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參數(shù)資料
| 型號： | LFC789D25-ADJ |
| 英文描述： | Dual Linear FET Controller |
| 中文描述： | 雙直線場效應管控制器 |
| 文件頁數(shù)： | 5/10頁 |
| 文件大小： | 145K |
| 代理商： | LFC789D25-ADJ |
LFC789D25-ADJ
DUAL LINEAR FET CONTROLLER
SLLS565
–
MARCH 2003
5
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
APPLICATION INFORMATION
FUNCTIONAL DESCRIPTION
A linear voltage regulator can be broken down into four essential building blocks: a pass transistor, a voltage
reference, a feedback network, and a control circuit to drive the pass element, based on the comparison
between the output voltage (as sampled by the feedback network) and the voltage reference. With the exception
of the pass transistor, the LFC789D25-ADJ provides the other three building blocks needed. Thus, with minimal
external components and low overall solution cost, a designer can create two independent, tightly regulated
output voltages capable of delivering high currents in excess of 3 A (as limited by the external pass transistor).
One output is fixed at 2.5 V. The other output can be adjusted to any desired voltage via an externally applied
signal to the V
REF
pin. Because the output of the regulator always tracks any changes to this V
REF
pin, it is
relatively easy to implement a tracking regulator. See the
typical application circuit
(Figure 1).
internal reference
The fixed 2.5-V output controller uses an internal temperature-compensated bandgap reference centered at
1.2 V. Its tolerance is designed to be
<±
2% over the specified temperature range, which, when coupled with the
low offset of the driver circuit, allows the 2.5-V output to have a tolerance of 2% over the specified temperature
range and full load.
external reference pin (V
REF
)
For the adjustable output controller, the V
REF
pin allows great flexibility for the designer. Taking a simple resistor
divider tied to an external voltage source and connecting the divider to the V
REF
pin allows the controller to
regulate an output voltage that is some fraction of the external voltage source. And, because any changes in
the external voltage source are sensed by the voltage divider, the regulated output tracks those changes.
If a tracking regulator is not desired, a fixed voltage can be achieved by applying a constant voltage to the V
REF
pin. This signal can be provided by a simple device such as the economical TL431 adjustable shunt regulator.
The V
REF
pin typically
sources
a current of 20 nA and, as such, has a minimal loading effect on the resistor
divider or the shunt regulator. The accuracy of the adjustable output depends on the accuracy of the signal
applied to the V
REF
pin. Using high-precision resistors or a TL431A (1% output tolerance) helps achieve good
accuracy.
feedback network (SENSE pins)
The 2.5-V controller senses the output voltage via the SEN_V
25
pin. This pin is tied to an internal resistor divider
that essentially halves the sensed output voltage and feeds it back to the controller for comparison to the internal
bandgap reference.
For the adjustable output controller, the SEN_V
ADJ
pin provides direct feedback of the output voltage to the
controller for comparison to the externally applied V
REF
signal.
controller/driver
Both drivers are essentially error amplifiers that can output a worst-case minimum of 9 V (10.5 V at 25
°
C) when
the LFC789D25-ADJ is powered by 12 V. This allows the controllers to regulate a large range of output
voltages, as limited by the threshold voltages of the external NMOS. Both drivers sample the output voltage via
a SEN pin. For the adjustable version, this SEN pin typically
sources
a current of 20 nA and, thus, has minimal
loading on the output voltage. For the 2.5-V version, this SEN pin
sinks
a current about 125
μ
A (including the
currents through the internal resistor divider); this results in minimal loading on the output voltage.
Although not tested, both of these controllers are designed with very low offset (typically less than 4 mV),
resulting in very accurate control of the drive signals.
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參數(shù)描述 |
|---|---|
| LFC789D25-ADJCDR | 制造商:Texas Instruments 功能描述:obsolete - ORDER LFC789D25CDR |
| LFC789D25CD | 功能描述:低壓差控制器 - LDO Dual Linear FET Controller RoHS:否 制造商:Micrel 最大輸入電壓:5.5 V 輸出電壓:Adjustable 輸出電流:10 mA 負載調(diào)節(jié): 輸出類型:Adjustable, Fixed 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:SOT-23-6 |
| LFC789D25CDE4 | 功能描述:低壓差控制器 - LDO Dual Linear FET Controller RoHS:否 制造商:Micrel 最大輸入電壓:5.5 V 輸出電壓:Adjustable 輸出電流:10 mA 負載調(diào)節(jié): 輸出類型:Adjustable, Fixed 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:SOT-23-6 |
| LFC789D25CDG4 | 功能描述:低壓差控制器 - LDO Dual Lin FET Cntrlr RoHS:否 制造商:Micrel 最大輸入電壓:5.5 V 輸出電壓:Adjustable 輸出電流:10 mA 負載調(diào)節(jié): 輸出類型:Adjustable, Fixed 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:SOT-23-6 |
| LFC789D25CDR | 功能描述:低壓差控制器 - LDO Dual Linear FET Controller RoHS:否 制造商:Micrel 最大輸入電壓:5.5 V 輸出電壓:Adjustable 輸出電流:10 mA 負載調(diào)節(jié): 輸出類型:Adjustable, Fixed 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:SOT-23-6 |
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