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参数资料
| 型号： | MAX639ESA+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 8/13页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 5V/ADJ 225MA 8SOIC |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 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： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-SOIC |
5V/3.3V/3V/Adjustable, High-Efficiency,
Low I Q , Step-Down DC-DC Converters
Figure 2 shows what happens to the ideal circuit of
Figure 1 if the switch turns on with a 66% duty cycle and
V+ = 3/2 V OUT . The inductor current rises more slowly
than it falls because the magnitude of the voltage
applied during t ON is less than that applied during t OFF .
Varying the duty cycle and switching frequency keeps
the peak current constant as input voltage varies. The
MAX639/MAX640/MAX653 control the switch (t ON and
t OFF ) according to the following equations:
Equation (1) t ON = 50μsV / (V+ - V OUT )
Equation (2) t OFF ≥ 50μsV / V OUT
Equation (3) I PEAK = 50μsV / L
These three equations ensure constant peak currents for
a given inductor value, across all input voltages (ignoring
the voltage drop across the diode (D1) and the resistive
losses in the switch and inductor). The variable duty
cycle also ensures that the current through the inductor
discharges to zero at the end of each pulse.
Figure 3 shows the MAX639/MAX640/MAX653 block dia-
gram and a typical connection in which 9V is converted
to 5V (MAX639), 3.3V (MAX640), or 3.0V (MAX653). The
sequence of events in this application is as follows:
INPUT, +5.5V TO +11.5V (MAX639),
+3.8V TO +11.5V (MAX640), +3.5V TO +11.5V (MAX653)
When the output dips:
(1) The error comparator switches high.
(2) The internal oscillator starts (15μs start-up time)
and connects to the gate of the LX output driver.
(3) LX turns on and off according to t ON and t OFF ,
charging and discharging the inductor, and sup-
plying current to the output (as described above).
When the output voltage recovers:
(1) The comparator switches low.
(2) LX turns off.
(3) The oscillator shuts down to save power.
Fixed or Adjustable Output
For operation at the preset output voltage, connect VFB
to GND; no external resistors are required. For other
output voltages, use an external voltage divider. Set the
output voltage using R3 and R4 as determined by the
following formula:
R3 = R4 [(V OUT / VFB Threshold) - 1]
where R4 is any resistance in the 10k ? to 1M ? range (typ-
ically 100k ? ), and the VFB threshold is typically 1.28V.
8
6
5V, 3.3V OR 3.0V
C IN
33 μ F
SHDN
V+
LX
5
L = 100 μ H
AT 100mA
+1.28V
BANDGAP
REFERENCE
ERROR
VARIABLE
FREQUENCY
AND
1N5817
COMPARATOR
DUTY-CYCLE
OSCILLATOR
VOUT 1
R1
3 LBI
2 LBO
R2
Figure 3. Block Diagram
LOW-BATTERY
COMPARATOR
VFB
7
MODE-SELECT
COMPARATOR
50mV
GND
4
C OUT
100 μ F
MAX639
MAX640
MAX653
8
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX639EVKIT-DIP | 制造商:Maxim Integrated Products 功能描述:5V/ADJUSTABLE, HIGH-EFFICIENCY, LOW I Q, STEP - Bulk |
| MAX639MJA | 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 |
| MAX63XXSUPEVKIT | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Evaluation Kit for the MAX3762[MAX3762EVKIT ] |
| MAX6400BS22 | 制造商:Maxim Integrated Products 功能描述:UP SUPERVISORY CIRCUIT IN 4-BUMP 2X2 CHIP-SCA - Bulk |
| MAX6400BS22+ | 制造商:Maxim Integrated Products 功能描述:PROCESSOR SUPERVISOR 2.2V 1UA 4UCSP - Rail/Tube |
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