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參數(shù)資料
| 型號： | ISL6539IA-T |
| 廠商： | INTERSIL CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Circular Connector; No. of Contacts:29; Series:D38999; Body Material:Metal; Connecting Termination:Crimp; Connector Shell Size:25; Circular Contact Gender:Socket; Circular Shell Style:Straight Plug; Insert Arrangement:25-29 |
| 中文描述： | DUAL SWITCHING CONTROLLER, 345 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封裝： | PLASTIC, QSOP-28 |
| 文件頁數(shù)： | 16/20頁 |
| 文件大小： | 503K |
| 代理商： | ISL6539IA-T |
16
FN9144.4
June 6, 2005
The inductor copper loss can be significant in the total
system power loss. Attention has to be given to the DCR
selection. Another factor to consider when choosing the
inductor is its saturation characteristics at elevated
temperature. Saturated inductors could result in nuisance
OC, or OV trip.
Output voltage ripple and the transient voltage deviation are
factors that have to be taken into consideration when
selecting an output capacitor. In addition to high frequency
noise related MOSFET turn-on and turn-off, the output
voltage ripple includes the capacitance voltage drop and
ESR voltage drop caused by the AC peak-to-peak current.
These two voltages can be represented by:
These two components constitute a large portion of the total
output voltage ripple. Several capacitors have to be
paralleled in order to reduce the ESR and the voltage ripple.
If the output of the converter has to support another load
with high pulsating current, such as the first channel in
Figure 2, it feeds into the VTT channel which draws high
pulsating current. More capacitors are needed in order to
reduce the equivalent ESR and suppress the voltage ripple
to a tolerable level.
To support a load transient that is faster than the switching
frequency, more capacitors have to be used to reduce the
voltage excursion during load step change. Another aspect
of the capacitor selection is that the total AC current going
through the capacitors has to be less than the rated RMS
current specified on the capacitors, to prevent the capacitor
from overheating.
For DDR applications, as the second channel draws pulsate
current directly from the first channel, it is recommended to
parallel capacitors for output of the first channel to reduce
ESR and smooth ripple. Excessive high ripple voltage at the
output can propagate into the output of the error amplifier
and cause too much phase voltage jitter.
Input Capacitor Selection
The important parameters for the bulk input capacitance are
the voltage rating and the RMS current rating. For reliable
operation, select bulk capacitors with voltage and current
ratings above the maximum input voltage and largest RMS
current required by the circuit. Their voltage rating should be
at least 1.25 times greater than the maximum input voltage,
while a voltage rating of 1.5 times is a conservative
guideline. For most cases, the RMS current rating
requirement for the input capacitor of a buck regulator is
approximately 1/2 the DC load current.
The maximum RMS current required by the regulator may be
closely approximated through the following equation:
In addition to the bulk capacitance, some low ESL ceramic
decoupling is recommended to be used between the drain
terminal of the upper MOSFET and the source terminal of
the lower MOSFET, in order to clamp the parasitic voltage
ringing at the phase node in switching.
Choosing MOSFETs
For a maximum input voltage of 15V, at least a minimum 30V
MOSFETs should be used. The design has to trade off the
gate charge with the r
DSON
of the MOSFET:
For the lower MOSFET, before it is turned on, the body
diode has been conducting. The lower MOSFET driver will
not charge the miller capacitor of this MOSFET.
In the turning off process of the lower MOSFET, the load
current will shift to the body diode first. The high dv/dt of
the phase node voltage will charge the miller capacitor
through the lower MOSFET driver sinking current path.
This results in much less switching loss of the lower
MOSFETs.
The duty cycle is often very small in high battery voltage
applications, and the lower MOSFET will conduct most of
the switching cycle; therefore, the lower the r
DSON
of the
lower MOSFET, the less the power loss. The gate charge for
this MOSFET is usually of secondary consideration.
The upper MOSFET does not have this zero voltage
switching condition, and because the upper MOSFET
conducts for less time compared to the lower MOSFET, the
switching loss tends to be dominant. Priority should be given
to the MOSFETs with less gate charge, so that both the gate
driver loss, and switching loss, will be minimized.
For the lower MOSFET, its power loss can be assumed to be
the conduction loss only.
For the upper MOSFET, its conduction loss can be written as:
and its switching loss can be written as:
The peak and valley current of the inductor can be obtained
based on the inductor peak-to-peak current and the load
current. The turn-on and turn-off time can be estimated with
the given gate driver parameters in the Electrical
V
c
I
8CF
sw
------------------
=
V
esr
I
pp
ESR
=
ICin RMS
(
)
IOUT
2
D
D2
–
(
)
IRipple p
p
–
(
)
2
D
12
------
+
=
P
lower
V
IN
(
)
1
D V
IN
)
–
(
)
I
load
r
2
DS ON
)
Lower
≈
P
uppercond
V
IN
(
)
D V
IN
)
I
load
r
2
DS ON
)
upper
=
P
uppersw
V
IN
(
)
V
I
T
F
2
---------------------------------------------
V
I
T
F
2
----------------------------------------------
+
=
ISL6539
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| ISL6539IAZ | 功能描述:電流型 PWM 控制器 ISL6539 DL SWITCHER 15V INDUSTRIAL GRD 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 |
| ISL6539IAZ-T | 功能描述:電流型 PWM 控制器 ISL6539 DL SWITCHER 15V INDUSTRIAL GRD 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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| ISL6540ACRZ-T | 功能描述:IC REG CTRLR BUCK PWM VM 28-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 特色產(chǎn)品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標(biāo)準(zhǔn)包裝:1 系列:PowerWise® PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:81% 電源電壓:4.5 V ~ 18 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-5°C ~ 125°C 封裝/外殼:32-WFQFN 裸露焊盤 包裝:Digi-Reel® 產(chǎn)品目錄頁面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR |
| ISL6540ACRZ-TR5453 | 制造商:Intersil Corporation 功能描述:STD. ISL6540ACRZ-T W/GOLD BOND WIRE ONLY - Tape and Reel |
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