- 您现在的位置：买卖IC网 > PDF目录15304 > LT3837EFE#TRPBF (Linear Technology)IC REG CTRLR FLYBK ISO 16-TSSOP PDF资料下载
参数资料
| 型号： | LT3837EFE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR FLYBK ISO 16-TSSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 250kHz |
| 占空比： | 88% |
| 电源电压： | 4.5 V ~ 20 V |
| 降压： | 无 |
| 升压： | 无 |
| 回扫： | 是 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 是 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 包装： | 带卷 (TR) |
第1页第2页第3页第4页第5页第6页第7页第8页第9页当前第10页第11页第12页第13页第14页第15页第16页第17页第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页
LT3837
OPERATION
V FLBK =
? V FB
The LT3837 is a current mode switcher controller IC
designed specifically for use in an isolated flyback topology
employing synchronous rectification. The LT3837 operation
is similar to traditional current mode switchers. The major
difference is that output voltage feedback is derived via
sensing the output voltage through the transformer. This
precludes the need of an optoisolator in isolated designs
greatly improving dynamic response and reliability. The
LT3837 has a unique feedback amplifier that samples a
transformer winding voltage during the flyback period and
uses that voltage to control output voltage.
The internal blocks are similar to many current mode
controllers. The differences lie in the flyback feedback
amplifier and load compensation circuitry. The logic block
also contains circuitry to control the special dynamic
requirements of flyback control.
amplifier then compares the voltage to the internal bandgap
reference. The feedback amp is actually a transconductance
amplifier whose output is connected to V C only during a
period in the flyback time. An external capacitor on the V C
pin integrates the net feedback amp current to provide the
control voltage to set the current mode trip point.
The regulation voltage at the FB pin is nearly equal to the
bandgap reference V FB because of the high gain in the
overall loop. The relationship between V FLBK and V FB is
expressed as:
R1 + R2
R2
Combining this with the previous V FLBK expression yields
an expression for V OUT in terms of the internal reference,
programming resistors and secondary resistances:
V OUT = ?
(
? V FB ? N SF ? –I SEC ? ESR + R DS(ON)
See Application Note 19 for more information on the
basics of current mode switcher/controllers and isolated
flyback converters.
? R1 + R2
? R2
?
?
)
( )
? V OUT + I SEC ? ESR + R DS(ON)
( N SF ) ( V FB )
?
?
V OUT + I SEC ? ( ESR + R DS(ON) )
V FLBK =
FeedbackAmplifier—PseudoDCTheory
For the following discussion refer to the simplified
Flyback Feedback Amplifier diagram. When the primary side
MOSFET switch MP turns off, its drain voltage rises above
the V IN rail. Flyback occurs when the primary MOSFET is
off and the synchronous secondary MOSFET is on. Dur-
ing flyback the voltage on nondriven transformer pins is
determined by the secondary voltage. The amplitude of this
flyback pulse as seen on the third winding is given as:
N SF
R DS(ON) = on resistance of the synchronous MOSFET M S
I SEC = transformer secondary current
ESR = impedance of secondary circuit capacitor, winding
and traces
N SF = transformer effective secondary-to-feedback winding
turns ratio (i.e., N S /N FLBK )
Rearranging yields the equation for R1.
?
R1 = R2 ? ? – 1 ?
? ?
The effect of nonzero secondary output impedance is dis-
cussed in further detail; see Load Compensation Theory.
The practical aspects of applying this equation for V OUT
are found in the Applications Information section.
Feedback Amplifier Dynamic Theory
So far, this has been a pseudo-DC treatment of flyback
feedback amplifier operation. But the flyback signal is a
pulse, not a DC level. Provision must be made to enable
the flyback amplifier only when the flyback pulse is present.
This is accomplished by the “Enable” line in the diagram.
Timing signals are then required to enable and disable the
flyback amplifier. There are several timing signals which
are required for proper LT3837 operation. Please refer to
the Timing Diagram.
The flyback voltage is then scaled by an external resistive
divider R1/R2 and presented at the FB pin. The feedback
3837fd
10
相关PDF资料 |
PDF描述 |
|---|---|
| GBM43DCBS | CONN EDGECARD 86POS R/A .156 SLD |
| UVY1E102MPD | CAP ALUM 1000UF 25V 20% RADIAL |
| VE-J2X-EY-F1 | CONVERTER MOD DC/DC 5.2V 50W |
| LTC1735CF#TR | IC REG CTRLR BUCK PWM CM 20TSSOP |
| IMC1210EB82NJ | INDUCTOR WW 82NH 5% 1210 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3837IFE#PBF | 功能描述:IC REG CTRLR FLYBK ISO 16-TSSOP 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:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LT3837IFE#TRPBF | 功能描述:IC REG CTRLR FLYBK ISO 16-TSSOP 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:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LT383L313 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Optoelectronic |
| LT3844 | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Voltage, Current Mode Switching Regulator Controller with Programmable Operating Frequency |
| LT3844EFE | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Voltage, Current Mode Switching Regulator Controller with Programmable Operating Frequency |
发布紧急采购，3分钟左右您将得到回复。