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参数资料
| 型号： | DC1561A |
| 厂商： | Linear Technology |
| 文件页数： | 21/42页 |
| 文件大小： | 0K |
| 描述： | EVAL BOARD FOR LTC4278 |
| 设计资源： | DC1561A Design Files |
| 标准包装： | 1 |
| 主要目的： | 电源管理，以太网供电（POE） |
| 嵌入式： | 否 |
| 已用 IC / 零件： | LTC4278 |
| 已供物品： | 板 |
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LTC4278
28
4278fc
APPLICATIONS INFORMATION
when the peak design current is exceeded. This results
in an abrupt increase in inductor ripple current and,
consequently, output voltage ripple. Do not allow the core
to saturate! The maximum peak primary current occurs
at minimum VIN:
IPK =
PIN
VIN(MIN) DCMAX
1+ XMIN
2
now :
DCMAX =
1
1+
N VIN MIN
(
)
VOUT
=
1
1+ 1
8
41
5
=
49.4%
XMIN =
VIN(MIN) DCMAX
(
)
2
fOSC LP PIN
=
41 49.4%
(
)
2
200kHz 260H 29.5W
=
0.267
Using the example numbers leads to:
IPK =
29.5W
41 0.494
1+ 0.267
2
=1.65A
Multiple Outputs
One advantage that the flyback topology offers is that
additionaloutputvoltagescanbeobtainedsimplybyadding
windings. Designing a transformer for such a situation is
beyondthescopeofthisdocument.Formultiplewindings,
realize that the flyback winding signal is a combination of
activityonallthesecondarywindings.Thusloadregulation
is affected by each winding’s load. Take care to minimize
cross regulation effects.
Setting Feedback Resistive Divider
TheexpressionforVOUTdevelopedintheOperationsection
is rearranged to yield the following expression for the
feedback resistors:
R1=R2
VOUT +ISEC ESR+RDS(ON)
(
)
VFB NSF
1
Continuing the example, if ESR + RDS(ON) = 8mW, R2 =
3.32k, then:
R1=3.32k 5
+
5.3 0.008
1.237 1/ 3
1
= 37.28k
choose 37.4k.
It is recommended that the Thevenin impedance of the
resistive divider (R1||R2) is roughly 3k for bias current
cancellation and other reasons.
Current Sense Resistor Considerations
The external current sense resistor is used to control peak
primary switch current, which controls a number of key
converter characteristics including maximum power and
external component ratings. Use a noninductive current
sense resistor (no wire-wound resistors). Mounting the
resistordirectlyaboveanunbrokengroundplaneconnected
with wide and short traces keeps stray resistance and
inductance low.
ThedualsensepinsallowforafullKelvinconnection.Make
sure that SENSE+ and SENSE– are isolated and connect
close to the sense resistor.
Peak current occurs at 100mV of sense voltage VSENSE.So
the nominal sense resistor is VSENSE/IPK. For example, a
peakswitchcurrentof10Arequiresanominalsenseresistor
of 0.010
W Note that the instantaneous peak power in the
sense resistor is 1W, and that it is rated accordingly. The
use of parallel resistors can help achieve low resistance,
low parasitic inductance and increased power capability.
Size RSENSE using worst-case conditions, minimum LP,
VSENSE and maximum VIN. Continuing the example, let us
assume that our worst-case conditions yield an IPKof40%
above nominal, so IPK = 2.3A. If there is a 10% tolerance
on RSENSE and minimum VSENSE = 88mV, then RSENSE
110% = 88mV/2.3A and nominal RSENSE = 35mW. Round
to the nearest available lower value, 33m
W.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| DC1561B | 功能描述:EVAL BOARD FOR LTC4278 RoHS:是 类别:编程器，开发系统 >> 评估演示板和套件 系列:- 标准包装:1 系列:- 主要目的:数字电位器 嵌入式:- 已用 IC / 零件:AD5258 主要属性:- 次要属性:- 已供物品:板 相关产品:AD5258BRMZ1-ND - IC POT DGTL I2C1K 64P 10MSOPAD5258BRMZ10-ND - IC POT DGTL I2C 10K 64P 10MSOPAD5258BRMZ100-ND - IC POT DGTL I2C 100K 64P 10MSOPAD5258BRMZ50-ND - IC POT DGTL I2C 50K 64P 10MSOPAD5258BRMZ1-R7-ND - IC POT DGTL I2C 1K 64P 10MSOPAD5258BRMZ10-R7-ND - IC POT DGTL I2C 10K 64P 10MSOPAD5258BRMZ50-R7-ND - IC POT DGTL I2C 50K 64P 10MSOPAD5258BRMZ100-R7-ND - IC POT DGTL I2C 100K 64P 10MSOP |
| DC1561W | 制造商:Aleph America Corporation 功能描述: |
| DC1561W-COM | 制造商:Aleph America Corporation 功能描述: |
| DC1562A-A | 功能描述:BOARD EVAL LTC6990 RoHS:是 类别:编程器，开发系统 >> 评估演示板和套件 系列:TimerBlox® 标准包装:1 系列:- 主要目的:电信，线路接口单元（LIU） 嵌入式:- 已用 IC / 零件:IDT82V2081 主要属性:T1/J1/E1 LIU 次要属性:- 已供物品:板，电源，线缆，CD 其它名称:82EBV2081 |
| DC1562A-B | 功能描述:BOARD EVAL LTC6991 RoHS:是 类别:编程器，开发系统 >> 评估演示板和套件 系列:TimerBlox® 标准包装:1 系列:- 主要目的:电信，线路接口单元（LIU） 嵌入式:- 已用 IC / 零件:IDT82V2081 主要属性:T1/J1/E1 LIU 次要属性:- 已供物品:板，电源，线缆，CD 其它名称:82EBV2081 |
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