- 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： | 15/28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页第10页第11页第12页第13页第14页当前第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
APPLICATIONS INFORMATION
tight coupling usually increases primary-to-secondary
capacitance and limits the primary-to-secondary break-
down voltage, so it isn’t always practical.
Primary Inductance
The transformer primary inductance, L P , is selected based
on the peak-to-peak ripple current ratio (X) in the trans-
former relative to its maximum value. As a general rule,
keep X in the range of 50% to 70% ripple current (i.e., X =
0.5 to 0.7). Higher values of ripple will increase conduction
losses, while lower values will require larger cores.
Ripple current and percentage ripple is largest at minimum
duty cycle; in other words, at the highest input voltage.
L P is calculated from:
L P = ( V IN(MAX) ? DC MIN ) 2 = ( V IN(MAX) ? DC MIN ) 2 ? Eff
f OSC ? X MAX ? P IN f OSC ? X MAX ? P OUT
Transformer Core Selection
Once L P is known, the type of transformer is selected.
High efficiency converters use ferrite cores to minimize
core loss. Actual core loss is independent of core size for
a fixed inductance, but decreases as inductance increases.
Since increased inductance is accomplished through
more turns of wire, copper losses increase. Thus trans-
former design balances core and copper losses. Remem-
ber that increased winding resistance will degrade cross
regulation and increase the amount of load compensa-
tion required.
The main design goals for core selection are reducing
copper losses and preventing saturation. Ferrite core mate-
rial saturates hard, rapidly reducing inductance when the
peak design current is exceeded. This results in an abrupt
increase in inductor ripple current and, consequently, out-
put voltage ripple. Do not allow the core to saturate! The
maximum peak primary current occurs at minimum V IN :
? ? 1 + MIN ?
where:
f OSC is the OSC frequency
I PK =
P IN ? X ?
V IN(MIN) ? DC MAX ? 2 ?
P IN =
= 37.5W
DC MIN =
=
= 35.5%
N ? V IN(MAX) 1 18
1 + 1 + ?
V OUT
( 18V ? 0.355 ) 2
L P = = 7.8 μ H
DC MAX =
=
= 52.4%
N ? V IN(MIN) 1 9
1 + 1 + ?
V OUT
X MIN = ( V IN(MIN) ? DC MAX ) 2 = ( 9 ? 0.52 ) 2
I PK =
? ? 1 +
? = 9.47A
DC MIN istheDCatmaximuminputvoltage
X MAX is ripple current ratio at maximum input voltage
Continuing with the 9V to 3.3V example, let us assume a
10A output, 9V to 18V input power with 88% efficiency.
Using X = 0.7, and f OSC = 200kHz:
3.3 ? 10A
88%
1 1
3 3.3
200kHz ? 0.7 ? 37.5W
Optimization might show that a more efficient solution
is obtained at higher peak current but lower inductance
and the associated winding series resistance. A simple
spreadsheet program is useful for looking at tradeoffs.
now :
1 1
3 3.3
f OSC ? L P ? P IN 200kHz ? 7.8 μ H ? 37.5W
= 0.380
Using the example numbers leads to:
37.5W ? 0.380 ?
9V ? 0.524 ? 2 ?
Multiple Outputs
One advantage that the flyback topology offers is that ad-
ditional output voltages can be obtained simply by adding
windings. Designing a transformer for such a situation is
beyond the scope of this document. For multiple windings,
realize that the flyback winding signal is a combination of
activity on all the secondary windings. Thus load regulation
is affected by each windings load. Take care to minimize
cross regulation effects.
3837fd
15
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。