參數(shù)資料
型號(hào)： MAX5941ACSE+T
廠商： Maxim Integrated Products
文件頁(yè)數(shù)： 10/24頁(yè)
文件大?。?/td> 0K
描述： IC IEEE 802.3AF-COMP POE 16-SOIC
產(chǎn)品培訓(xùn)模塊： Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
標(biāo)準(zhǔn)包裝： 2,500
控制器類型： 以太網(wǎng)供電控制器（POE）
接口： IEEE 802.3af
電源電壓： 48V
電流 - 電源： 1mA
工作溫度： 0°C ~ 70°C
安裝類型： 表面貼裝
封裝/外殼： 16-SOIC（0.154"，3.90mm 寬）
供應(yīng)商設(shè)備封裝： 16-SOIC
包裝： 帶卷 (TR)
MAX5941A/MAX5941B
IEEE 802.3af-Compliant Power-Over-Ethernet
Interface/PWM Controller for Power Devices
18
______________________________________________________________________________________
where k = 0.75 to 1, and NS and NP are the number of
turns on the secondary and primary side of the trans-
former, respectively. L is the output filter inductor. This
makes the output inductor current downslope as refer-
enced across RSENSE equal to the slope compensa-
tion. The controller responds to transients within one
cycle when this condition is met.
N-Channel MOSFET Gate Driver
NDRV drives an N-channel MOSFET. NDRV sources
and sinks large transient currents to charge and dis-
charge the MOSFET gate. To support such switching
transients, bypass VCC with a ceramic capacitor. The
average current as a result of switching the MOSFET is
the product of the total gate charge and the operating
frequency. It is this current plus the DC quiescent cur-
rent that determines the total operating current.
Applications Information
Design Example
The following is a general procedure for designing a
forward converter (Figure 5) using the MAX5941B:
1) Determine the requirements.
2) Set the output voltage.
3) Calculate the transformer primary to secondary
winding turns ratio.
4) Calculate the reset to primary winding turns ratio.
5) Calculate the tertiary to primary winding turns
ratio.
6) Calculate the current-sense resistor value.
7) Calculate the output inductor value.
8) Select the output capacitor.
The circuit in Figure 5 was designed as follows:
1) 30V
≤ VIN ≤ 67V, VOUT = 5V, IOUT = 10A, VRIPPLE ≤
50mV. Turn-on threshold is set at 38.6V.
2) To set the output voltage, calculate the values of
resistors R1 and R2 according to the following
equation:
where VREF is the reference voltage of the shunt
regulator, and R1 and R2 are the resistors shown in
Figures 5 and 6.
3) The turns ratio of the transformer is calculated based
on the minimum input voltage and the lower limit of
the maximum duty cycle for the MAX5941B (44%).
To enable the use of MOSFETs with drain-source
breakdown voltages of less than 200V, use the
MAX5941B with the 50% maximum duty cycle.
Calculate the turns ratio according to the following
equation:
where:
NS/NP = Turns ratio (NS is the number of secondary
turns and NP is the number of primary turns).
VOUT = Output voltage (5V).
VD1 = Voltage drop across D1 (typically 0.5V for
power Schottky diodes).
DMAX = Minimum value of maximum operating duty
cycle (44%).
VIN_MIN = Minimum Input voltage (30V).
In this example:
Choose NP based on core losses and DC resis-
tance. Use the turns ratio to calculate NS, rounding
up to the nearest integer. In this example, NP = 14
and NS = 6.
For a forward converter, choose a transformer with a
magnetizing inductance in the neighborhood of
200H. 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 1H. Note that all
leakage energy will be dissipated across the MOS-
FET. 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 (DMIN), use the
following equation:
=
where VIN_MAX is the maximum input voltage (67V).
D
V
N
-V
MIN
OUT
IN_MAX
S
P
D1
=
×
=17 7
.
N
5V + 0.5V 0.44
S
P
≥
×
()
×
=
044 30
0 395
.
V
N
VV
D
DV
S
P
OUT
D1
MAX
IN_MIN
≥
+×
()
×
V
R
RR
REF
OUT
2
12
=
+
N
kR
V
S
P
SENSE
OUT
× ××
=
L
mV
s
26
/
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參數(shù)描述
MAX5941AESE 功能描述:電源開(kāi)關(guān) IC - POE / LAN RoHS:否 制造商:Fairchild Semiconductor 開(kāi)關(guān)數(shù)量:Single 開(kāi)關(guān)配置:SPST 開(kāi)啟電阻（最大值）:7.3 Ohms 串話: 帶寬: 開(kāi)啟時(shí)間（最大值）:13 ns 關(guān)閉時(shí)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
MAX5941AESE+ 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
MAX5941AESE+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
MAX5941AESE-T 功能描述:電源開(kāi)關(guān) IC - POE / LAN RoHS:否 制造商:Fairchild Semiconductor 開(kāi)關(guān)數(shù)量:Single 開(kāi)關(guān)配置:SPST 開(kāi)啟電阻（最大值）:7.3 Ohms 串話: 帶寬: 開(kāi)啟時(shí)間（最大值）:13 ns 關(guān)閉時(shí)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
MAX5941BCSE 功能描述:電源開(kāi)關(guān) IC - POE / LAN RoHS:否 制造商:Fairchild Semiconductor 開(kāi)關(guān)數(shù)量:Single 開(kāi)關(guān)配置:SPST 開(kāi)啟電阻（最大值）:7.3 Ohms 串話: 帶寬: 開(kāi)啟時(shí)間（最大值）:13 ns 關(guān)閉時(shí)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
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