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參數(shù)資料
| 型號： | MIC29311-5.1BU |
| 廠商： | MICREL INC |
| 元件分類： | 基準電壓源/電流源 |
| 英文描述： | 3A Fast-Response LDO Regulator for USB Preliminary Information |
| 中文描述： | 5.1 V FIXED POSITIVE LDO REGULATOR, 1 V DROPOUT, PSSO5 |
| 封裝： | TO-263, 5 PIN |
| 文件頁數(shù)： | 8/12頁 |
| 文件大小： | 135K |
| 代理商： | MIC29311-5.1BU |
MIC29311
Applications Information
The MIC29311 is a high-performance low-dropout voltage
regulator suitable for all moderate to high-current voltage
regulator applications. The 600mV dropout voltage at full
load makes it especially valuable in battery-powered systems
and as high-efficiency noise filters in “post-regulator” applica-
tions. Its unique output voltage makes the MIC39311 ideal for
Universal Serical Bus (USB) power switching applications.
Unlike older NPN-pass transistor designs, where the mini-
mum dropout voltage is limited by the base-emitter voltage
drop and collector-emitter saturation voltage, dropout perfor-
mance of the PNP output of these devices is limited merely
by the low V
CE
saturation voltage.
A trade-off for the low dropout voltage is a varying base drive
requirement. But Micrel’s Super
β
eta PNP process re-
duces this drive requirement to merely 1% to 5% of the load
current.
The MIC29311 regulator is fully protected from damage due
to fault conditions. Current limiting is provided. This limiting is
linear; output current under overload conditions is constant.
Thermal shutdown disables the device when the die tem-
perature exceeds the maximum safe operating temperature.
Transient protection allows device (and load) survival even
when the input voltage spikes above and below nominal. The
output structure of these regulators allows voltages in excess
of the desired output voltage to be applied without reverse
current flow. The MIC29311 version offers a logic level on-off
control: when disabled, the device draws nearly zero current.
Micrel
MIC29311
8
December 1998
MIC29311-5.1
IN
EN
OUT
FLG
GND
V
IN
V
OUT
Flag
Enable
Shutdown
Figure 1. Input and Output Capacitors
Thermal Design
Linear regulators are simple to use. The most complicated
design parameters to consider are thermal characteristics.
Thermal design requires the following application-specific
parameters:
Maximum ambient temperature, T
A
Output Current, I
OUT
Output Voltage, V
OUT
Input Voltage, V
IN
First, calculate the power dissipation of the regulator from
these numbers and the device parameters from this datasheet.
(
Where the ground current is approximated by 2% of I
OUT
.
Then the heat sink thermal resistance is determined by:
P
I
1.02V
V
D
OUT
IN
OUT
=
)
θ
θ
θ
SA
J(max)
T
A
D
JC
CS
T
P
=
+
Where T
J (max)
≤
125
°
C and
θ
CS
is between 0 and 2
°
C/W.
The heat sink may be significantly reduced in applications
where the minimum input voltage is known and is large
compared with the dropout voltage. Use a series input
resistor to drop excessive voltage and distribute the heat
between this resistor and the regulator. The low dropout
properties of Micrel Super eta PNP regulators allow very
significant reductions in regulator power dissipation and the
associated heat sink without compromising performance.
When this technique is employed, a capacitor of at least 1
μ
F
is needed directly between the input and regulator ground.
Please refer to Application Note 9 for further details and
examples on thermal design and heat sink specification.
Capacitor Requirements
For stability and minimum output noise, a capacitor on the
regulator output is necessary. The value of this capacitor is
dependent upon the output current; lower currents allow
smaller capacitors. The MIC29311 regulator is stable with a
minimum capacitor value of 10
μ
F at full load.
This capacitor need not be an expensive low ESR type:
aluminum electrolytics are adequate. In fact, extremely low
ESR capacitors may contribute to instability. Tantalum ca-
pacitors are recommended for systems where fast load
transient response is important.
