參數(shù)資料
型號： MAX5942ACSE
廠商： MAXIM INTEGRATED PRODUCTS INC
元件分類： 穩(wěn)壓器
英文描述： IEEE 802.3af Power-Over-Ethernet Interface/PWM Controller for Power Devices
中文描述： 1 A SWITCHING CONTROLLER, 314 kHz SWITCHING FREQ-MAX, PDSO16
封裝： 0.150 INCH, MS-012AC, SOIC-16
文件頁數(shù)： 19/24頁
文件大?。?/td> 465K
代理商： MAX5942ACSE
M
IEEE 802.3af Power-Over-Ethernet
Interface/PWM Controller for Power Devices
______________________________________________________________________________________
19
V
OUT
= Output voltage (5V).
V
D1
= Voltage drop across D1 (typically 0.5V for
power Schottky diodes).
D
MAX
= Minimum value of maximum operating duty
cycle (44%).
V
IN_MIN
= Minimum input voltage (30V).
In this example:
Choose N
P
based on core losses and DC resis-
tance. Use the turns ratio to calculate N
S
, rounding
up to the nearest integer. In this example, N
P
= 14
and N
S
= 6.
For a forward converter, choose a transformer with a
magnetizing inductance in the neighborhood of
200μH. Energy stored in the magnetizing inductance
of a forward converter is not delivered to the load
and must be returned back to the input; this is
accomplished with the reset winding.
The transformer primary to secondary leakage
inductance should be less than 1μH. Note that all
leakage energy is dissipated across the MOSFET.
Snubber circuits may be used to direct some or all
of the leakage energy to be dissipated across a
resistor.
To calculate the minimum duty cycle (D
MIN
), use the
following equation:
V
MIN
=
=
where V
IN_MAX
is the maximum input voltage (67V).
R
/N
P
) needs to be
low enough to guarantee that the entire energy in
the transformer is returned to V+ within the off cycle
at the maximum duty cycle. Use the following equa-
tion to determine the reset winding turns ratio:
where:
N
R
/N
P
= Reset winding turns ratio.
D
MAX
’
= Maximum value of maximum duty cycle:
Round N
R
to the nearest smallest integer.
The turns ratio of the reset winding (N
R
/N
P
) determines
the peak voltage across the N-channel MOSFET.
Use the following equation to determine the maxi-
mum drain-source voltage across the N-channel
MOSFET:
V
DSMAX
= Maximum MOSFET drain-source voltage.
V
IN_MAX
= Maximum input voltage:
Choose MOSFETs with appropriate avalanche
power ratings to absorb any leakage energy.
5) Choose the tertiary winding turns ratio (N
T
/N
P
) so that
the minimum input voltage provides the minimum
operating voltage at V
DD
(13V). Use the following
equation to calculate the tertiary winding turns ratio:
where:
V
DDMIN
is the minimum V
DD
supply voltage (13V).
V
DDMAX
is the maximum V
DD
supply voltage (30V).
V
IN_MIN
is the minimum input supply voltage (30V).
V
IN_MAX
is the maximum input supply voltage (67V
in this design example).
N
P
is the number of turns of the primary winding.
N
T
is the number of turns of the tertiary winding:
Choose N
T
= 7.
13 7
30
4
36 7
67
14
6 39
.
7 67
.
.
.
1
N
N
T
T
×
≤
≤
×
≤
≤
V
V
N
N
V
V
N
DDMIN
IN_MIN
P
T
DDMAX
IN_MAX
P
+
×
≤
≤
+
×
0 7
.
0 7
.
V
1 + 14
14
DSMAX
≥
×
=
67
134
V
V
V
V
1 + N
N
DSMAX
IN_MAX
P
R
≥
×
N
1
1-0.5
0.5
R
≤
×
=
4
14
N
N
1-D
D
R
P
MAX
MAX
≤
×
′
′
D
V
N
N
-V
OUT
IN_MAX
S
P
D1
×
N
N
5V+ 0.5V
0 44 30
.
0.44
V
S
P
≥
×
)
=
0 395
.
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX5942ACSE+ 功能描述:輸入/輸出控制器接口集成電路 IEEE 802.3af POE Int/PWM Controller RoHS:否 制造商:Silicon Labs 產(chǎn)品: 輸入/輸出端數(shù)量: 工作電源電壓: 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-64 封裝:Tray
MAX5942ACSE+T 功能描述:輸入/輸出控制器接口集成電路 IEEE 802.3af POE Int/PWM Controller RoHS:否 制造商:Silicon Labs 產(chǎn)品: 輸入/輸出端數(shù)量: 工作電源電壓: 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-64 封裝:Tray
MAX5942ACSE-T 功能描述:電源開關(guān) IC - POE / LAN RoHS:否 制造商:Fairchild Semiconductor 開關(guān)數(shù)量:Single 開關(guān)配置:SPST 開啟電阻（最大值）:7.3 Ohms 串話: 帶寬: 開啟時間（最大值）:13 ns 關(guān)閉時間（最大值）:20 ns 切換電壓（最大）: 工作電源電壓:8 V to 26 V 最大工作溫度:+ 125 C 安裝風(fēng)格:Through Hole 封裝 / 箱體:TO-220F-6
MAX5942AESE 功能描述:電源開關(guān) IC - POE / LAN RoHS:否 制造商:Fairchild Semiconductor 開關(guān)數(shù)量:Single 開關(guān)配置:SPST 開啟電阻（最大值）:7.3 Ohms 串話: 帶寬: 開啟時間（最大值）:13 ns 關(guān)閉時間（最大值）:20 ns 切換電壓（最大）: 工作電源電壓:8 V to 26 V 最大工作溫度:+ 125 C 安裝風(fēng)格:Through Hole 封裝 / 箱體:TO-220F-6
MAX5942AESE+ 功能描述:輸入/輸出控制器接口集成電路 IEEE 802.3af POE Int/PWM Controller RoHS:否 制造商:Silicon Labs 產(chǎn)品: 輸入/輸出端數(shù)量: 工作電源電壓: 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-64 封裝:Tray
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