參數(shù)資料
型號: MAX5015
廠商: Maxim Integrated Products, Inc.
元件分類: 外設(shè)及接口
英文描述: Low Power 5V RS232 Dual Driver/Receiver with 0.1?μF Capacitors; Package: SO; No of Pins: 16; Temperature Range: -40?°C to 85?°C
中文描述: 電可擦除可編程邏輯器件
文件頁數(shù): 11/14頁
文件大?。?/td> 319K
代理商: MAX5015
where V
REF
is the reference voltage of the shunt
regulator, and R
1
and R
2
are the resistors shown in
Figures 2 and 3.
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 MAX5015 (44%). To
enable the use of MOSFETs with drain-source
breakdown voltages of less than 200V use the
MAX5015 with the 50% maximum duty cycle.
Calculate the turns ratio according to the following
equation:
where:
N
S
/N
P
= Turns ratio (N
S
is the number of secondary
turns and N
P
is the number of primary turns).
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 (36V).
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
= 5.
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 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 (D
MIN
) use the
following equation:
V
N
N
P
=
where V
IN_MAX
is the maximum input voltage (72V).
4) The reset winding turns ratio (N
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
) will
determine 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 mini-
mum operating voltage at V
DD
(13V). Use the follow-
V
7
1 + 14
14
DSMAX
×
=
2
144
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
-V
MIN
OUT
×
IN_MAX
S
D1
=
=
19 8
N
N
5V+ 0.5V
0 44 36
.
0.44
V
S
P
×
)
=
0 330
.
N
N
V
V
×
D
D
V
S
P
OUT
D1
MAX
MAX
IN_MIN
+
×
(
)
V
V
R
+
R
R
REF
OUT
2
1
2
=
M
Current-Mode PWM Controllers with Integrated
Startup Circuit for Isolated Power Supplies
______________________________________________________________________________________
11
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MAX5015CSA 功能描述:電流型 PWM 控制器 w/Integrated Startup RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
MAX5015CSA+ 功能描述:電流型 PWM 控制器 w/Integrated Startup RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
MAX5015CSA+T 功能描述:電流型 PWM 控制器 w/Integrated Startup RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
MAX5015CSA-T 功能描述:電流型 PWM 控制器 w/Integrated Startup RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
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