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參數資料
| 型號： | LTC4268IDKD-1#PBF |
| 廠商： | Linear Technology |
| 文件頁數： | 30/46頁 |
| 文件大小： | 419K |
| 描述： | IC PD HIGH POWER W/CNTRL 32-DFN |
| 產品培訓模塊： | Power over Ethernet |
| 標準包裝： | 52 |
| 類型： | 以太網供電開關（PoE） |
| 應用： | 遠程外設（工業控制，相機，數據訪問） |
| 內部開關： | 是 |
| 工作溫度： | -40°C ~ 85°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 32-WFDFN 裸露焊盤 |
| 供應商設備封裝： | 32-DFN（7x4）裸露焊盤 |
| 包裝： | 管件 |
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LTC4268-1
30
42681fc
applicaTions inForMaTion
behavioris the most apt to be bistable. Capacitive loads
that exhibit I = V
2
/R behavior are less susceptible.
Secondary Leakage Inductance
Leakage inductance on the secondary forms an inductive
divider on the transformer secondary, reducing the size
of the flyback pulse. This increases the output voltage
target by a similar percentage. Note that unlike leakage
spike behavior; this phenomenon is independent of load.
Since the secondary leakage inductance is a constant
percentage of mutual inductance (within manufacturing
variations), the solution is to adjust the feedback resistive
divider ratio to compensate.
Winding Resistance Effects
Primary or secondary winding resistance acts to reduce
overall efficiency (P
OUT
/P
IN
). Secondary winding resistance
increases effective output impedance, degrading load
regulation. Load compensation can mitigate this to some
extent but a good design keeps parasitic resistances low.
Bifilar Winding
A bifilar or similar winding is a good way to minimize
troublesome leakage inductances. Bifilar windings also
improve coupling coefficients and thus improve cross
regulation in multiple winding transformers. However,
tight coupling usually increases primary-to-secondary
capacitance and limits the primary-to-secondary
breakdown voltage, so it isnt always practical.
Primary Inductance
The transformer primary inductance, L
P
, is selected
based on the peak-to-peak ripple current ratio (X) in the
transformer relative to its maximum value.
As a general rule, keep X in the range of 20% to 40%
(i.e., X = 0.2 to 0.4). 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
f
OSC
X
MAX
P
IN
=
V
IN(MAX)
DC
MIN
(
)
2
Eff
f
OSC
X
MAX
P
OUT
where:
f
OSC
is the oscillator frequency
DC
MIN
is the DC at maximum input voltage
X
MAX
is ripple current ratio at maximum input voltage
Using common high power PoE values a 48V (41V < V
IN
< 57V) to 5V/5.3A Converter with 90% efficiency, P
OUT
=
26.5W and P
IN
= 29.5W Using X = 0.4 N = 1/8 and f
OSC
= 200kHz:
DC
MIN
=
1
1+
N V
IN(MAX)
V
OUT
=
1
1+
1
8
57
5
= 41.2%
L
P
=
57V 0.412
(
)
2
2 kHz .4 2 . W
=260礖
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 trade-offs.
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LTC4268IDKD-1-TR | 制造商:LINER 制造商全稱:Linear Technology 功能描述:High Power PD with Synchronous NoOpto Flyback Controller |
| LTC4268IDKD-1-TRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:High Power PD with Synchronous NoOpto Flyback Controller |
| LTC4269-1 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:IEEE 802.3at PD with Synchronous No-Opto Flyback Controller |
| LTC4269-2 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:IEEE 802.3at High Power PD and Synchronous Forward Controller with AUX Support |
| LTC4269CDKD-1#PBF | 功能描述:IC PD/OPTO FLYBACK CTRLR 32-DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 熱交換 系列:- 標準包裝:50 系列:- 類型:熱交換控制器 應用:-48V 遠程電力系統，AdvancedTCA ? 系統，高可用性 內部開關:無 電流限制:可調 電源電壓:11.5 V ~ 14.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬） 供應商設備封裝:10-MSOP 包裝:管件 |
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