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參數(shù)資料
| 型號： | LP2957AIS |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 基準電壓源/電流源 |
| 英文描述： | 5V Low-Dropout Regulator for P Applications |
| 中文描述： | 5 V FIXED POSITIVE LDO REGULATOR, 0.8 V DROPOUT, PSSO5 |
| 封裝： | PLASTIC, TO-263, 5 PIN |
| 文件頁數(shù)： | 11/14頁 |
| 文件大小： | 378K |
| 代理商： | LP2957AIS |
Application Hints
(Continued)
Solving for R2:
DESIGN EXAMPLE
#
2:
A 5V regulated output is to be powered from a battery made
up of six NiCad cells. The cell data is:
cell voltage (full charged): 1.4V
cell voltage (90% discharged): 1.0V
The internal impedance of a typical battery is low enough
that source loading during regulator turn-on is not usually a
problem.
In a battery-powered application, the turn-off voltage V
should be selected so that the regulator is shut down when
the batteries are about 90% discharged (over discharge can
damage rechargeable batteries).
In this case, the battery voltage will be
6.0V
at the 90% dis-
charge point (since there are six cells at 1.0V each). That
means for this application, V
OFF
will be set to 6.0V.
Selecting the optimum voltage for V
requires understand-
ing battery behavior. If a Ni-Cad battery is nearly discharged
(cell voltage 1.0V)
and the load is removed
, the cell volt-
age will drift back up. The voltage where the regulator turns
on must be set high enough to keep the regulator from
re-starting during this time, or an on-off pulsing mode can oc-
cur.
If the regulator restarts when the discharged cell voltage
drifts up, the load on the battery will cause the cell voltage to
fall below the turn-off level, which causes the regulator to
shut down. The cell voltage will again float up and the on-off
cycling will continue.
For NiCad batteries, a good cell voltage to use to calculate
V
is about 1.2V per cell. In this application, this will yield a
value for V
ON
of 7.2V.
We can now find R1, R2 and R3 assuming:
V
OFF
= 6.0V
V
ON
= 7.2V
R3 = 49.9k
Solving for R1:
Solving for R2:
www.national.com
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LP2957AIS/NOPB | 功能描述:IC REG LDO 5V .25A TO-263-5 RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 系列:- 標準包裝:1 系列:- 穩(wěn)壓器拓撲結(jié)構(gòu):正，固定式 輸出電壓:4V 輸入電壓:最高 16V 電壓 - 壓降（標準）:0.28V @ 150mA 穩(wěn)壓器數(shù)量:1 電流 - 輸出:150mA 電流 - 限制（最小）:- 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:5-VFBGA 供應(yīng)商設(shè)備封裝:5-uSMD 包裝:Digi-Reel® 其它名稱:LP2985AIBP-4.0DKR |
| LP2957AIS/NOPB | 制造商:Texas Instruments 功能描述:Voltage Regulator IC |
| LP2957AISX | 功能描述:低壓差穩(wěn)壓器 - LDO 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(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 |
| LP2957AISX/NOPB | 功能描述:低壓差穩(wěn)壓器 - LDO 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(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 |
| LP2957AIT | 功能描述:低壓差穩(wěn)壓器 - LDO 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(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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