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參數(shù)資料
| 型號： | LT1941EFE |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Triple Monolithic Switching Regulator |
| 中文描述： | 6 A SWITCHING REGULATOR, 1350 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封裝： | 4.40 MM, PLASTIC, TSSOP-28 |
| 文件頁數(shù)： | 16/24頁 |
| 文件大?。?/td> | 336K |
| 代理商： | LT1941EFE |
16
LT1941
1941f
APPLICATIOU
and is largest when V
IN
= 2 V
OUT
(50% duty cycle). As the
second, lower power channel draws input current, the
input capacitor’s RMS current actually decreases as the
out-of-phase current cancels the current drawn by the
higher power channel. The ripple current contribution
from the third channel will be minimal. Considering that
the maximum load current from a single channel is ~2.8A,
RMS ripple current will always be less than 1.4A.
The high frequency of the LT1941 reduces the energy
storage requirements of the input capacitor, so that the
capacitance required is often less than 10
μ
F. The combi-
nation of small size and low impedance (low equivalent
series resistance or ESR) of ceramic capacitors makes
them the preferred choice. The low ESR results in very low
voltage ripple. Ceramic capacitors can handle larger mag-
nitudes of ripple current than other capacitor types of the
same value. Use X5R and X7R types.
An alternative to a high value ceramic capacitor is a lower
value along with a larger electrolytic capacitor, for ex-
ample a 1
μ
F ceramic capacitor in parallel with a low ESR
tantalum capacitor. For the electrolytic capacitor, a value
larger than 10
μ
F will be required to meet the ESR and
ripple current requirements. Because the input capacitor
is likely to see high surge currents when the input source
is applied, tantalum capacitors should be surge rated. The
manufacturer may also recommend operation below the
rated voltage of the capacitor. Be sure to place the 1
μ
F
ceramic as close as possible to the V
IN
and GND pins on
the IC for optimal noise immunity.
A final caution is in order regarding the use of ceramic
capacitors at the input. A ceramic input capacitor can
combine with stray inductance to form a resonant tank
circuit. If power is applied quickly (for example by plug-
ging the circuit into a live power source), this tank can ring,
doubling the input voltage and damaging the LT1941. The
solution is to either clamp the input voltage or dampen the
tank circuit by adding a lossy capacitor in parallel with the
ceramic capacitor. For details, see Application Note 88.
W
U
U
Frequency Compensation
The LT1941 uses current mode control to regulate the
output. This simplifies loop compensation. In particular, the
LT1941 does not depend on the ESR of the output capaci-
tor for stability so you are free to use ceramic capacitors
to achieve low output ripple and small circuit size.
The components tied to the V
C
pin provide frequency
compensation. Generally, a capacitor and a resistor in
series to ground determine loop gain. In addition, there is
a lower value capacitor in parallel. This capacitor filters
noise at the switching frequency and is not part of the loop
compensation.
Loop compensation determines the stability and transient
performance. Designing the compensation network is a
bit complicated and the best values depend on the appli-
cation and the type of output capacitor. A practical approach
is to start with one of the circuits in this data sheet that is
similar to your application and tune the compensation
network to optimize the performance. Check stability across
all operating conditions, including load current, input volt-
age and temperature. The LT1375 data sheet contains a
more thorough discussion of loop compensation and de-
scribes how to test the stability using a transient load.
Application Note 76 is an excellent source as well.
Figure 5 shows an equivalent circuit for the LT1941
control loop. The error amp is a transconductance ampli-
fier with finite output impedance. The power section,
consisting of the modulator, power switch and inductor is
modeled as a transconductance amplifier generating an
output current proportional to the voltage at the V
C
pin.
Note that the output capacitor integrates this current and
that the capacitor on the V
C
pin (C
C
) integrates the error
amplifier output current, resulting in two poles in the loop.
In most cases, a zero is required and comes either from the
output capacitor ESR or from a resistor in series with C
C
.
This model works well as long as the inductor current
ripple is not too low (
I
RIPPLE
> 5% I
OUT
) and the loop
crossover frequency is less than
SW
/5. A phase lead
capacitor (C
PL
) across the feedback divider may improve
the transient response.
The equivalent circuit for the LT1941 inverter control loop
is slightly different than is shown in Figure 5. The feedback
resistors are connected as shown for negative outputs in
Figure 2. The operational amplifier is fast enough to have
minimal effect on the loop dynamics.
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| LT1941EFE#PBF | 功能描述:IC REG MULTI CONFIG TRPL 28TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 產(chǎn)品培訓模塊:MIC23xxx HyperLight Load™ Regulators 標準包裝:5,000 系列:HyperLight Load® 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.8V 輸入電壓:2.7 V ~ 5.5 V PWM 型:混合物 頻率 - 開關(guān):4MHz 電流 - 輸出:2A 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:8-VFDFN 裸露焊盤，8-MLF? 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-MLF?（2x2） 產(chǎn)品目錄頁面:1094 (CN2011-ZH PDF) 其它名稱:576-3303-2 |
| LT1941EFE#TR | 功能描述:IC REG MULTI CONFIG TRPL 28TSSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 設(shè)計資源:Design Support Tool 標準包裝:1 系列:- 類型:升壓（升壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3V 輸入電壓:0.75 V ~ 2 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:100mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細型，TSOT-23-5 包裝:剪切帶 (CT) 供應(yīng)商設(shè)備封裝:TSOT-23-5 其它名稱:AS1323-BTTT-30CT |
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