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參數(shù)資料
| 型號： | ISL6740IV |
| 廠商： | INTERSIL CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Octal Buffers/Drivers With 3-State Outputs 20-SSOP -40 to 85 |
| 中文描述： | 0.5 A SWITCHING CONTROLLER, 2000 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | PLASTIC, MO-153-AB, TSSOP-16 |
| 文件頁數(shù)： | 16/29頁 |
| 文件大小： | 639K |
| 代理商： | ISL6740IV |
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16
allowable power dissipation in the ferrite material and is
influenced by the lossiness of the core, core geometry,
operating ambient temperature, and air flow. The TDK
datasheet for PC44 material indicates a core loss factor of
~400 mW/cm
3
with a ± 2000 gauss 100kHz sinusoidal
excitation. The application uses a 235kHz square wave
excitation, so no direct comparison between the application
and the data can be made. Interpolation of the data is
required. The core volume is approximately 1.6cm
3
, so the
estimated core loss is
1.28W of dissipation is significant for a core of this size.
Reducing the flux density to 1200 gauss will reduce the
dissipation by about the same percentage, or 40%.
Ultimately, evaluation of the transformer’s performance in the
application will determine what is acceptable.
From Faraday’s Law and using 1200 gauss peak flux density
(
B = 2400 gauss or 0.24 tesla)
Rounding up yields 4 turns for the primary winding. The
peak flux density using 4 turns is ~1100 gauss. From EQ. 1,
the number of secondary turns is 2.
The volts/turn for this design ranges from 5.4V at V
IN
= 43V
to 6.6V at V
IN
= 53V. Therefore, the synchronous rectifier
(SR) windings may be set at 1 turn each with proper FET
selection. Selecting 2 turns for the synchronous rectifier
windings would also be acceptable, but the gate drive losses
would increase.
The next step is to determine the equivalent wire gauge for
the planar structure. Since each secondary winding
conducts for only 50% of the period, the RMS current is
where D is the duty cycle. Since an FR-4 PWB planar
winding structure was selected, the width of the copper
traces is limited by the window area width, and the number
of layers is limited by the window area height. The PQ core
selected has a usable window area width of 0.165 inches.
Allowing one turn per layer and 0.020 inches clearance at
the edges allows a maximum trace width of 0.125 inches.
Using 100 circular mils(c.m.)/A as a guideline for current
density, and from EQ. 17, 707c.m. are required for each of
the secondary windings (a circular mil is the area of a circle
0.001 inches in diameter). Converting c.m. to square mils
yields 555mils
2
(0.785 sq. mils/c.m.). Dividing by the trace
width results in a copper thickness of 4.44mils (0.112mm).
Using 1.3mils/oz. of copper requires a copper weight of
3.4oz. For reasons of cost, 3oz. copper was selected.
One layer of each secondary winding also contains the
synchronous rectifier winding. For this layer the secondary
trace width is reduced by 0.025 inches to 0.100 inches(0.015
inches for the SR winding trace width and 0.010 inches
spacing between the SR winding and the secondary
winding).
The choice of copper weight may be validated by calculating
the DC copper losses of the secondary winding as follows.
Ignoring the terminal and lead-in resistance, the resistance
of each layer of the secondary may be approximated using
EQ. 18.
where
R = Winding resistance
ρ
= Resistivity of copper = 669e-9
-inches at 20°C
t = Thickness of the copper (3 oz.) = 3.9e-3 inches
r
2
= Outside radius of the copper trace = 0.324 or 0.299
inches
r
1
= Inside radius of the copper trace = 0.199 inches
The winding without the SR winding on the same layer has a
DC resistance 2.21m
. The winding that shares the layer
with the SR winding has a DC resistance of 2.65m
. With
the secondary configured as a 4 turn center tapped winding
(2 turns each side of the tap), the total DC power loss for the
secondary at 20°C is 486mW.
The primary windings have an RMS current of approximately
5 A (I
OUT
x N
S
/N
P
at ~ 100% duty cycle). The primary is
configured as 2 layers, 2 turns per layer to minimize the
winding stack height. Allowing 0.020 inches edge clearance
and 0.010 inches between turns yields a trace width of
0.0575 inches. Ignoring the terminal and lead-in resistance,
and using EQ. 18, the inner trace has a resistance of
4.25m
, and the outer trace has a resistance of 5.52m
.
The resistance of the primary then is 19.5m
at 20°C. The
total DC power loss for the secondary at 20°C is 489mW.
Improved efficiency and thermal performance could be
achieved by selecting heavier copper weight for the
windings. Evaluation in the application will determine its
need.
P
loss
cm
3
-----------
cm
3
f
meas
---------------
0.4
1.6
---------------------
1.28
=
=
≈
W
(EQ. 15)
N
V
T
B
e
-----------------------------
6
–
2
6.2
10
0.24
----------------------------------------------------
3.56
=
=
=
turns
(EQ. 16)
I
RMS
I
OUT
D
10
0.5
7.07
=
=
=
A
(EQ. 17)
R
t
2
r
1
----
ln
-----------------------
=
(EQ. 18)
ISL6740, ISL6741
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| ISL6741 | Flexible Double Ended Voltage and Current Mode PWM Controllers(靈活的雙端電壓和電流模式PWM控制器) |
| ISL6845IB | Improved Industry Standard Single Ended Current Mode PWM Controller |
| ISL6845 | Improved Industry Standard Single Ended Current Mode PWM Controller |
| ISL6845IRZ-T | Improved Industry Standard Single-Ended Current Mode PWM Controller |
| ISL6845IU | Octal Buffers/Drivers With 3-State Outputs 20-SO -40 to 85 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ISL6740IV-T | 功能描述:IC REG CTRLR PWM VM 16-TSSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:100% 電源電壓:8.2 V ~ 30 V 降壓:無 升壓:無 回掃:是 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:是 工作溫度:0°C ~ 70°C 封裝/外殼:8-DIP（0.300"，7.62mm） 包裝:管件 產(chǎn)品目錄頁面:1316 (CN2011-ZH PDF) |
| ISL6740IVZ | 功能描述:電壓模式 PWM 控制器 VOLT PWM MODE CONTRL 16LD TSSOP RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| ISL6740IVZ-T | 功能描述:IC REG CTRLR PWM VM 16-TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:275kHz 占空比:50% 電源電壓:18 V ~ 110 V 降壓:無 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:是 工作溫度:-40°C ~ 85°C 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) |
| ISL6741IB | 功能描述:電流型 PWM 控制器 CUR PWM MODE CNTRLR 16LD N RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)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 |
| ISL6741IB-T | 功能描述:IC REG CTRLR PWM CM 16-SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:100% 電源電壓:8.2 V ~ 30 V 降壓:無 升壓:無 回掃:是 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:是 工作溫度:0°C ~ 70°C 封裝/外殼:8-DIP（0.300"，7.62mm） 包裝:管件 產(chǎn)品目錄頁面:1316 (CN2011-ZH PDF) |
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