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參數資料
| 型號： | ADM666A* |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | 基準電壓源/電流源 |
| 英文描述： | Tri-Mode: +3.3 V. +5 V. Adjustable Micropower Linear Voltage Regulators |
| 中文描述： | 三模式：3.3伏5五，調節微功率線性穩壓器 |
| 文件頁數： | 5/9頁 |
| 文件大小： | 331K |
ADM663A/ADM666A
REV. 0
–5–
the current drain to a low quiescent (9
μ
A maximum) current.
This is very useful for low power applications. The SHDN input
should be driven with a CMOS logic level signal since the input
threshold is 0.3 V. In TTL systems, an open collector driver
with a pull-up resistor may be used.
If the shutdown function is not being used, then it should be
connected to GND.
Low Supply or Low Battery Detection
The ADM666A contains on-chip circuitry for low power supply
or battery detection. If the voltage on the LBI pin falls below the
internal 1.3 V reference, then the open drain output LBO will
go low. The low threshold voltage may be set to any voltage
above 1.3 V by appropriate resistor divider selection.
R
3
=
R
4
V
BATT
1.3
V
1
where R3 and R4 are the resistive divider resistors and V
BATT
is
the desired low voltage threshold.
Since the LBI input leakage current is less than 10 nA, large val-
ues may be selected for R3 and R4 in order to minimize loading.
For example, a 6 V low threshold may be set using 10 M
for
R3 and 2.7 M
for R4.
ADM666A
SENSE
V
OUT
GND
V
IN
V
SET
LBI
+1.3V TO +15V
OUTPUT
+2V TO +16V
INPUT
R
CL
R2
R1
LBO
SHDN
R3
R4
LOW
BATTERY
OUTPUT
Figure 6. ADM666A Adjustable Output with Low Battery
Detection
High Current Operation
The ADM663A contains an additional output, V
OUT1
, suitable
for directly driving the base of an external NPN transistor. Fig-
ure 7 shows a configuration which can be used to provide +5 V
with boosted current drive. A 1
current sensing resistor limits
the current at 0.5 A.
ADM663A
V
OUT1
V
OUT2
GND
V
IN
SHDN
2N4237
V
IN
100
1.0
SENSE
V
SET
+
10
μ
F
+
10
μ
F
SHUTDOWN
+5V, 0.5A
OUTPUT
Figure 7. ADM663A Boosted Output Current (0.5 A)
The resistor values may be selected by first choosing a value for
R1 and then selecting R2 according to the following equation:
R
2
=
R
1
×
V
OUT
1.30
1
The input leakage current on V
SET
is 10 nA maximum. This al-
lows large resistor values to be chosen for R1 and R2 with little
degradation in accuracy. For example, a 1 M
resistor may be
selected for R1, and then R2 may be calculated accordingly.
The tolerance on V
SET
is guaranteed at less than
±
30 mV so in
most applications, fixed resistors will be suitable.
ADM663A
ADM666A
SENSE
V
OUT(2)
GND
V
IN
V
SET
SHDN
+1.3V TO +15V
OUTPUT
+2V TO +16V
INPUT
R
CL
R2
R1
Figure 5. Adjustable Output
Current Limiting
Current limiting may be achieved by using an external current
sense resistor in series with V
OUT(2)
. When the voltage across
the sense resistor exceeds the internal 0.5 V threshold, current
limiting is activated. The sense resistor is therefore chosen such
that the voltage across it will be 0.5 V when the desired current
limit is reached.
R
CL
=
0.5
I
CL
where R
CL
is the current sense resistor, I
CL
is the maximum
current limit.
The value chosen for R
CL
should also ensure that the current is
limited to less than the 100 mA absolute maximum rating and
also that the power dissipation will also be within the package
maximum ratings.
If current limiting is employed, there will be an additional volt-
age drop across the sense resistor that must be considered when
determining the regulators dropout voltage.
If current limiting is not used, the SENSE input should be con-
nected to V
OUT(2)
.
Shutdown Input (SHDN)
The SHDN input allows the regulator to be turned off with a
logic level signal. This will disable the output and reduce
Table I. Output Voltage Selection
V
SET
V
OUT
GND
V
IN
R1/R2
+5 V
+3 V
ADJ
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相關代理商/技術參數 |
參數描述 |
|---|---|
| ADM666AAN | 制造商:AD 制造商全稱:Analog Devices 功能描述:Tri-Mode: +3.3 V, +5 V, Adjustable Micropower Linear Voltage Regulators |
| ADM666AAR | 制造商:AD 制造商全稱:Analog Devices 功能描述:Tri-Mode: +3.3 V, +5 V, Adjustable Micropower Linear Voltage Regulators |
| ADM666AN | 制造商:Analog Devices 功能描述:Standard Regulator Pos 1.3V to 16V5V 0.04A 8-Pin PDIP 制造商:Analog Devices 功能描述:IC V REG ADJ +2/16.5V DIP8 666 |
| ADM666AR | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Tri-Mode: +3.3 V +5 V Adjustable Micropower Linear Voltage Regulators(332.03 k) |
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