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参数资料
| 型号： | MAX683EUA+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 7/12页 |
| 文件大小： | 0K |
| 描述： | IC REG SWITCHED CAP 5V .1A 8UMAX |
| 标准包装： | 2,500 |
| 类型： | 切换式电容器（充电泵） |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 5V |
| 输入电压： | 2.7 V ~ 5.5 V |
| 频率 - 开关： | 200kHz，1MHz |
| 电流 - 输出： | 100mA |
| 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-TSSOP，8-MSOP（0.118"，3.00mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-uMAX |
3.3V-Input to Regulated 5V-Output
Charge Pumps
IN
C X
S2
OUT
max) of supply current in this mode and the output pre-
sents a 50k ? impedance to ground. The device exits
shutdown once SHDN is forward biased (minimum of
1μA of current). The typical no-load shutdown exit time
is 50μs.
C IN
S1
OSC
When SHDN is pulled high through an external resistor
to V IN , the bias current into SHDN determines the
N-CHANNEL
Figure 4. Constant-Frequency-Mode Regulation
Table 1. Tradeoffs Between Operating
Modes
C OUT
charge-pump frequency. To select the frequency, cal-
culate the external resistor value, R EXT , using the fol-
lowing formula:
R EXT = 45000 (V IN - 0.69V) / f OSC
where R EXT is in k ? and f OSC is in kHz. Program the
frequency in the 50kHz to 2MHz range. This frequency
range corresponds to SHDN input currents between
1μA and 50μA. Proper operation of the oscillator is not
guaranteed beyond these limits. Currents lower than
1μA may shut down the device. The forward-biased
diode voltage from the SHDN input to GND has a tem-
perature coefficient of -2mV/°C.
FEATURE
Best Light-Load
Efficiency
Smallest External
Component Size
Output Ripple
Amplitude and
Frequency
Load Regulation
SKIP MODE
( SKIP = LOW)
Relatively large
amplitude, variable
frequency
Very Good
CONSTANT-
FREQUENCY MODE
( SKIP = HIGH)
Relatively small
amplitude, constant
frequency
Good
Undervoltage Lockout
The MAX682/MAX683/MAX684 have an undervoltage-
lockout feature that deactivates the devices when the
input voltage falls below 2.25V. Regulation at low input
voltages cannot be maintained. This safety feature
ensures that the device shuts down before the output
voltage falls out of regulation by a considerable amount
(typically 10% with no load). Once deactivated, hys-
teresis holds the device in shutdown until the input volt-
age rises 100mV above the lockout threshold.
Applications Information
output noise contains well-defined frequency compo-
nents, and the circuit requires much smaller external
capacitors for a given output ripple. However, constant-
frequency mode, due to higher operating current, is
less efficient at light loads than skip mode. Note: For
input voltages above 3.6V, the devices must operate in
constant-frequency mode. Table 1 summarizes the
tradeoffs between the two operating modes.
Frequency Selection and Shutdown
The SHDN pin on the MAX682/MAX683/MAX684 per-
forms a dual function: it shuts down the device and
determines the oscillator frequency. The SHDN input
looks like a diode to ground and should be driven
through a resistor.
Driving SHDN low places the device in shutdown
mode. This disables all switches, the oscillator, and
control logic. The device typically draws 0.1μA (5μA
Capacitor Selection
The MAX682/MAX683/MAX684 require only three exter-
nal capacitors (Figure 5). Their values are closely linked
to the output current capacity, oscillator frequency, out-
put noise content, and mode of operation.
Generally, the transfer capacitor (C X ) will be the small-
est, and the input capacitor (C IN ) is twice as large as
C X . Higher switching frequencies allow the use of
smaller C X and C IN . The output capacitor (C OUT ) can
be anywhere from 5-times to 50-times larger than C X ,
depending on the mode of operation and ripple toler-
ance. In continuous switching mode, smaller output rip-
ple allows smaller C OUT . In skip mode, a larger C OUT is
required to maintain low output ripple. Tables 2 and 3
show capacitor values recommended for lowest sup-
ply-current operation (skip mode) and smallest size oper-
ation (constant-frequency mode), respectively.
_______________________________________________________________________________________
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