- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄377702 > LT1432CN8 (LINEAR TECHNOLOGY CORP) 5V High Efficiency Step-Down Switching Regulator Controller PDF資料下載
參數(shù)資料
| 型號： | LT1432CN8 |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 5V High Efficiency Step-Down Switching Regulator Controller |
| 中文描述： | SWITCHING CONTROLLER, PDIP8 |
| 封裝： | PLASTIC, DIP-8 |
| 文件頁數(shù)： | 19/28頁 |
| 文件大?。?/td> | 611K |
| 代理商： | LT1432CN8 |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁第10頁第11頁第12頁第13頁第14頁第15頁第16頁第17頁第18頁當前第19頁第20頁第21頁第22頁第23頁第24頁第25頁第26頁第27頁第28頁
19
LT1432
U
S
A
O
PPLICATI
U
U
average, so a ten year life is only 15,000 hours. The
manufacturer should be consulted for a final blessing. See
Application Note 46 for specific formulas for calculating
the life time or allowed ripple current in capacitors.
The reason for all this attention to ripple rating is that
everyone is in a size squeeze, and the temptation is to use
the smallest possible components. Do not cheat here
folks, or you may be faced with costly field failures.
ESR on the output capacitor determines output voltage
ripple, so this is also of much concern. Mother Nature has
decreed that for a given capacitor technology, ESR is a
direct function of the volumeof the capacitor. In other
words, if you want low ESR you must consume space This
is quickly confirmed by scanning the ESR numbers for a
wide range of capacitor values and voltage ratings within
a given family of capacitors. It is immediately obvious that
can size determines ESR, not capacitance, or voltage
rating. The only way to cheat on this limitation is to find the
best family of capacitors. Manufacturers such as Nichicon,
Chemicon, and Sprague should be checked. Sanyo makes
a very low ESR capacitor type know as OSCON, utilizing a
semiconductor dielectric. Its major disadvantage is some-
what higher price, and a tendency to make regulator
feedback loops unstable because of its extremely low ESR.
Most switching regulator loops depend to some extent on
the output capacitor ESR for a phase lead!
Output Filters
Output ripple voltage at the switching frequency is a fact of
life with switching regulators. Everyone knows that this
ripple must be held below some level to guarantee that it
does not affect system performance. The question is, what
is that level For sensitive analog systems with wide
bandwidths, supply ripple may have to be a 1mV or less.
Digital systems can often tolerate 400mV
p-p
ripple with no
effect on performance. In most of these digital applica-
tions of the LT1432 as a buck converter, an output filter is
not needed because output ripple is normally in the 25mV
to 100mV
p-p
range without a filter. Note that burst mode
ripple is at low frequencies where small output filters are
not effective. The decision to add an output filter does
allow the main filter capacitor to get smaller, so the overall
board space may not increase prohibitively. See the dis-
cussion of waveforms for load transient response implica-
tions when adding a filter.
If modest reductions in output ripple are required, one can
increase the size of the main inductor and/or the output
capacitor. Buck converters are easier than other types
because the main inductor acts as a filter element. The
square wave voltage is converted to a triangular current
before being fed to the output capacitor. Actually, at
switching frequencies, the output capacitor is resistive
and output ripple voltage is determined not by the capaci-
tor value in
μ
F, but rather by the capacitor effective series
resistance (ESR). This parameter is determined by capaci-
tor volume within any given family, so to get ESR down,
one must still use a “bigger” capacitor. The problem is that
often the main inductor/capacitor becomes physically too
large if low output ripple is needed. Inverters, such as the
positive to negative converter, tend to have much higher
output ripple voltage because the main inductor is not a
filter element – it simply acts as an energy storage device
for shuttling essentially square wave currents from input
to output. Unlike the buck converter, these currents can be
much higher in amplitude than the output current.
An output filter of very modest size can reduce normal
mode output ripple voltage by a factor of ten or more. The
formula for filter attenuation in buck converters and invert-
ers is shown below.
Attenuation
ESR
8 L f
ESR
4 L f
=
(BUCK CONVERTER)
(INVERTER)
(The factor “4” is an
approximation
assuming worst case
duty cycle of 50%)
A 10
μ
H, 100
μ
F (ESR = 0.4
) filter on a buck converter
using a 60kHz LT1271 will give an attenuation of:
Attenuation
=
(
)
0.4
–6
8 10E
60E
0.083
3
=
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LT1432CN8-3.3 | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| LT1432CS8 | 5V High Efficiency Step-Down Switching Regulator Controller |
| LT1432CS8-3.3 | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| LT1457ACN8 | Dual, Precision JFET Input Op Amp |
| LT1457CN8 | Dual, Precision JFET Input Op Amp |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LT1432CN8-3.3 | 功能描述:IC REG CTRLR BUCK PWM 8-DIP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| LT1432CS8 | 制造商:Linear Technology 功能描述: |
| LT1432CS8-3.3 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:3.3V High Efficiency Step-Down Switching Regulator Controller |
| LT1435 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:4.5A, 500kHz Step-Down Switching Regulator |
| LT1436 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:4.5A, 500kHz Step-Down Switching Regulator |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。