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參數(shù)資料
| 型號： | ADP3334 |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | 基準(zhǔn)電壓源/電流源 |
| 英文描述： | Cap-Free, NMOS, 150mA Low Dropout Regulator with Reverse Current Protection |
| 中文描述： | 無電容，NMOS管，150mA的低壓差穩(wěn)壓器的反向電流保護(hù) |
| 文件頁數(shù)： | 6/8頁 |
| 文件大?。?/td> | 230K |
| 代理商： | ADP3334 |
REV. 0
ADP3334
–6–
T HE ORY OF OPE RAT ION
T he new anyCAP
LDO ADP3334 uses a single control loop for
regulation and reference functions. T he output voltage is sensed
by a resistive voltage divider consisting of R1 and R2 which is
varied to provide the available output voltage option. Feedback
is taken from this network by way of a series diode (D1) and a
second resistor divider (R3 and R4) to the input of an amplifier.
PTAT
V
OS
NONINVERTING
WIDEBAND
DRIVER
INPUT
Q1
ADP3334
COMPENSATION
CAPACITOR
ATTENUATION
(V
BANDGAP
/V
OUT
)
R1
D1
R2
R3
R4
OUTPUT
PTAT
CURRENT
(a)
C
LOAD
R
LOAD
FB
GND
g
m
Figure 2. Functional Block Diagram
A very high gain error amplifier is used to control this loop. T he
amplifier is constructed in such a way that equilibrium pro-
duces a large, temperature-proportional input, “offset voltage”
that is repeatable and very well controlled. T he temperature-
proportional offset voltage is combined with the complementary
diode voltage to form a “virtual bandgap” voltage, implicit in
the network, although it never appears explicitly in the circuit.
Ultimately, this patented design makes it possible to control
the loop with only one amplifier. T his technique also improves
the noise characteristics of the amplifier by providing more
flexibility on the trade-off of noise sources that leads to a low
noise design.
T he R1, R2 divider is chosen in the same ratio as the bandgap
voltage to the output voltage. Although the R1, R2 resistor divider
is loaded by the diode D1 and a second divider consisting of R3
and R4, the values can be chosen to produce a temperature stable
output. T his unique arrangement specifically corrects for the
loading of the divider thus avoiding the error resulting from
base current loading in conventional circuits.
T he patented amplifier controls a new and unique noninverting
driver that drives the pass transistor, Q1. T he use of this special
noninverting driver enables the frequency compensation to
include the load capacitor in a pole-splitting arrangement to
achieve reduced sensitivity to the value, type, and ESR of the
load capacitance.
Most LDOs place very strict requirements on the range of ESR
values for the output capacitor because they are difficult to stabilize
due to the uncertainty of load capacitance and resistance. More-
over, the ESR value, required to keep conventional LDOs stable,
changes depending on load and temperature. T hese ESR limita-
tions make designing with LDOs more difficult because of their
unclear specifications and extreme variations over temperature.
With the ADP3334 anyCAP LDO, this is no longer true. It can
be used with virtually any good quality capacitor, with no con-
straint on the minimum ESR. T his innovative design allows the
circuit to be stable with just a small 1
μ
F capacitor on the out-
put. Additional advantages of the pole-splitting scheme include
superior line noise rejection and very high regulator gain, which
leads to excellent line and load regulation. An impressive
±
1.8%
accuracy is guaranteed over line, load, and temperature.
Additional features of the circuit include current limit and ther-
mal shutdown.
APPL IC AT ION INF ORMAT ION
Capacitor Selection
Output Capacitors: as with any micropower device, output
transient response is a function of the output capacitance. T he
ADP3334 is stable with a wide range of capacitor values, types
and ESR (anyCAP). A capacitor as low as 1
μ
F is all that is
needed for stability; larger capacitors can be used if high output
current surges are anticipated. T he ADP3334 is stable with
extremely low ESR capacitors (ESR
ceramic capacitors (MLCC) or OSCON. Note that the effective
capacitance of some capacitor types may fall below the mini-
mum over temperature or with DC voltage.
0), such as multilayer
Input Bypass Capacitor
An input bypass capacitor is not strictly required but is advisable
in any application involving long input wires or high source
impedance. Connecting a 1
μ
F capacitor from IN to ground
reduces the circuit’s sensitivity to PC board layout. If a larger
value output capacitor is used, then a larger value input capaci-
tor is also recommended.
Noise Reduction
A noise reduction capacitor (C
NR
) can be placed between the
output and the feedback pin to further reduce the noise by
6 dB–10 dB (T PC 18). Low leakage capacitors in 100 pF to
1 nF range provide the best performance. Since the feedback
pin (FB) is internally connected to a high impedance node, any
connection to this node should be carefully done to avoid noise
pickup from external sources. T he pad connected to this pin
should be as small as possible and long PC board traces are not
recommended.
When adding a noise reduction capacitor, maintain a mini-
mum load current of 1 mA when not in shutdown.
It is important to note that as C
NR
increases, the turn-on time
will be delayed. With C
NR
values of 1 nF, this delay may be
on the order of several milliseconds.
C
NR
ADP3334
OUT
V
IN
IN
GND
V
OUT
ON
OFF
IN
OUT
R1
R2
SD
C
IN
1 F
FB
C
OUT
1 F
Figure 3. Typical Application Circuit
Output Voltage
T he ADP3334 has an adjustable output voltage that can be set
by an external resistor divider. T he output voltage will be divided
by R1 and R2, and then fed back to the FB pin.
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PDF描述 |
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| ADP3335ARM-18 | Cap-Free, NMOS, 150mA Low Dropout Regulator with Reverse Current Protection |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADP3334ACP | 制造商:AD 制造商全稱:Analog Devices 功能描述:High Accuracy, Low IQ, anyCAP Adjustable Low Dropout Regulator |
| ADP3334ACP-REEL7 | 制造商:Analog Devices 功能描述:LDO Regulator Pos 1.5V to 10V 0.8A 8-Pin LFCSP EP T/R |
| ADP3334ACPZ-REEL7 | 功能描述:IC REG LDO ADJ .5A 8LFCSP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 系列:anyCAP® 標(biāo)準(zhǔn)包裝:75 系列:- 穩(wěn)壓器拓?fù)浣Y(jié)構(gòu):正，可調(diào)式 輸出電壓:1.2 V ~ 37 V 輸入電壓:4.2 V ~ 40 V 電壓 - 壓降（標(biāo)準(zhǔn)）:- 穩(wěn)壓器數(shù)量:1 電流 - 輸出:500mA 電流 - 限制（最?。?500mA 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:TO-252-3，DPak（2 引線+接片），SC-63 供應(yīng)商設(shè)備封裝:TO-252-3 包裝:管件 產(chǎn)品目錄頁面:1286 (CN2011-ZH PDF) 其它名稱:*LM317AMDT/NOPBLM317AMDT |
| ADP3334ACPZ-REEL7 | 制造商:Analog Devices 功能描述:LDO, ADJ, 1.5V TO 10V, 500mA, LFCSP-8 |
| ADP3334AR | 制造商:Rochester Electronics LLC 功能描述:500 MA ADJUSTABLE ANYCAP LDO - Bulk 制造商:Analog Devices 功能描述:IC VOLTAGE REGULATOR |
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