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參數(shù)資料
| 型號(hào)： | LMS5258 |
| 廠商： | National Semiconductor Corporation |
| 元件分類： | 基準(zhǔn)電壓源/電流源 |
| 英文描述： | 150mA, Cap, Low Dropout Voltage Regulator with Power Good |
| 中文描述： | 150毫安，帽，低壓差線性穩(wěn)壓器的電源良好 |
| 文件頁(yè)數(shù)： | 8/9頁(yè) |
| 文件大?。?/td> | 515K |
| 代理商： | LMS5258 |
Application Notes
LMS5258 is a linear regulator designed to be used with a low
ESR, low cost ceramic capacitors.
EXTERNAL CAPACITORS
The LMS5258 regulator requires an output capacitor to
maintain stability. The capacitor must be at least 1μF or
greater. The capacitor can be low-ESR ceramic chip capaci-
tor, however for improved capacitance over temperature,
tantalum capacitors can be used.
A 1μF input capacitor is recommended when the supply
capacitance is more than 10 inches away from the device, or
when the supply is a battery.
X7R dielectric ceramic capacitors are recommended be-
cause of their temperature performance. X7R-type capaci-
tors change capacitance by 15% over their operating tem-
perature range and are the most stable type of ceramic
capacitors. Z5U and Y5V dielectric capacitors change value
by as much 50% and 60% respectively over their operating
temperature range. To use a ceramic chip capacitor with Y5V
dielectric, the value must be much higher than an X7R
ceramic or a tantalum capacitor to ensure the same mini-
mum capacitance value over the operating temperature
range. Tantalum capacitors have a very stable dielectric
(10% over their operating temperature range) and can also
be used with this device.
ENABLE/SHUTDOWN
The LMS5258 has an active high enable pin that allows the
regulator to be disabled. Applying a Logic Level low (
<
0.4 V)
to the Shutdown pin will cause the output to turn off, in this
state current consumed by the regulator goes nearly to zero.
Applying a logic level high (
>
2.0) enables the output voltage.
The enable/shutdown pin can’t be left floating; a floating
enable pin may cause an indeterminate state on the output.
ACTIVE SHUTDOWN
The LMS5258 designed with a N-channel MOSFET that acts
as a shutdown clamp. The N-channel turns on when the
device is disabled to allow the output capacitor and load to
discharge.
POWER GOOD
The power good output is an open-drain output. It is de-
signed essentially to work as a power-on reset generator
once the regulated voltage was up and/ or a fault condition.
When a fault condition and an undervoltage detection occur,
the output of the power good pin goes low. The power good
output comes back up once the output has reached 97% of
its nominal value and 1ms to 5ms delay has passed , see
timing diagram.
The LMS5258 internal circuit monitors overcurrent, tempera-
ture and falling output voltage. If one of these conditions is
flaged that indicates a fault condition.
The flaged condition output is fed into an onchip delay circuit
that drives the open drain output transistor.
TRANSIENT RESPONSE
The LMS5258 implements a unique output stage to dramati-
cally improve transient response recovery time. The output is
a totem-pole configuration with a P-channel MOSFET pass
device and a N-channel MOSFET clamp. The N-channel
clamp is a significantly smaller device that prevents the
output voltage from overshooting when a heavy load is
removed. This feature helps to speed up the transient re-
sponse by significantly decreasing transient response recov-
ery time during the transition from heavy load to light load.
THERMAL BEHAVIOR
The LMS5258 regulator has internal thermal shutdown to
protect the device from over heating. Under all operating
conditions, the maximum junction temperature of the
LMS5258 must be below 125C. Maximum power dissipation
can be calculated based on the output current and the
voltage drop across the part. The maximum power dissipa-
tion is
P
D(MAX)
= (T
J(MAX)
–T
A
)/
θ
JA
θ
JA
is the junction-to-ambient thermal resistance, 235C/W
for the LMS5258 in the SOT23-5 package. T
A
is the maxi-
mum ambient temperature T
J(MAX)
is the maximum junction
temperature of the die, 125C.
When operating the LMS5258 at room temperature, the
maximum power dissipation is 425mW.
The actual power dissipated by the regulator is
P
D
= (V
IN
– V
OUT
) I
L
+ V
IN
I
GND
Substituting P
, determined above, for P
and solving
for the operating condition that are critical to the application
will give the maximum operating conditions for the regulator
circuit. To prevent the device from entering thermal shut-
down, maximum power dissipation cannot be exceeded.
L
www.national.com
8
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LMS5258A-1.2 E WAF | 制造商:Texas Instruments 功能描述: |
| LMS5258MF-1 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:150mA, Cap, Low Dropout Voltage Regulator with Power Good |
| LMS5258MF-1.2 | 制造商:Texas Instruments 功能描述: 制造商:Texas Instruments 功能描述:IC V REG LDO 0.15A 1.2V SMD 5258 |
| LMS5258MF-1.2 | 制造商:Texas Instruments 功能描述:IC V REG LDO 0.15A 1.2V SMD 5258 |
| LMS5258MF-1.2/NOPB | 功能描述:IC REG LDO 1.2V .15A SOT23-5 RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:2,500 系列:- 穩(wěn)壓器拓?fù)浣Y(jié)構(gòu):正，固定式 輸出電壓:3.1V 輸入電壓:最高 5.5V 電壓 - 壓降（標(biāo)準(zhǔn)）:- 穩(wěn)壓器數(shù)量:1 電流 - 輸出:300mA 電流 - 限制（最?。?420mA 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細(xì)型，TSOT-23-5 供應(yīng)商設(shè)備封裝:TSOT-23-5 包裝:帶卷 (TR) |
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