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参数资料
| 型号： | MAX639CPA |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 11/13页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 5V/ADJ 225MA 8DIP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 50 |
| 类型： | 降压（降压） |
| 输出类型： | 两者兼有 |
| 输出数： | 1 |
| 输出电压： | 5V，1.3 V ~ 11.5 V |
| 输入电压： | 4 V ~ 11.5 V |
| 电流 - 输出： | 225mA |
| 同步整流器： | 无 |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 通孔 |
| 封装/外壳： | 8-DIP（0.300"，7.62mm） |
| 包装： | 管件 |
| 供应商设备封装： | 8-PDIP |
| 其它名称： | Q724982 |
5V/3.3V/3V/Adjustable, High-Efficiency,
Low I Q , Step-Down DC-DC Converters
160
V IN
C IN
100 μ F
6
V+
8
SHDN
LX
5
L = 100 μ H
140
120
T A = +25°C
L = 100 μ H
MAX639
100
MAX639
MAX640
MAX653 VOUT
1
1N5817
C OUT
100 μ F
80
60
40
GND
VFB
-5V
-3.3V
20
0
4
7
OR -3V
0
1
2
3
4
5
V+ (V)
Figure 6. Inverting Configuration
capacitor, even when the switch is off. This will usually not
be a problem for a 5V output at room temperature, since
the diode’s reverse leakage current and the feedback
resistors’ current typically drain the excess. However, if
the diode leakage is very low (which can occur at low
temperatures and/or small output voltages), charge may
build up on the output capacitor, making V OUT rise above
Figure 7. Maximum Current Capability of Figure 6 Circuit
87.0
86.5
86.0
its set point. If this happens, add a small load resistor
(typically 1M ? ) to the output to pull a few extra
microamps of current from the output capacitor.
Layout
Several of the external components in a MAX639/
MAX640/MAX653 circuit experience peak currents up
to 600mA. Wherever one of these components con-
nects to ground, there is a potential for ground bounce.
85.5
85.0
84.5
84.0
T A = +25°C
V OUT = -5V
L = 470 μ H
I OUT = 10mA
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
Ground bounce occurs when high currents flow
through the parasitic resistances of PC board traces.
What one component interprets as ground can differ
from the IC’s ground by several millivolts. This may
increase the MAX639/MAX640/MAX653’s output ripple,
since the error comparator (which is referenced to
ground) will generate extra switching pulses when they
are not needed. It is essential that the input filter capac-
itor ’s ground lead, the MAX639/MAX640/MAX653 ’s
GND pin, the diode ’s anode, and the output filter
capacitor’s ground lead are as close together as possi-
ble, preferably at the same point. Figure 5 shows a
suggested through-hole printed circuit layout that mini-
mizes ground bounce.
Inverter Configuration
Figure 6 shows the MAX639/MAX640/MAX653 in a
floating ground configuration. By tying what would nor-
mally be the output to the supply-voltage ground, the
IC’s GND pin is forced to a regulated -5V (MAX639),
V+ (V)
Figure 8. Efficiency of Figure 6 Circuit
-3.3V (MAX640), or -3V (MAX653). Avoid exceeding the
maximum differential voltage of 11.5V from V+ to V OUT .
Other negative voltages can be generated by placing a
voltage divider across C OUT and connecting the tap
point to VFB in the same manner as the normal step-
down configuration.
Two AA Batteries to 5V, 3.3V, or 3V
For battery-powered applications, where the signal
ground does not have to correspond to the power-supply
ground, the circuit in Figure 6 generates 5V (MAX639),
3.3V (MAX640), or 3V (MAX653) from a pair of AA batter-
ies. Connect the V IN ground point to your system’s input,
and connect the output to your system’s ground input.
This configuration has the added advantage of reduced
on resistance, since the IC’s internal power FET has V IN +
V OUT of gate drive (Figures 7 and 8).
______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX639CPA+ | 功能描述:直流/直流开关转换器 5/3.3/3V Adjustable Step-Down 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 |
| MAX639CSA | 功能描述:直流/直流开关转换器 5/3.3/3V Adjustable Step-Down 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 |
| MAX639CSA+ | 功能描述:直流/直流开关转换器 5/3.3/3V Adjustable Step-Down 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 |
| MAX639CSA+T | 功能描述:直流/直流开关转换器 5/3.3/3V Adjustable Step-Down 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 |
| MAX639CSA-T | 功能描述:直流/直流开关转换器 5/3.3/3V Adjustable Step-Down 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 |
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