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參數(shù)資料
| 型號(hào)： | LX8117-28CST |
| 廠商： | MICROSEMI CORP-ANALOG MIXED SIGNAL GROUP |
| 元件分類： | 基準(zhǔn)電壓源/電流源 |
| 英文描述： | 0.8, 1 & 1.2A LOW DROPOUT POSITIVE REGULATORS |
| 中文描述： | 2.85 V FIXED POSITIVE LDO REGULATOR, 1.2 V DROPOUT, PDSO4 |
| 封裝： | PLASTIC, SOT-223, 3 PIN |
| 文件頁(yè)數(shù)： | 7/9頁(yè) |
| 文件大?。?/td> | 222K |
| 代理商： | LX8117-28CST |
0.8, 1 & 1.2A L
OW
D
ROPOUT
P
OSITIVE
R
EGULATORS
LX8117-xx/8117A-xx/8117B-xx
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
7
Copyright 1999
Rev. 1.4 3/99
P
R O D U C T I O N
D
A T A
S
H E E T
A P P L I C AT I O N N O T E S
FIGURE 2
— BASIC ADJUSTABLE REGULATOR
R2+R1
R1
LX8117-xx
OUT
IN
ADJ
V
OUT
V
IN
R1
R2
V
REF
I
ADJ
50μA
V
OUT
= V
REF
1 + R2
ADJ
R2
R1
OVERLOAD RECOVERY
(continued)
If this limited current is not sufficient to develop the designed
voltage across the output resistor, the voltage will stabilize at some
lower value, and will
never
reach the designed value. Under these
circumstances, it may be necessary to cycle the input voltage down
to zero in order to make the regulator output voltage return to
regulation.
RIPPLE REJECTION
Ripple rejection can be improved by connecting a capacitor
between the ADJ pin and ground. The value of the capacitor should
be chosen so that the impedance of the capacitor is equal in
magnitude to the resistance of R1
at the ripple frequency
. The
capacitor value can be determined by using this equation:
C = 1 / (6.28 * F
R
* R1)
where: C
≡
the value of the capacitor in Farads;
select an equal or larger standard value.
≡
the ripple frequency in Hz
≡
the value of resistor R1 in ohms
F
R
R1
At a ripple frequency of 120Hz, with R1 = 100
:
C = 1 / (6.28 * 120Hz * 100
) = 13.3μF
The closest equal or larger standard value should be used, in this
case, 15μF.
When an ADJ pin bypass capacitor is used, output ripple
amplitude will be essentially independent of the output voltage. If
an ADJ pin bypass capacitor is not used, output ripple will be
proportional to the ratio of the output voltage to the reference
voltage:
M = V
OUT
/V
REF
where: M
≡
a multiplier for the ripple seen when the
ADJ pin is optimally bypassed.
V
REF
= 1.25V.
For example, if V
OUT
= 2.5V the output ripple will be:
M = 2.5V/1.25V= 2
Output ripple will be twice as bad as it would be if the ADJ pin
were to be bypassed to ground with a properly selected capacitor.
OUTPUT VOLTAGE
The LX8117 ICs develop a 1.25V reference voltage between the output
and the adjust terminal (See Figure 2). By placing a resistor, R1,
between these two terminals, a constant current is caused to flow
through R1 and down through R2 to set the overall output voltage.
Normally this current is the specified minimum load current of 10mA.
Because I
is very small and constant when compared with the current
through R1, it represents a small error and can usually be ignored.
LOAD REGULATION
Because the LX8117 regulators are three-terminal devices, it is not
possible to provide true remote load sensing. Load regulation will
be limited by the resistance of the wire connecting the regulator to
the load. The data sheet specification for load regulation is
measured at the bottom of the package. Negative side sensing is a
true Kelvin connection, with the bottom of the output divider
returned to the negative side of the load. Although it may not be
immediately obvious, best load regulation is obtained when the top
of the resistor divider, (R1), is connected
directly
to the case of the
regulator,
not to the load
. This is illustrated in Figure 3. If R1 were
connected to the load, the effective resistance between the regulator
and the load would be:
R
Peff
= R
P
*
where: R
P
≡
Actual parasitic line resistance.
When the circuit is connected as shown in Figure 3, the parasitic
resistance appears as its actual value, rather than the higher R
Peff
.
LX8117-xx
OUT
IN
ADJ
V
IN
R1
R2
R
L
R
Parasitic
Line Resistance
Connect
R1 to Case
of Regulator
Connect
R2
to Load
FIGURE 3
— CONNECTIONS FOR BEST LOAD REGULATION
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LX8117-28CSTT | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:Positive Fixed Voltage Regulator |
| LX8117-33 | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:0.8, 1 & 1.2A LOW DROPOUT POSITIVE REGULATORS |
| LX8117-33CDD | 功能描述:IC REG LDO 3.3V TO263 RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 穩(wěn)壓器拓?fù)浣Y(jié)構(gòu):正，固定式 輸出電壓:3V 輸入電壓:2.3 V ~ 5.5 V 電壓 - 壓降（標(biāo)準(zhǔn)）:0.035V @ 150mA 穩(wěn)壓器數(shù)量:2 電流 - 輸出:150mA 電流 - 限制（最?。?300mA 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:6-UFDFN 裸露焊盤(pán)，6-TMLF? 供應(yīng)商設(shè)備封裝:6-TMLF?（1.6x1.6） 包裝:Digi-Reel® 產(chǎn)品目錄頁(yè)面:1104 (CN2011-ZH PDF) 其它名稱:576-3018-6 |
| LX8117-33CDDT | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:Positive Fixed Voltage Regulator |
| LX8117-33CDT | 功能描述:IC REG LDO 3.3V DPAK RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 系列:- 標(biāo)準(zhǔn)包裝:3,000 系列:- 穩(wěn)壓器拓?fù)浣Y(jié)構(gòu):正，固定式和可調(diào)式 輸出電壓:3.3V，1.25 V ~ 5.7 V 輸入電壓:4.5 V ~ 7 V 電壓 - 壓降（標(biāo)準(zhǔn)）:1.1V @ 1A 穩(wěn)壓器數(shù)量:2 電流 - 輸出:1A 電流 - 限制（最小）:1A 工作溫度:0°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:TO-252-5，DPak（4 引線 + 接片），TO-252AD 供應(yīng)商設(shè)備封裝:PPAK 包裝:管件 其它名稱:497-3576-5 |
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