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參數(shù)資料
| 型號： | SP6127 |
| 英文描述： | High-Voltage, Step-Down Controller in TSOT6 |
| 中文描述： | 高電壓，降壓型控制器在TSOT6 |
| 文件頁數(shù)： | 7/12頁 |
| 文件大?。?/td> | 564K |
| 代理商： | SP6127 |
______________________________________________________
GENERAL OVERVIEW
June 26, 2007 SP6127 TSOT-6 PFET Buck Controller
2007 Sipex Corporation
Page 7
MOSFET Gate Drive
The P-channel drive is derived through an
internal regulator that generates V
IN
-5V. This pin
(VDR) must be connected to V
IN
with a 0.1
μ
F
decoupling capacitor. The gate drive circuit
swings between V
IN
and V
IN
-5 and employs
powerful drivers for efficient switching of the P-
channel MOSFET.
Power MOSFET Selection
Select the Power MOSFET for Voltage rating
BV
DSS
, On resistance R
DS
(
ON
), and thermal
resistance R
THJA
. BV
DSS
should be about twice
as high as V
IN
in order to guard against switching
transients. The recommended MOSFET voltage
rating for V
IN
of 5V, 12V and 24V is 12V, 30V and
40V respectively. R
DS
(
ON
)
must be selected such
that when operating at peak current and junction
temperature, the Overcurrent threshold of the
SP6127 is not exceeded. Allowing 50% for
temperature coefficient of R
DS
(
ON
) and 15% for
inductor current ripple, the following expression
can be used:
≤
ON
RDS
5
Within this constraint, selecting MOSFETs with
lower R
DS
(
ON
) will reduce conduction losses at
the expense of increased switching losses. As a
rule of thumb, select the highest R
DS
(
ON
)
MOSFET that meets the above criteria. Switching
losses can be assumed to roughly equal to the
conduction losses. A simplified expression for
conduction losses is given by:
×
×
Iout
V
15
.
3
)
(
×
×
=
Vin
Vout
ON
(
RDS
Iout
Pcond
)
2
The MOSFET’s junction temperature can be
estimated from:
(
Rthja
Pc
T
×
×
=
2
Schottky Rectifier selection
Select the Schottky Diode for Voltage rating V
R
,
Forward voltage V
f
, and thermal resistance
R
THJA
. The Voltage rating should be selected
using the same guidelines outlined for MOSFET
)
Tambient
+
voltage selection. For a low duty cycle application
such as the circuit shown on first page, the
Schottky diode is conducting most of the time and
its conduction losses are the largest component
of losses in the converter. Conduction losses can
be estimated from:
1
×
×
=
Vin
Vout
Iout
Vf
Pc
where:
V
F
is diode forward voltage at
I
OUT
The Schottky diode’s AC losses due to its
switching capacitance are negligible.
Inductor Selection
Select the Inductor for inductance L and
saturation current
I
SAT
. Select an inductor with
I
SAT
higher than the programmed overcurrent.
Calculate inductance from:
×
=
Vin
(
)
×
×
Irip
f
Vout
Vout
Vin
L
1
1
where:
V
IN
is converter input voltage
V
OUT
is converter output voltage
f
is switching frequency
I
RIP
is inductor peak-to-peak current ripple
(nominally set to 30% of
I
OUT
)
Keep in mind that a higher
I
RIP
results in a
smaller inductor which has the advantages of
small size, low DC equivalent resistance DCR,
high saturation current
I
SAT
and allows the use of
a lower output capacitance to meet a given step
load transient. A higher
I
RIP
, however, increases
the output voltage ripple and increases the
current at which converter enters Discontinuous
Conduction Mode. The output current at which
converter enters DCM is of
I
RIP
. Note that a
negative current step load that drives the
converter into DCM will result in a large output
voltage transient. Therefore the lowest current for
a step load should be larger than of
I
RIP
.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SP6127_07 | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Evaluation Board Manual |
| SP6127EB | 功能描述:電源管理IC開發(fā)工具 Eval Board for SP6127 Series RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| SP6127EK1 | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Evaluation Board Manual |
| SP6127EK1L | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:High-Voltage, Step-Down Controller in TSOT6 |
| SP6127EK1-L | 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
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