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參數(shù)資料
| 型號(hào)： | L4947R |
| 廠商： | 意法半導(dǎo)體 |
| 英文描述： | 5V-0.5A VERY LOW DROP REGULATOR WITH RESET |
| 中文描述： | 5V的- 0.5A的非常低，復(fù)位降調(diào)節(jié) |
| 文件頁數(shù)： | 4/6頁 |
| 文件大小： | 57K |
| 代理商： | L4947R |
The current consumption of the device (quiescent
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. for L4947
and V
O
-0.3V typ. for L4947R value) the reset out-
Figure 1:
Typical Dropout Voltage vs. T
j
(I
o
= 500mA).
put instantaneously goes down (LOW status) in-
hibiting the microprocessor. The typical power 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
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 L4947/L4947Rspecially suitable for ap-
plicationsin 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.
Figure 2:
Reset Waveforms:
(1) WithoutExternal Capacitor C
d
.
(2) With ExternalCapacitorC
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 |
|---|---|
| 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 |
| L4949D | 功能描述:低壓差穩(wěn)壓器 - LDO 5V 100mA w/Power-On 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 |
| L4949DG | 功能描述:低壓差穩(wěn)壓器 - LDO 5V 100mA w/Power-On Reset 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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