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參數(shù)資料
| 型號： | EL7571C |
| 英文描述： | Programmable PWM Controller |
| 中文描述： | 可編程PWM控制器 |
| 文件頁數(shù)： | 23/23頁 |
| 文件大小： | 480K |
| 代理商： | EL7571C |
9
EL7571C
Programmable PWM Controller
E
L
75
71
C
tion. The following table lists some of the differences
between the various configurations:
Circuit schematics and Bills of Material (BOMs) for the
various topologies are provided at the end of this data
sheet. If your application requirements differ from the
included samples, the following design guide lines
should be used to select the key component values.
Refer to the front page connection diagram for compo-
nent locations.
Output Inductor, L1
Two key converter requirements are used to determine
inductor value:
IMIN- minimum output current; the current level at
which the converter enters the discontinuous mode of
operation (refer to Elantec application note #18 for a
detailed discussion of discontinuous mode)
IMAX- maximum output current
Although many factors influence the choice of the
inductor value, including efficiency, transient response
and ripple current, one practical way of sizing the induc-
tor is to select a value which maintains continuous mode
operation, i.e. inductor current positive for all condi-
tions. This is desirable to optimize load regulation and
light load transient response. When the minimum induc-
tor ripple current just reaches zero and with the mean
ripple current set to IMIN, peak inductor ripple current is
twice IMAX, independent of duty cycle. The minimum
inductor value is given by:
where:
IPEAK = peak ripple current
TON = top switch on time
VIN = input voltage
FSW = switching frequency
VOUT = output voltage
IMIN = minimum load
Since inductance value tends to decrease with current,
ripple current will generally be greater than 21MIN 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 rec-
ommend the Micrometals Powered Iron Cores data
sheet and applications note as a good reference and start-
ing point.
Current Sense Resistor, R1
Inductor current is monitored indirectly via a low value
resistor R1. The voltage developed across the current
sense resistor is used to set the maximum operating cur-
rent, 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.
Converter Topologies
Topology
Diagram
Efficiency
Cost
Complexity
Input Noise
Transient
Response
5V only Non-synchronous
figure 1
92%
low
high
good
5V only Synchronous
figure 2
95%
higher
high
good
5V &12V Non-synchronous
figure 3
92%
lowest
high
good
5V & 12V Synchronous
figure 4
95%
high
good
12V only Synchronous
Connection
Diagram
92%
highest
high
best
L1MIN
V
( IN VOUT) TON
×
–
1PEAK
-----------------------------------------------------
V
( IN VOUT) VOUT
×
–
VIN FSW 2 IMIN
×
---------------------------------------------------------
==
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| 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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