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參數(shù)資料
| 型號： | EL7571 |
| 廠商： | Intersil Corporation |
| 英文描述： | Programmable PWM Controller |
| 中文描述： | 可編程PWM控制器 |
| 文件頁數(shù)： | 9/19頁 |
| 文件大小： | 310K |
| 代理商： | EL7571 |
9
where:
I
PEAK
= peak ripple current
T
ON
= top switch on time
V
IN
= input voltage
F
SW
= switching frequency
V
OUT
= output voltage
I
MIN
= minimum load
Since inductance value tends to decrease with current,
ripple current will generally be greater than 21
MIN
at higher
output current.
Once the minimum output inductance is determined, an off
the shelf inductor with current rating greater than the
maximum DC output required can be selected.
Pulse
Engineering
and
Coil Craft
are two manufactures of high
current inductors. For converter designers who want to
design their own high current inductors, for experimental
purposes or to further reduce costs, we recommend the
Micrometals Powered Iron Cores
data sheet and
applications note as a good reference and starting point.
Current Sense Resistor, R
1
Inductor current is monitored indirectly via a low value
resistor R
1
. The voltage developed across the current sense
resistor is used to set the maximum operating current, the
current reversal threshold and the system load regulation. To
ensure reliable system operation it is important to sense the
actual voltage drop across the resistor. Accordingly a four
wire Kelvin connection should be made to the controller
current sense inputs. There are two criteria for selecting the
resistor value and type. Firstly, the minimum value is limited
by the maximum output current. The EL7571 current limit
capacitor has a typical threshold of 154mV, 125mV
minimum. When the voltage across the sense resistor
exceeds this threshold, the conduction cycle of the top
switch terminates immediately, providing pulse by pulse
current limiting. A resistor value must be selected which
guarantees operation under maximum load. That is:
where:
V
OCMIN
= minimum over current voltage threshold
I
MAX
= maximum output current
Secondly, since the load current passes directly through the
sense resistor, its power rating must be sufficient to handle
the power dissipated during maximum load (current limit)
conditions. Thus:
where:
P
D
= power dissipated in current sense resistor
P
D
must be less than the power rating of the current sense
resistor. High current applications may require parallel sense
resistors to dissipate sufficient power. Current Sense
Resistor Table below lists some popular current sense
resistors: the WLS-2512 series of Power Metal Strip
Resistors from Dale Electronics, OARS series Iron Alloy
resistor from IRC, and Copper Magnanin (CuNi) wire resistor
from Mills Resistors. Mother board copper trace is not
recommended because of its high temperature coefficient
and low power dissipation. The trade-off between the
different types of resistors are cost, space, packaging and
performance. Although Power Metal Strip Resistors are
relatively expensive, they are available in surface mount
packaging with tighter tolerances. Consequently, less board
space is used to achieve a more accurate current sense.
Alternatively, Magnanin copper wire has looser tolerance
and higher parasitic inductance. This results in a less current
sense but at a much lower cost. Metal track on the PCB can
also be used as current sense resistor. The trade-offs are
±30% tolerance and ±4000 ppm temperature coefficient.
Ultimately, the selection of the type of current sense element
must be made on an application by application basis.
R
1
V
MAX
----------------------
=
P
D
1
OUTMAX
2
R
1
×
=
Bill of Materials
MANUFACTURER
PART NO.
TOLERANCE
TEMPERATURE
COEFFICIENT
POWER RATING
PHONE NO.
FAX NO.
Dale
WSL 2512
±1%
±75ppm
1W
402-563-6506
402-563-6418
IRC
OARS Series
±5%
±20ppm
1W - 5W
800-472-6467
800-472-3282
Mills Resistor
MRS1367-TBA
±10%
±20ppm
1.2W
916-422-5461
906-422-1409
PCB Trace Resistor
±30%
±4000ppm
50A/in (1oz Cu)
EL7571
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| EL7571C | 制造商:ELANTEC 制造商全稱:ELANTEC 功能描述:Programmable PWM Controller |
| EL7571CM | 功能描述:IC CTRLR PWM PROGRAMMABLE 20SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 產(chǎn)品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,000 系列:- 應用:電源，ICERA E400，E450 輸入電壓:4.1 V ~ 5.5 V 輸出數(shù):10 輸出電壓:可編程 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:42-WFBGA，WLCSP 供應商設備封裝:42-WLP 包裝:帶卷 (TR) |
| EL7571CM-T13 | 功能描述:IC CTRLR PWM PROGRAMMABLE 20SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 產(chǎn)品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,000 系列:- 應用:電源，ICERA E400，E450 輸入電壓:4.1 V ~ 5.5 V 輸出數(shù):10 輸出電壓:可編程 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:42-WFBGA，WLCSP 供應商設備封裝:42-WLP 包裝:帶卷 (TR) |
| EL7571CMZ | 功能描述:IC CTRLR PWM PROGRAMMABLE 20SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 產(chǎn)品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,000 系列:- 應用:電源，ICERA E400，E450 輸入電壓:4.1 V ~ 5.5 V 輸出數(shù):10 輸出電壓:可編程 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:42-WFBGA，WLCSP 供應商設備封裝:42-WLP 包裝:帶卷 (TR) |
| EL7571CMZ-T13 | 功能描述:IC CTRLR PWM PROGRAMMABLE 20SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 產(chǎn)品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,000 系列:- 應用:電源，ICERA E400，E450 輸入電壓:4.1 V ~ 5.5 V 輸出數(shù):10 輸出電壓:可編程 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:42-WFBGA，WLCSP 供應商設備封裝:42-WLP 包裝:帶卷 (TR) |
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