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參數(shù)資料
| 型號： | LTC1698ES |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Isolated Secondary Synchronous Rectifier Controller |
| 中文描述： | SWITCHING CONTROLLER, PDSO16 |
| 封裝： | 0.150 INCH, PLASTIC, SO-16 |
| 文件頁數(shù)： | 13/24頁 |
| 文件大?。?/td> | 1047K |
| 代理商： | LTC1698ES |
13
LTC1698
1698f
supply must cross the isolation boundary. Coupling this
signal requires an element that will withstand the isolation
potentials and still transfer the loop error signal.
Optocouplers are widely used for this function due to their
ability to couple DC signals. To properly apply them, a
number of factors must be considered. The gain, or
current transfer ratio (CTR) through an optocoupler is
loosely specified and is a strong function of the input
current through the diode. It changes considerably as a
function of time (aging) and temperature. The amount of
aging accelerates with higher operating current. This
variation directly affects the overall loop gain of the sys-
tem. To be an effective optical detector, the output transis-
tor of the optocoupler must have a large base area to
collect the light energy. This gives it a large collector to
base capacitance which can introduce a pole into the
feedback loop. This pole varies considerably with the
current and interacts with the overall loop frequency
compensation network.
The common collector optocoupler configuration removes
the miller effect due to the parasitic capacitance and
increases the frequency response. Figure 7 shows the
optocoupler feedback circuitry using the common collec-
tor approach. Note that the terms R
D
, CTR, C
DE
and r
π
vary
from part to part. They also change with bias current. The
dominant pole of the opto feedback is due to R
F
and C
F
. The
feedforward capacitor C
K
at the optocoupler creates a low
frequency zero. This zero should be chosen to provide a
phase boost at the loop crossover frequency. The parallel
combination of R
K
and R
D
form a high frequency pole with
C
K
. For most optocouplers, R
D
is 50
at a DC bias of 1mA,
and 25
at a DC bias of 2mA. The CTR term is the small
signal AC current transfer ratio. For the QT Optoelectron-
ics MOC207 optocoupler used here, the AC CTR is around
1, even though the DC CTR is much lower when biased at
1mA or 2mA. The first denominator term in the V
C
/V
OUT
equation has been simplified and assumes that C
FB
<<C
C
.
The actual term is:
s R
C
C
s R
C
C
C
C
C
FB
C
C
FB
C
FB
(
)
+
2
1
+
+
APPLICATIOU
W
U
U
V
V
s C
)(
R
s R
C
s R
C
s R
C
s C
R
R
R
R
R
R
CTR
R
+
s r
C
s R
C
C
OUT
C
+
C
C
C
FB
K
K
K
K
D
K
D
F
D
K
DE
F
F
=
+
+
+
+
+
+
π
–
(
)
)
(
)
(
)(
)
1
2
1
5
1
1
1
1
1
1
where
R
CTR
C
r
π
Optocouplerdiode equivalentsmall signalresis
Optocouplercurrent transferratio
Optocouplernonlinearcapacitoracrossbase to emitter
Optocouplersmall signalresis
ce
ce across the base emitter
D
DE
:
tan
tan
=
=
=
=
20k
V
REF
V
COMP
C
C
C
FB
R
C
V
REF
R2
V
OUT
LTC1698
V
FB
1698 F07
100k
OPTODRV
R
K
C
K
MOC207
–
+
–
+
V
REF
LT3781
V
FB
V
CC
C
F
V
C
R
F
R1
R
E
–
+
Figure 7. Error Signal Feedback
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| LTC1698ES#PBF | 功能描述:IC REG CTRLR ISO PWM CM 16-SOIC RoHS:是 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:2,000 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:50% 電源電壓:9 V ~ 10 V 降壓:無 升壓:是 回掃:是 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:8-TSSOP（0.173"，4.40mm 寬） 包裝:帶卷 (TR) |
| LTC1698ES#TR | 功能描述:IC REG CTRLR ISO PWM CM 16-SOIC 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:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 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 ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC1698ES#TRPBF | 功能描述:IC REG CTRLR ISO PWM CM 16-SOIC RoHS:是 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:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 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 ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC1698IGN | 功能描述:IC REG CTRLR ISO PWM CM 16-SSOP 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:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 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 ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC1698IGN#PBF | 功能描述:IC REG CTRLR ISO PWM CM 16-SSOP 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:2,000 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:50% 電源電壓:9 V ~ 10 V 降壓:無 升壓:是 回掃:是 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:8-TSSOP（0.173"，4.40mm 寬） 包裝:帶卷 (TR) |
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