an increasingly
popular approach for portable information devices
(Figure 2). Because the forward voltage of white LEDs
exceeds the available battery voltage, the use of a
charge pump such as the MAX1595 provides high effi-
ciency, small size, and constant light output with chang-
ing battery voltages. If the output is used only to light
LEDs, the output capacitor can be greatly reduced. The
frequency modulation of the LED intensity is not dis-
cernible to the human eye, and the smaller capacitor
saves both size and cost.
Adding two Schottky diodes and two capacitors imple-
ments a tripler and allows the MAX1595_ _ _50 to regu-
late a current of 75mA with a supply voltage as low as
2.3V (Figure 3).
Capacitor Selection
The MAX1595 requires only three external capacitors
(Figure 4). Their values are closely linked to the output
current capacity, oscillator frequency, output noise con-
tent, and mode of operation.
Generally, the transfer capacitor (CX) will be the smallest,
and the input capacitor (CIN) is twice as large as CX.
Higher switching frequencies allow the use of the smaller
CX and CIN. The output capacitor (COUT) can be any-
where from 5-times to 50-times larger than CX. Table 1
shows recommended capacitor values.
In addition, the following equation approximates output
ripple:
VRIPPLE
IOUT / (2 x fOSC x COUT)
Table 2 lists the manufacturers of recommended capaci-
tors. Ceramic capacitors will provide the lowest ripple
due to their typically lower ESR.
Power Dissipation
The power dissipated in the MAX1595 depends on out-
put current and is accurately described by:
PDISS = IOUT (2VIN - VOUT)
PDISS must be less than that allowed by the package
rating.
Layout Considerations
All capacitors should be soldered in close proximity to
the IC. Connect ground and power ground through a
short, low-impedance trace. The input supply trace
should be as short as possible. Otherwise, an additional
input supply filter capacitor (tantalum or electrolytic) may
be required.
AOUT
IN
INPUT
2.3V
1
F
SHDN
GND
PGND
OUT
MAX1595_ _ _50
0.22
F
CXP
CXN
1
F
OUTPUT
REGULATED 5V
75mA
1
F
0.22
F
OUT
IN
VIN
COUT =
0.47
F
CIN = 1
F
CX = 0.1
F
SHDN
GND
CXP
CXN
PGND
AOUT
MAX1595_ _ _50
100
100
100
Figure 3. Regulated Voltage Tripler
Figure 2. White LED Bias Supply
CX
0.22
F
CIN
1
F
COUT
1
F
OUT
CXN
CXP
SHDN
IN
OUT
7
4
6
3
2
8
ON
OFF
GND
5
PGND
AOUT
1
MAX1595
IN
Figure 4. Standard Operating Circuit
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相关代理商/技术参数 |
参数描述 |
|---|---|
| DS21Q554B | 功能描述:网络控制器与处理器 IC Quad E1 Transceiver RoHS:否 制造商:Micrel 产品:Controller Area Network (CAN) 收发器数量: 数据速率: 电源电流（最大值）:595 mA 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:PBGA-400 封装:Tray |
| DS21Q554B+ | 功能描述:网络控制器与处理器 IC Quad E1 Transceiver RoHS:否 制造商:Micrel 产品:Controller Area Network (CAN) 收发器数量: 数据速率: 电源电流（最大值）:595 mA 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:PBGA-400 封装:Tray |
| DS21Q554BN | 功能描述:网络控制器与处理器 IC RoHS:否 制造商:Micrel 产品:Controller Area Network (CAN) 收发器数量: 数据速率: 电源电流（最大值）:595 mA 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:PBGA-400 封装:Tray |
| DS21Q554BN+ | 功能描述:网络控制器与处理器 IC Quad E1 Transceiver RoHS:否 制造商:Micrel 产品:Controller Area Network (CAN) 收发器数量: 数据速率: 电源电流（最大值）:595 mA 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:PBGA-400 封装:Tray |
| DS21Q554BW | 功能描述:网络控制器与处理器 IC RoHS:否 制造商:Micrel 产品:Controller Area Network (CAN) 收发器数量: 数据速率: 电源电流（最大值）:595 mA 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:PBGA-400 封装:Tray |
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