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參數資料
| 型號： | L4947PD |
| 廠商： | 意法半導體 |
| 英文描述： | 5V-0.5A Very Low Drop Regulator with Reset(帶復位低壓差穩(wěn)壓器) |
| 中文描述： | 5V的- 0.5A的非常低壓降穩(wěn)壓器具有復位（帶復位低壓差穩(wěn)壓器） |
| 文件頁數： | 4/6頁 |
| 文件大?。?/td> | 62K |
| 代理商： | L4947PD |
current) is maximum 13mA - over full T - when no
load currentis required.
The internal antisaturation circuit allows a drastic
reduction in the current peak which takes place
during the start up.
The reset functionsupervises the regulator output
voltage inhibiting the microprocessor when the
device is out of regulation and resetting it at the
power-on after a settabledelay. The reset is LOW
when the output voltage value is lower than the
reset threshold voltage. At the power-on phase
the output voltage increases (see Fig. 2) and -
when it reaches the power-on V
O
threshold V
RT
(On) - the reset output becomes HIGH after a de-
lay time set by the external capacitor C
d
. At the
power-off the output voltage decreases : at the
V
RT(Off)
threshold value (V
O
-0.15V typ. value) the
reset output instantaneously goes down (LOW
status) inhibiting the microprocessor. The typical
Figure 1:
Typical Dropout Voltage vs. T
j
(I
o
= 500mA).
power on-off hysteresis is 50mV.
The three gain stages (operational amplifier,
driver and power PNP) require the external ca-
pacitor (C
omin
= 20
μ
F) to guarantee the global
stabilityof the system.
Load dump and field decay protections (
±
80V),
reverse voltage (– 18V) and short circuit protec-
tion, thermal shutdown are the main features that
make the L4947PD specially suitable for applica-
tions in the automotive enviroment.
EXTERNAL COMPENSATION
Since the purpose of a voltageregulatoris to sup-
ply and load variations, the open loop gain of the
regulator must be very high at low frequencies.
This may cause instability as a result of the vari-
ous poles present in the loop. To avoid this insta-
bility dominant pole compensation is used to re-
duce phase shift due to other poles at the unity
gain frequency. The lower the frequency of these
others poles at the unity gain frequency. The
lower the frequency of these other poles, the
greater must be capacitor esed to create the
dominant pole for the same DC gain.
Where the output transistor is a lateral PNP type
there is a pole in the regulation loop at a fre-
quencybtoo low to be compensated by a capaci-
tor which can be integrated. An external compen-
sation is thereforenecessary so a very high value
capacitor must be connected from the output to
ground.
The paeassitic equivalent series resistance of the
capacitor used adds a zero to the regulationloop.
This zero may compromise the stability of the
system since its effect tends to cancel the effect
of the pole added. In regulatorsthis ESR must be
less than 3
and the minimum capacitor value is
47
μ
F.
Vrpeak
Vrthys
V
O
V
RT(on)
V
RT(off
)
(1)
(2)
V
dthh
V
dthl
V
R
V
D
Td
(2)
Vdisch
Vrsat
D94AT109
Figure 2:
Reset Waveforms:
(1) WithoutExternal Capacitor C
d
.
(2) With ExternalCapacitorC
d
.
L4947PD
4/6
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相關代理商/技術參數 |
參數描述 |
|---|---|
| L4947PD013TR | 功能描述:低壓差穩(wěn)壓器 - LDO 5.0V 0.5A Positive RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動電壓（最大值）:307 mV 輸出電流:1 A 負載調節(jié):0.3 % 輸出端數量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| L4947R | 功能描述:低壓差穩(wěn)壓器 - LDO 5.0V 0.5A Positive RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動電壓（最大值）:307 mV 輸出電流:1 A 負載調節(jié):0.3 % 輸出端數量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| L4948 | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:QUAD VOLTAGE REGULATOR WITH INHIBIT AND RESET |
| L4949 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:AC-DC Offline Switching Controllers/Regulators |
| L4949_06 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:100 mA, 5.0 V, Low Dropout Voltage Regulator with Power−On Reset |
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