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參數(shù)資料
| 型號： | LT1424CN8-5 |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| 中文描述： | 1.9 A SWITCHING REGULATOR, 320 kHz SWITCHING FREQ-MAX, PDIP8 |
| 封裝： | 0.300 INCH, PLASTIC, DIP-8 |
| 文件頁數(shù)： | 8/16頁 |
| 文件大?。?/td> | 141K |
| 代理商： | LT1424CN8-5 |
8
LT1424-5
OPERATIO
The LT1424-5 is a current mode switching regulator IC
that has been designed specifically for the isolated fly-
back topology. The special problem normally encoun-
tered in such circuits is that information relating to the
output voltage on the isolated secondary side of the
transformer must be communicated to the primary side
in order to maintain regulation. Historically, this has been
done with optoisolators or extra transformer windings.
Optoisolator circuits waste output power and the extra
components they require increase the cost and physical
volume of the power supply. Optoisolators can also
exhibit trouble due to limited dynamic response (tempo-
ral), nonlinearity, unit-to-unit variation and aging over
life. Circuits employing extra transformer windings also
exhibit deficiencies. The extra winding adds to the
transformer’s physical size and cost. Dynamic response
is often mediocre. There is usually no method for main-
taining load regulation versus load.
The LT1424-5 derives its information about the isolated
output voltage by examining the primary side flyback
pulse waveform. In this manner no optoisolator nor extra
transformer winding is required. This IC is a quantum
improvement over previous approaches because: target
output voltage is programmed by resistor ratio, regula-
tion is maintained well into discontinuous mode and
optional load compensation is available.
The Block Diagram shows an overall view of the system.
Many of the blocks are similar to those found in tradi-
tional designs including: internal bias regulator, oscilla-
tor, logic, current amplifier and comparator, driver and
output switch. The novel sections include a special
flyback error amplifier and a load compensation mecha-
nism. Also, due to the special dynamic requirements of
flyback control, the logic system contains additional
functionality not found in conventional designs.
The R
REF
, R
FB
and R
OCOMP
resistors in the Block Diagram
are application-specific thin-film resistors internal to the
LT1424-5. The capacitor connected to the R
CCOMP
pin is
external.
The LT1424-5 operates much the same as traditional
current mode switchers, the major difference being a
different type of error amplifier which derives its feedback
U
information from the flyback pulse. Due to space con-
straints, this discussion will not reiterate the basics of
current mode switcher/controllers and isolated flyback
converters. A good source of information on these topics
is LTC’s Application Note 19.
ERROR AMPLIFIER—PSEUDO DC THEORY
Please refer to the simplified diagram of the Flyback Error
Amplifier. Operation is as follows: when output switch Q4
turns off, its collector voltage rises above the V
IN
rail. The
amplitude of this flyback pulse, i.e., the difference between
it and V
IN
, is given as:
V
FLBK
=
V
F
= D1 forward voltage
I
SEC
= Transformer secondary current
ESR = Total impedance of secondary circuit
N
SP
= Transformer effective secondary-to-primary
turns ratio
V
OUT
+ V
F
+ (I
SEC
)(ESR)
N
SP
The flyback voltage is then converted to a current by the
action of R
FB
and Q1. Nearly all of this current flows
through resistor R
REF
to form a ground-referred voltage.
This is then compared to the internal bandgap reference by
the differential transistor pair Q2/Q3. The collector current
from Q2 is mirrored around and subtracted from fixed
current source I
FXD
at the V
C
pin. An external capacitor
integrates this net current to provide the control voltage to
set the current mode trip point.
The relatively high gain in the overall loop will then cause
the voltage at the R
REF
resistor to be nearly equal to the
bandgap reference V
BG
. The relationship between V
FLBK
and V
BG
may then be expressed as:
V
FLBK
R
FB
V
FLBK
= V
BG
α
= Ratio of Q1 I
C
to I
E
V
BG
= Internal bandgap reference
α
=
or,
R
FB
R
REF
V
BG
R
REF
)
)
1
α
)
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相關代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LT1424CN8-5#PBF | 功能描述:IC REG FLYBACK ISOLATED 5V 8DIP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關穩(wěn)壓器 系列:- 標準包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關:- 電流 - 輸出:50mA 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:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應商設備封裝:10-MSOP 裸露焊盤 |
| LT1424CN8-9 | 功能描述:IC REG FLYBACK ISOLATED 9V 8DIP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關穩(wěn)壓器 系列:- 標準包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關:- 電流 - 輸出:50mA 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:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應商設備封裝:10-MSOP 裸露焊盤 |
| LT1424CN8-9#PBF | 功能描述:IC REG FLYBACK ISOLATED 9V 8DIP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關穩(wěn)壓器 系列:- 標準包裝:20 系列:SIMPLE SWITCHER® 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:12V 輸入電壓:4 V ~ 60 V PWM 型:電壓模式 頻率 - 開關:52kHz 電流 - 輸出:1A 同步整流器:無 工作溫度:-40°C ~ 125°C 安裝類型:通孔 封裝/外殼:16-DIP（0.300"，7.62mm） 包裝:管件 供應商設備封裝:16-DIP 其它名稱:*LM2575HVN-12LM2575HVN-12 |
| LT1424CS8 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Current-Mode SMPS Controller |
| LT1424CS8-5 | 功能描述:IC REG FLYBACK ISOLATED 5V 8SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關穩(wěn)壓器 系列:- 標準包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關:- 電流 - 輸出:50mA 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:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應商設備封裝:10-MSOP 裸露焊盤 |
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