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| 型號： | SP6132 |
| 英文描述： | Wide Input, 300KHz Synchronous PWM Controller |
| 中文描述： | 寬輸入，300kHz的同步PWM控制器 |
| 文件頁數(shù)： | 9/14頁 |
| 文件大?。?/td> | 314K |
| 代理商： | SP6132 |
9
Date: 8/4/04
SP6132 Wide Input, 300KHz Synchronous PWM Controller Copyright 2004 Sipex Corporation
APPLICATIONS INFORMATION: Continued
The capacitor type suitable for the output capac-
itors can also be used for the input capacitors.
However, exercise extra caution when tantalum
capacitors are considered. Tantalum capacitors are
known for catastrophic failure when exposed to
surge current, and input capacitors are prone to
such surge current when power supplies are con-
nected “l(fā)ive” to low impedance power sources.
MOSFET Selection
The losses associated with MOSFETs can be
divided into conduction and switching losses.
Conduction losses are related to the on resistance
of MOSFETs, and increase with the load current.
Switching losses occur on each on/off transition
when the MOSFETs experience both high current
and voltage. Since the bottom MOSFET switches
current from/to a paralleled diode (either its own
body diode or a Schottky diode), the voltage across
the MOSFET is no more than 1V during switching
transition. As a result, its switching losses are
negligible. The switching losses are difficult to
quantify due to all the variables affecting turn on/
off time. However, the following equation pro-
vides an approximation on the switching losses
associated with the top MOSFET driven by SP6132.
V
C
P
(max)
12
=
where
C
rss
= reverse transfer capacitance of the top
MOSFET
S
OUT
IN
rss
SH
F
I
(max)
(max)
Switching losses need to be taken into account for
high switching frequency, since they are directly
proportional to switching frequency. The conduc-
tion losses associated with top and bottom
MOSFETs are determined by:
D
I
R
P
OUT
ON
(
DS
CH
2
(max)
)
(max)
=
)
1
2
(max)
)
(
(max)
D
I
R
P
OUT
ON
DS
CL
=
where
P
CH(max)
= conduction losses of the high side
MOSFET
P
CL(max)
= conduction losses of the low side
MOSFET
R
DS(ON)
= drain to source on resistance.
The total power losses of the top MOSFET are the
sum of switching and conduction losses. For syn-
chronous buck converters of efficiency over 90%,
allow no more than 4% power losses for high or
low side MOSFETs. For input voltages of 3.3V
and 5V, conduction losses often dominate switch-
ing losses. Therefore, lowering the R
DS(ON)
of the
MOSFETs always improves efficiency even
though it gives rise to higher switching losses due
to increased
C
rss
.
Top and bottom MOSFETs experience unequal
conduction losses if their on time is unequal. For
applications running at large or small duty cycle, it
makes sense to use different top and bottom
MOSFETs. Alternatively, parallel multiple
MOSFETs to conduct large duty factor.
R
DS(ON)
varies greatly with the gate driver voltage.
The MOSFET vendors often specify R
DS(ON)
on
multiple gate to source voltages (V
GS
), as well as
provide typical curve of R
DS(ON)
versus V
GS
. For
5V input, use the R
DS(ON)
specified at 4.5V V
GS
. At
the time of this publication, vendors, such as
Fairchild, Siliconix and International Rectifier,
have started to specify R
DS(ON)
at V
GS
less than 3V.
This has provided necessary data for designs in
which these MOSFETs are driven with 3.3V and
made it possible to use SP6132 in 3.3V only
applications.
Thermal calculation must be conducted to ensure
the MOSFET can handle the maximum load cur-
rent. The junction temperature of the MOSFET,
determined as follows, must stay below the maxi-
mum rating.
JA
MOSFET
R
A
J
P
T
T
θ
(max)
(max)
(max)
+
=
where
T
A(max)
= maximum ambient temperature
P
MOSFET(max)
= maximum power dissipa-
tion of the MOSFET
R
Θ
JA
= junction to ambient thermal resistance.
R
Θ
JA
of the device depends greatly on the board
layout, as well as device package. Significant
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SP6132CU | Wide Input, 300KHz Synchronous PWM Controller |
| SP6132EB | Evaluation Board Manual |
| SP6132EU | Wide Input, 300KHz Synchronous PWM Controller |
| SP6132HV | High Voltage Synchronous Buck Controller |
| SP6133 | Evaluation Board Manual |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SP6132ACU | 制造商:Exar Corporation 功能描述:SMPS CONTROLLER |
| SP6132CU | 制造商:Exar Corporation 功能描述:DUAL SUPPLY LEAD FREE SYNCHRONOUS BUCK CONTROLLER |
| SP6132CU/TR | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Wide Input, 300KHz Synchronous PWM Controller |
| SP6132CU-L | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 Wide Input, 300kHz Synchronous RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| SP6132CU-L/TR | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 Wide Input, 300kHz Synchronous RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
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