Where the regulator is powered from a source with a high AC
impedance, a 0.1
μ
F capacitor connected between Input and
GND is recommended. This capacitor should have good
characteristics to above 250kHz. When the regulator is
located more than 3 inches from the ac bulk supply capaci-
tors, a 1
μ
F or greater input capacitor is recommended.
Minimum Load Current
The MIC29311 regulator is specified between finite loads. If
the output current is too small, leakage currents dominate
and the output voltage rises. A 10mA minimum load current
is necessary for proper regulation.
Enable Input
The MIC29311 version features an enable (EN) input that
allows on-off control of the device. Special design allows
“zero” current drain when the device is disabled—only micro-
amperes of leakage current flows. The EN input has TTL/
CMOS compatible thresholds for simple interfacing with
logic, or may be directly tied to V
IN
. Enabling the regulator
requires approximately 20
μ
A of current into the EN pin.
Error Flag
The MIC29311 features an error flag which looks at the output
voltage and signals an error condition when this voltage
drops 5% below its expected value. The error flag is an open-
collector output that pulls low under fault conditions. It may
sink 10mA. Low output voltage signifies a number of possible
problems, including an overcurrent fault (the device is in
current limit) and low input voltage. The flag output is inopera-
tive during overtemperature shutdown conditions.
USB Applications
The main application of the MIC29311 is to control power
distribution in a self-powered Universal Serial Bus hub. For
self-powered hubs, the MIC29311 provides 5.1V
±
3% to
downstream ports from an unregulated supply voltage (see
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MIC29312BT | 功能描述:IC REG LDO ADJ 3A TO-220-5 RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 系列:- 標準包裝:3,000 系列:- 穩(wěn)壓器拓撲結(jié)構(gòu):正，固定式 輸出電壓:3.8V 輸入電壓:最高 16V 電壓 - 壓降（標準）:0.3V @ 80mA 穩(wěn)壓器數(shù)量:1 電流 - 輸出:80mA 電流 - 限制（最?。?- 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:SC-74A，SOT-753 供應(yīng)商設(shè)備封裝:SOT-23-5 包裝:帶卷 (TR) 其它名稱:MIC5203-3.8BM5TRMIC5203-3.8BM5TR-ND |
| MIC29312BTL3 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| MIC29312BU | 功能描述:IC REG LDO ADJ 3A TO-263-5 RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 系列:- 標準包裝:3,000 系列:- 穩(wěn)壓器拓撲結(jié)構(gòu):正，固定式 輸出電壓:3.8V 輸入電壓:最高 16V 電壓 - 壓降（標準）:0.3V @ 80mA 穩(wěn)壓器數(shù)量:1 電流 - 輸出:80mA 電流 - 限制（最?。?- 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:SC-74A，SOT-753 供應(yīng)商設(shè)備封裝:SOT-23-5 包裝:帶卷 (TR) 其它名稱:MIC5203-3.8BM5TRMIC5203-3.8BM5TR-ND |
| MIC29312BU TR | 功能描述:IC REG LDO ADJ 3A TO-263-5 RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 系列:- 標準包裝:3,000 系列:- 穩(wěn)壓器拓撲結(jié)構(gòu):正，固定式 輸出電壓:3.8V 輸入電壓:最高 16V 電壓 - 壓降（標準）:0.3V @ 80mA 穩(wěn)壓器數(shù)量:1 電流 - 輸出:80mA 電流 - 限制（最?。?- 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:SC-74A，SOT-753 供應(yīng)商設(shè)備封裝:SOT-23-5 包裝:帶卷 (TR) 其它名稱:MIC5203-3.8BM5TRMIC5203-3.8BM5TR-ND |
| MIC29312WT | 功能描述:低壓差穩(wěn)壓器 - LDO 3.0A LDO Adj. + Shutdown (ROHS Compliant) 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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