參數(shù)資料
型號(hào)： SC4808BIMSTR
廠商： Semtech Corporation
英文描述： High Performance Dual Ended PWM Controller
中文描述： 高性能雙端PWM控制器
文件頁數(shù)： 18/31頁
文件大小： 483K
代理商： SC4808BIMSTR
18
2005 Semtech Corp.
www.semtech.com
SC4808A/B
POWER MANAGEMENT
Application Information (Cont.)
The instability can be corrected by modification of the peak
current information slope. One of the methods to alter the
peak current information is to add a positive going ramp to
the output of the current sensing circuitry.
The SC4808 achieves this by using an internal slope com-
pensation circuit. The oscillator ramp is internally buffered
and an internal 25kOhms resistor in conjunction with an
external resistor at the CS pin will program the level of slope
compensation.
Rosc
15k
R
10k
200p
RSlope Comp
2.2u,16V
C
82p
Cfilter
D
REF
Rsense
SC4808
4
5
3
2
1
6
7
FB
REF
CS
RC
SYNC
GND
N = 100
25k
Current Transformer
RSlope Comp value will determine the Mode of operation (Voltage or Current)
The Peak current information is sensed and the result is
realistically summed to the buffered oscillator ramp, as
shown above. The value of the external resistor R
will determine the percentage of the slope compensation.
As the value for R
is reduced, the current informa-
tion becomes more dominant and the mode of operation
becomes more current mode. At the same time the slope
of the current information is modified to provide the slope
compensation.
If the R
is increased, the internal ramp becomes the
dominant signal and more voltage mode of operation is
achieved. As it can be calculated from the second formula
below, a 100% voltage mode operation can be achieved by
choosing R
to be greater
than 6.25K ohms. Also if a
100% current mode of operation is required, R
is
reduced to zero and the contribution from the internal ramp
is completely eliminated.
(
)
(
)
CS
ernal
int
sense
Comp
V
_
slope
sense
+
Comp
R
+
_
slope
Ramp
V
R
R
R
R
Comp
_
Slope
%
+
×
=
or
(
)
(
2
)
×
×
Comp
_
slope
%
1
Comp
_
slope
%
2
R
R
ernal
int
external
Next page illustrates how the buffered oscillator ramp is
used to modify the sensed inductor current.
It should be noted that in order for the slope compensa-
tion to be effective, the current sensed signal slope should
be at least 50% less steeper than the oscillator positive
ramp slope. The slope will include the magnetizing current
of the transformer and the inductor output current in iso-
lated applications. In non-isolated applications, the slope
will only include the inductor output current.
相關(guān)PDF資料
PDF描述
SC4808BIMSTRT High Performance Dual Ended PWM Controller
SC4808B-1 High Performance Dual Ended PWM Controller
SC4808B-1MSTRT High Performance Dual Ended PWM Controller
SC4808B-2 High Performance Dual Ended PWM Controller
SC4808B-2MSTRT High Performance Dual Ended PWM Controller
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
SC4808BIMSTRT 制造商:Semtech Corporation 功能描述: 制造商:Semtech Corporation 功能描述:SC Series 20 mA 550 kHz SMT High Performance Dual Ended PWM Controller - MSOP-10
SC4808C 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:High Performance Dual Ended PWM Controller
SC4808CMSTRT 制造商:Semtech Corporation 功能描述:SC Series 20 mA 550 kHz SMT High Performance Dual Ended PWM Controller - MSOP-10
SC4809A 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:High Performance Current Mode PWM Controller
SC4809AIMSTR 制造商:Semtech Corporation 功能描述:IC, CURRENT MODE PWM CTRL, 12V, MSOP-10; Output Voltage:500mV; Output Current:1mA; Supply Voltage Min:0V; Supply Voltage Max:12V; Digital IC Case Style:MSOP; No. of Pins:10; Frequency:1MHz; Operating Temperature Min:-40C ;RoHS Compliant: No
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