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參數資料
| 型號： | SP6122ACU-15 |
| 英文描述： | Low Voltage, Micro 8, PFET, Buck Controller Ideal for 1A to 5A, Small Footprint, DC-DC Power Converters |
| 中文描述： | 低電壓，微8，PFET的，降壓控制器適合第1A至5A，占地面積小，DC - DC電源轉換器 |
| 文件頁數： | 16/19頁 |
| 文件大?。?/td> | 174K |
| 代理商： | SP6122ACU-15 |
16
Date: 10/02/04
SP6122 Low Voltage, Micro 8, PFET, Buck Controller Copyright 2004 Sipex Corporation
R
DS(ON)
OVER CURRENT PROTECTION
Fault conditions are detected via an over
voltage condition across the PMOS switch
during conduction. This is commonly known
as R
DS(ON)
sensing. R
DS(ON)
sensing is inac-
curate but efficient and is used where an
indicator of over current behavior is required
for protection. Two advanced features are
incorporated in the SP6122 R
DS(ON)
sensing
scheme. The sensing environment is very
noisy. Typical schemes require some exter-
nal filtering in order to avoid spurious faults
due to noise or load transients, often com-
promising the protection and performance
at low duty ratios. The SP6122 incorporates
a 10
μ
s internal sample and hold filter after
the main sense comparator. In this fashion,
small pulse widths can be detected while
maintaining adequate filtering against false
glitches. In addition, temperature compen-
sation is added such that the over current
detection threshold at any temperature can
be calculated with reasonable accuracy at
room temperature. For our evaluation board
example:
I
TRIP
= (150mV + I
SET
R
SET
)/R
DS(ON)
=
(150mV + 20
μ
A*1k
)/25m
= 6.8A
This is the about the same trip threshold at
room, hot or cold because a temperature
coefficient has been added to both the 150mV
and the 20
μ
A set currents. This temperature
coefficient tracks the 25m
R
DS(ON)
of the
external FET. Due to the small size of these
power supplies, thermal coupling exists be-
tween the PFET and the SP6122, making
this thermal compensation reasonable, but
not perfect. Notice there is about a 50% pad
between the maximum usable current (5A)
and the over current trip threshold (7A) in
order to accommodate PFET and overall
system variation.
Layout Guidelines
PCB layout plays a critical role in proper
function of the converters and EMI control.
In switch mode power supplies, loops carry-
ing high di/dt give rise to EMI and ground
bounce. The goal of layout optimization is to
identify these loops and minimize them. It is
also crucial on how to connect the controller
ground such that its operation is not affected
by noise. The following guidelines should be
followed to ensure proper operation.
1. A ground plane is recommended for
minimizing noises, copper losses and
maximizing heat dissipation.
2. Connect the ground of the feedback
divider to the GND pin of the IC. Then
connect this pin as close as possible to
the ground of the output capacitor.
3. The Vcc bypass capacitor should be right
next to the Vcc and GND pins.
4. The traces connecting to the feedback
resistors and current sense components
should be short and far away from the
switch node and switching components.
5. Minimize the trace length/maximize the
trace width between the PDRV pin and
the gate of the PMOS.
6. Minimize the loop composed of input
capacitors, PMOS and Schottky diode,
as this loop carries high di/dt current.
Also increase the trace width to reduce
copper losses.
7. Maximize the trace width of the loop
connecting the inductor, output capaci-
tors, and Schottky diode.
8. For an layout example of an SP6122
power supply (3.3Vin and 1.9Vout at 4A)
see the SP6122 Evaluation Board
Manual.
Features and Protection:
continued
相關PDF資料 |
PDF描述 |
|---|---|
| SP6122CU | Evaluation Board Manual |
| SP6122EB | Evaluation Board Manual |
| SP6122UEB | Evaluation Board Manual |
| SP6122ACU-1.5 | Low Voltage, Micro 8, PFET, Buck Controller Ideal for 1A to 5A, Small Footprint, DC-DC Power Converters |
| SP6122 | Low Voltage, Micro 8, PFET, Buck Controller Ideal for 1A to 5A, Small Footprint, DC-DC Power Converters |
相關代理商/技術參數 |
參數描述 |
|---|---|
| SP6122ACU-15/TR | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Low Voltage, Micro 8, PFET, Buck Controller Ideal for 1A to 5A, Small Footprint, DC-DC Power Converters |
| SP6122ACU-L | 功能描述:DC/DC 開關控制器 Low Voltage, Micro 8 PFET Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| SP6122ACU-L/TR | 功能描述:DC/DC 開關控制器 Low Voltage, Micro 8 PFET Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| SP6122ACU-L-1-5 | 制造商:Exar Corporation 功能描述:BUCK CONTROLLER LOW VOLT PFET 6122 |
| SP6122CU | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Evaluation Board Manual |
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