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參數(shù)資料
| 型號： | ISL6721AV |
| 廠商： | INTERSIL CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 1024 x 9 x 2 Asynchronous Bidirectional FIFO Memory 64-TQFP 0 to 70 |
| 中文描述： | 1 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | 4.40 MM, PLASTIC, MO-153AB, TSSOP-16 |
| 文件頁數(shù)： | 12/20頁 |
| 文件大?。?/td> | 481K |
| 代理商： | ISL6721AV |
12
Peak Primary Current:
Maximum Primary Inductance:
Choose desired primary inductance to be 40
μ
H.
The core structure must be able to deliver a certain amount
of energy to the secondary on each switching cycle in order
to maintain the specified output power.
where
w is the amount of energy required to be transferred
each cycle and Vd is the drop across the output rectifier.
The capacity of a gapped ferrite core structure to store
energy is dependent on the volume of the airgap and can be
expressed as:
where Aeff is the effective cross sectional area of the core in
m
2
, lg is the length of the airgap in meters,
μ
o
is the
permeability of free space (4
π
10
-7
), and
B is the change
in flux density in Tesla.
A core structure having less airgap volume than calculated
will be incapable of providing the full output power over some
portion of its operating range. On the other hand, if the
length of the airgap becomes large, magnetic field fringing
around the gap occurs. This has the effect of increasing the
airgap volume. Some fringing is usually acceptable, but
excessive fringing can cause increased losses in the
windings around the gap resulting in excessive heating.
Once a suitable core and gap combination are found, the
iterative design cycle begins. A design is developed and
checked for ease of assembly and thermal performance. If
the core does not allow adequate space for the windings,
then a core with a larger window area is required. If the
transformer runs hot, it may be necessary to lower the flux
density (more primary turns, lower operating frequency),
select a less lossy core material, change the geometry of the
windings (winding order), use heavier gauge wire or multi-
filar windings, and/or change the type of wire used (Litz wire,
for example).
For simplicity, only the final design is further described.
An EPCOS EFD 20/10/7 core using N87 material gapped to
an A
L
value of 25 nH/N
2
was chosen. It has more than the
required air gap volume to store the energy required, but was
needed for the window area it provides.
Aeff = 31
10
-6
m
2
lg = 1.56
10
-3
m
The flux density
B is only 0.069T or 690 gauss, a relatively
low value.
Since
the number of primary turns, N
p
, may be calculated. The
result is N
p
= 40 turns. The secondary turns may be
calculated as follows:
where Tr is the time required to reset the core. Since
discontinuous MMF mode operation is desired, the core
must completely reset during the off time. To maintain
discontinuous mode operation, the maximum time allowed to
reset the core is Tsw - Ton(max) where Tsw = 1/Fsw. The
minimum time is application dependent and at the designers
discretion knowing that the secondary winding RMS current
and ripple current stress in the output capacitors increases
with decreasing reset time. The calculation for maximum N
s
for the 3.3 V output using T = Tsw - Ton (max) = 2.75
μ
S is
5.52 turns.
The determination of the number of secondary turns is also
dependent on the number of outputs and the required turns
ratios required to generate them. If schottky output rectifiers
are used and we assume a forward voltage drop of 0.45V,
the required turns ratio for the two output voltages, 3.3V and
1.8V, is 5:3.
With a turns ratio of 5:3 for the secondary windings, we will
use N
s1
= 5 turns and N
s2
= 3 turns. Checking the reset time
using these values for the number of secondary turns yields
a duration of Tr = 2.33
μ
S or about 47% of the switching
period, an acceptable result.
The bias winding turns may be calculated similarly, only a
diode forward drop of 0.7V is used. The rounded off result is
17 turns for a 12V bias.
The next step is to determine the wire gauge. The RMS
current in the primary winding may be calculated from:
The peak and RMS current values in the remaining windings
may be calculated from:
Ippk
(
)
---------------------------------------------
1.87
=
=
A
(EQ. 9)
Lp max
(
)
-----------------------------------------------------------
)
43.3
=
=
μ
H
(EQ. 10)
w
Pout
Vout
-------------------+
=
joules
(EQ. 11)
Vg
Aeff
lg
2
-----------------------------
μ
B
w
=
=
m
3
(EQ. 12)
L
p
μ
----------------------------------------
N
2
Aeff
=
μ
H
(EQ. 13)
N
s
p
o
Tr
Aeff
------------------------------+
≤
(EQ. 14)
Ip rms
(
)
Ippk
)
----------------------------
=
A
(EQ. 15)
Ispk
-------------------------------------
Tr
=
A
(EQ. 16)
Irms
2
Iout
3
Tr
--------------
=
A
(EQ. 17)
ISL6721
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ISL6721AV-T | 功能描述:電流型 PWM 控制器 FLEXIBLE SINGLE END CUR MODE PWM 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 |
| ISL6721AVZ | 功能描述:電流型 PWM 控制器 FLEX SNG ENDED CUR MODE PWM CONTRLR 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 |
| ISL6721AVZ-T | 功能描述:IC REG CTRLR PWM CM 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) |
| ISL6721EVAL1 | 功能描述:EVALUATION BOARD ISL6721 RoHS:否 類別:RF/IF 和 RFID >> RF 評估和開發(fā)套件，板 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 類型:GPS 接收器 頻率:1575MHz 適用于相關(guān)產(chǎn)品:- 已供物品:模塊 其它名稱:SER3796 |
| ISL6721EVAL3Z | 功能描述:EVAL BOARD 3 FOR ISL6721 RoHS:是 類別:編程器，開發(fā)系統(tǒng) >> 評估板 - DC/DC 與 AC/DC（離線）SMPS 系列:* 產(chǎn)品培訓(xùn)模塊:Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:1 系列:True Shutdown™ 主要目的:DC/DC，步升 輸出及類型:1，非隔離 功率 - 輸出:- 輸出電壓:- 電流 - 輸出:1A 輸入電壓:2.5 V ~ 5.5 V 穩(wěn)壓器拓?fù)浣Y(jié)構(gòu):升壓 頻率 - 開關(guān):3MHz 板類型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
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