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參數(shù)資料
| 型號(hào)： | L4947 |
| 廠商： | 意法半導(dǎo)體 |
| 元件分類： | 基準(zhǔn)電壓源/電流源 |
| 英文描述： | Very Low Drop Voltage Regulator with Reset(帶復(fù)位的低壓差穩(wěn)壓器) |
| 中文描述： | 非常低壓降穩(wěn)壓器具有復(fù)位（帶復(fù)位的低壓差穩(wěn)壓器） |
| 文件頁(yè)數(shù)： | 4/6頁(yè) |
| 文件大?。?/td> | 84K |
| 代理商： | L4947 |
The current consumption of the device (quiescent
current) is maximum 13mA - over full T - when no
load current is required.
The internal antisaturation circuit allows a drastic
reduction in the current peak which takes place
duringthe startup.
The reset function supervisesthe regulatoroutput
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 becomesHIGH 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. for L4947
and V
O
-0.3V typ. for L4947R value) the reset out-
Figure1:
Typical Dropout Voltage vs. T
j
(I
o
= 500mA).
put instantaneously goes down (LOW status) in-
hibitingthe microprocessor. The typicalpower on-
off hysteresisis 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
stability of 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 L4947/L4947Rspecially suitable for ap-
plicationsin the automotive enviroment.
EXTERNAL COMPENSATION
Since the purpose of a voltageregulator is 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
dominantpole 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 veryhigh value
capacitor must be connected from the output to
ground.
The paeassitic equivalent series resistance of the
capacitor used adds a zero to the regulation loop.
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.
Figure2:
Reset Waveforms:
(1) WithoutExternalCapacitor C
d
.
(2) WithExternal Capacitor C
d
.
L4947 - L4947R
4/6
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| L4947H | 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(dòng)電壓（最大值）:307 mV 輸出電流:1 A 負(fù)載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| L4947L | 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(dòng)電壓（最大值）:307 mV 輸出電流:1 A 負(fù)載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| L4947PD | 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(dòng)電壓（最大值）:307 mV 輸出電流:1 A 負(fù)載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| 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(dòng)電壓（最大值）:307 mV 輸出電流:1 A 負(fù)載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)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(dòng)電壓（最大值）:307 mV 輸出電流:1 A 負(fù)載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
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