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参数资料
| 型号： | MAX1806EUA08 |
| 厂商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分类： | 基准电压源/电流源 |
| 英文描述： | 3A Fixed Low Dropout Linear Regulator (LDO) |
| 中文描述： | FIXED/ADJUSTABLE POSITIVE LDO REGULATOR, PDSO8 |
| 封装： | POWER, MICRO MAX PACKAGE-8 |
| 文件页数： | 7/10页 |
| 文件大小： | 263K |
| 代理商： | MAX1806EUA08 |
M
500mA, Low-Voltage Linear Regulator in μMAX
_______________________________________________________________________________________
7
Detailed Description
The MAX1806 is a low-dropout, low-quiescent-current
linear regulator. The device supplies loads up to
500mA and is available with preset output voltages. As
illustrated in Figure 1, the MAX1806 includes a 0.8V ref-
erence, error amplifier, P-channel pass transistor, and
internal feedback voltage-divider.
The reference is connected to the error amplifier, which
compares it with the feedback voltage and amplifies
the difference. If the feedback voltage is lower than the
reference voltage, the pass-transistor gate is pulled
lower, which allows more current to pass to the output
increasing the output voltage. If the feedback voltage is
too high, the pass-transistor gate is pulled up, allowing
less current to pass to the output.
The output voltage is fed back through either an inter-
nal resistive voltage-divider connected to OUT or an
external resistor network connected to SET. The dual-
mode comparator examines V
SET
and selects the feed-
back path. If V
SET
is below 35mV, the internal feedback
path is used, and the output is regulated to the factory-
preset voltage. Additional blocks include an output cur-
rent limiter, thermal sensor, and shutdown logic.
Internal P-Channel Pass Transistor
The MAX1806 features a 0.4
P-channel MOSFET pass
transistor. Unlike similar designs using PNP pass tran-
sistors, P-channel MOSFETs require no base drive,
which reduces operating current. PNP-based regula-
tors also waste considerable current in dropout when
the pass transistor saturates, and use high base-drive
currents under large loads. The MAX1806 does not suf-
fer from these problems.
Output Voltage Selection
The MAX1806
’
s dual-mode operation allows operation
in either a preset voltage mode or an adjustable mode.
Connect SET to GND to select the preset output volt-
age. The two-digit part number suffix identifies the out-
put voltage (see
Selector Guide
). For example, the
MAX1806EUA33 has a preset 3.3V output voltage. The
output voltage may also be adjusted by connecting a
voltage-divider from OUT to SET (Figure 2). Select R2 in
the 25k
to 100k
range. Calculate R1 with the follow-
ing equation:
R1 = R2 [(V
OUT
/ V
SET
) - 1]
where V
SET
= 0.8V, and V
OUT
may range from 0.8V
to 4.5V.
Shutdown
Drive
SHDN
low to enter shutdown. During shutdown,
the output is disconnected from the input, and supply
current drops to 0.02μA. When in shutdown, POK pulls
low. The capacitance and load at OUT determine the
rate at which V
OUT
decays.
SHDN
can be pulled as
high as +6V, regardless of the input and output voltage.
Power-OK Output
The POK output pulls low when OUT is less than 93% of
the nominal regulation voltage. Once OUT exceeds
93% of the nominal voltage, POK goes high imped-
ance. POK is an open-drain N-channel output. To
obtain a logic voltage output, connect a pullup resistor
from POK to OUT. A 100k
resistor works well for most
applications. POK can be used to signal a microcon-
troller (μC), or drive an external LED to indicate power
failure. When the MAX1806 is shutdown, POK is held
low independent of the output voltage. If unused, leave
POK grounded or unconnected.
Current Limit
The MAX1806 monitors and controls the pass transis-
tor
’
s gate voltage, limiting the output current to 1.4A
(typ). The output can be shorted to ground for an indefi-
nite period of time without damaging the part.
Thermal Overload Protection
Thermal overload protection limits total power dissipa-
tion in the MAX1806. When the junction temperature
exceeds T
J
= +170
°
C, a thermal sensor turns off the
pass transistor, allowing the device to cool. The thermal
sensor turns the pass transistor on again after the junc-
tion temperature cools by 20
°
C, resulting in a pulsed
output during continuous thermal overload conditions.
Thermal overload protection protects the MAX1806 in
the event of fault conditions. For continuous operation,
do not exceed the absolute maximum junction-temper-
ature rating of T
J
= +150
°
C.
Operating Region and Power Dissipation
The MAX1806
’
s maximum power dissipation depends
on the thermal resistance of the IC package and circuit
board, the temperature difference between the die
junction and ambient air, and the rate of air flow. The
power dissipated in the device is P = I
OUT
(V
IN
-
V
OUT
). The maximum allowed power dissipation is
1.3W or:
PMAX = (T
J(MAX)
- T
A
) / (
θ
JC
+
θ
CA
)
where T
J
- T
A
is the temperature difference between the
MAX1806 die junction and the surrounding air,
θ
JC
is
the thermal resistance from the junction to the case,
and
θ
CA
is the thermal resistance from the case
through the PC board, copper traces, and other materi-
als to the surrounding air. The MAX1806 package fea-
tures an exposed thermal pad on its underside. This
pad lowers the package
’
s thermal resistance by provid-
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1806EUA08+ | 功能描述:低压差稳压器 - LDO 500mA RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| MAX1806EUA08+T | 功能描述:低压差稳压器 - LDO 500mA RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| MAX1806EUA08+TG48 | 制造商:Maxim Integrated Products 功能描述:- Tape and Reel |
| MAX1806EUA08-T | 功能描述:低压差稳压器 - LDO 500mA RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| MAX1806EUA08-TG075 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
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