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| 型号： | LTC1698ES |
| 厂商： | Linear Technology |
| 文件页数： | 13/24页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR ISO PWM CM 16-SOIC |
| 标准包装： | 50 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 400kHz |
| 电源电压： | 6 V ~ 12.6 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 是 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 16-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1333 (CN2011-ZH PDF) |
LTC1698
APPLICATIO S I FOR ATIO
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
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 2 ? ( C C FB ) ? ? 1 + s ? R C ?
C C + C FB ?
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
+ C
?
?
C C ? C FB ?
?
?
? ? F
? ?
R ? R ? ? R D K ? ( 1 + s ? r π ? C DE F F )
1 + s ? C K ? K D ?
V C
V OUT
= –
( 1 + s ? C C ? R C )
( s ? R 2 ? C C ) ? ( 1 + s ? R C ? C FB )
? 5 ?
?
?
R K + R D ?
( 1 + s ? R K ? C K ) ? R ? CTR ? 1 1
+ R ) ( 1 + s ? R ? C
?
where :
R D = Optocoupler diode equivalent small ? signal resis tan ce
CTR = Optocoupler current transfer ratio
C DE = Optocoupler nonlinear capacitor across base to emitter
r π = Optocoupler small ? signal resis tan ce across the base emitter
LTC1698
LT3781
+
V REF
V CC
R K
C K
OPTODRV
100k
+
–
V REF
20k
+
–
V REF
V FB
V OUT
R2
V C
–
V FB
R E
MOC207
V COMP
C C
R C
R1
C F
R F
Figure 7. Error Signal Feedback
C FB
1698 F07
1698f
13
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1698ES#PBF | 功能描述:IC REG CTRLR ISO PWM CM 16-SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,000 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:1MHz 占空比:50% 电源电压:9 V ~ 10 V 降压:无 升压:是 回扫:是 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 85°C 封装/外壳:8-TSSOP（0.173"，4.40mm 宽） 包装:带卷 (TR) |
| LTC1698ES#TR | 功能描述:IC REG CTRLR ISO PWM CM 16-SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC1698ES#TRPBF | 功能描述:IC REG CTRLR ISO PWM CM 16-SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC1698IGN | 功能描述:IC REG CTRLR ISO PWM CM 16-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC1698IGN#PBF | 功能描述:IC REG CTRLR ISO PWM CM 16-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,000 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:1MHz 占空比:50% 电源电压:9 V ~ 10 V 降压:无 升压:是 回扫:是 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 85°C 封装/外壳:8-TSSOP（0.173"，4.40mm 宽） 包装:带卷 (TR) |
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