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參數(shù)資料
| 型號： | ISL6721ABZ |
| 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 44-PLCC 0 to 70 |
| 中文描述： | 1 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | 0.150 INCH, ROHS COMPLIANT, PLASTIC, MS-012AC, SOIC-16 |
| 文件頁數(shù)： | 14/20頁 |
| 文件大?。?/td> | 481K |
| 代理商： | ISL6721ABZ |
14
The final component of MOSFET loss is caused by the
charging of the gate capacitance through the device gate
resistance. Depending on the relative value of any external
resistance in the gate drive circuit, a portion of this power will
be dissipated externally.
Once the losses are known, the device package must be
selected and the heatsinking method designed. Since the
design requires a small surface mount part, a SOIC-8
package was selected. A Fairchild FDS2570 MOSFET was
selected based on these criteria. The overall losses are
estimated at 400mW.
Output Filter Design
In a flyback design, the primary concern for the design of the
output filter is the capacitor ripple current stress and the
ripple and noise specification of the output.
The current flowing in and out of the output capacitors is the
difference between the winding current and the output
current. The peak secondary current, Ispk, is 10.73A for the
3.3V output and 4.29A for the 1.8V output. The current
flowing into the output filter capacitor is the difference
between the winding current and the output current. Looking
at the 3.3V output, the peak winding current is Ispk =
10.73A. The capacitor must store this amount minus the
output current of 2.5A, or 8.23A. The RMS ripple current in
the 3.3V output capacitor is about 3.5 Arms. The RMS ripple
current in the 1.8V output capacitor is about 1.4 Arms
Voltage deviation on the output during the switching cycle
(ripple and noise) is caused by the change in charge of the
output capacitance, the equivalent series resistance (ESR),
and equivalent series inductance (ESL). Each of these
components must be assigned a portion of the total ripple
and noise specification. How much to allow for each
contributor is dependent on the capacitor technology used.
For purposes of this discussion we will assume the following:
3.3V output: 100mV total output ripple and noise
ESR: 60mV
Capacitor
Q: 10mV
ESL: 30mV
1.8V output: 50mV total output ripple and noise
ESR: 30mV
Capacitor
Q: 5mV
ESL: 15mV
For the 3.3V output:
The change in voltage due to the change in charge of the
output capacitor,
Q, determines how much capacitance is
required on the output.
ESL adds to the ripple and noise voltage in proportion to the
rate of change of current into the capacitor (V = L
di/dt).
Capacitors having high capacitance usually do not have
sufficiently low ESL. High frequency capacitors such as
surface mount ceramic or film are connected in parallel with
the high capacitance capacitors to address the effects of
ESL. A combination of high frequency and high ripple
capability capacitors is used to achieve the desired overall
performance. The analysis of the 1.8V output is similar to
that of the 3.3V output and is omitted for brevity. Two
OSCON 4SEP560M (560
μ
F) electrolytic capacitors and a
22
μ
F X5R ceramic 1210 capacitor were selected for both the
3.3 and 1.8V outputs. The 4SEP560M electrolytic capacitors
are each rated at 4520mA ripple current and 13m
of ESR.
The ripple current rating of just one of these capacitors is
adequate, but two are needed to meet the minimum ESR
and capacitance values.
The bias output is of such low power and current that it
places negligible stress on its filter capacitor. A single 0.1
μ
F
ceramic capacitor was selected.
Control Loop Design
The major components of the feedback control loop are a
programmable shunt regulator, an opto-coupler, and the
inverting amplifier of the ISL6721. The opto-coupler is used
to transfer the error signal across the isolation barrier. The
opto-coupler offers a convenient means to cross the isolation
barrier, but it adds complexity to the feedback control loop. It
adds a pole at about 10kHz and a significant amount of gain
variation due the current transfer ratio (CTR). The CTR of
the opto-coupler varies with initial tolerance, temperature,
forward current, and age.
Pgate
Qg
Vg
Fsw
=
W
(EQ. 22)
ESR
–
Ispk
Iout
-----------------------------
≤
–
----------------------------
7.3m
=
=
(EQ. 23)
C
---------------–
(
)
Tr
2
≥
-------------------–
(
)
2.33
6
–
×
10
0.010
960
μ
F
=
=
(EQ. 24)
L
--------------
≤
---------------------------------10
9
–
0.56nH
=
=
(EQ. 25)
ISL6721
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| ISL6721AV | 1024 x 9 x 2 Asynchronous Bidirectional FIFO Memory 64-TQFP 0 to 70 |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ISL6721ABZ-T | 功能描述:IC REG CTRLR PWM CM 16-SOIC 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) |
| ISL6721AV | 功能描述:IC REG CTRLR PWM CM 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) |
| 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) |
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