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參數(shù)資料
| 型號： | AS2845D-8 |
| 廠商： | Electronic Theatre Controls, Inc. |
| 英文描述： | Current Mode Controller |
| 中文描述： | 電流模式控制器 |
| 文件頁數(shù)： | 13/20頁 |
| 文件大?。?/td> | 94K |
| 代理商： | AS2845D-8 |
ASTEC Semiconductor
Current Mode Controller
AS2842/3/4/5
49
Table 1. R
T
vs Maximum Duty
Ratio
R
T
(
)
470
Dmax
22%
560
37%
683
50%
750
54%
820
58%
910
63%
1,000
66%
1,200
72%
1,500
77%
1,800
81%
2,200
85%
2,700
88%
3,300
90%
3,900
91%
4,700
93%
5,600
94%
6,800
95%
8,200
96%
10,000
97%
18,000
98%
that compensates for all of the tolerances within
the device (such as the tolerances of V
REG
,
propagation delays, the oscillator trip points,
etc.) which have an effect on the frequency and
maximum duty ratio. For example, if the com-
bined tolerances
of a particular device are 0.5%
above nominal, then I
D
is trimmed to 0.5% above
nominal. This method of trimming virtually
eliminates the need to trim external oscillator
components during power supply manufactur-
K
V
L
REG
V
=
≈
( )
3
V
L
REG
0.736
K
V
H
REG
=
≈
( )
4
V
V
H
H
0.4
32
where f
osc
is the oscillator frequency, D is the
maximum duty ratio, V
H
is the oscillator’s upper
trip point, V
L
is the lower trip point, V
R
is the
Reference voltage, I
D
is the discharge current.
Table 1 lists some common values of R
T
and the
corresponding maximum duty ratio. To select the
timing components; first, use Table 1 or equation
(2) to determine the value of R
T
that will yield the
desired maximum duty ratio. Then, use equation
(1) to calculate the value of C
T.
For example, for
a switching frequency of 250 kHz and a maxi-
mum duty ratio of 50%, the value of R
T
, from
Table 1, is 683
. Applying this value to equation
(1) and solving for C
T
gives a value of 4700 pF. In
practice, some fine tuning of the initial values
may be necessary during design. However, due
to the advanced design of the AS2842 oscillator,
once the final values are determined, they will
yield repeatable results, thus eliminating the need
for additional trimming of the timing components
during manufacturing.
1.3.2 Oscillator enhancements
The AS2842 oscillator is trimmed to provide
guaranteed duty ratio clamping. This means that
the discharge current (I
D
) is trimmed to a value
R
V
I
K
)
K
K
K
T
REG
D
L
H
L
H
D
D
D
D
D
D
D
D
D
D
D
D
=
(
)
(
(
)
)
(
( )
2
=
(
(0 736
)
(
)
)
1
1
1
1
1
1
1
1
582
0 736
.
0 432
.
(0 432
–
–
)
相關(guān)PDF資料 |
PDF描述 |
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| AS2845N | Current Mode Controller |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AS2845N | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Current Mode Controller |
| AS284R5FLF | 制造商:TT Electronics / IRC 功能描述:AS284R5FLF |
| AS284R5HLF | 制造商:TT Electronics / IRC 功能描述:AS284R5HLF |
| AS284R5JLF | 制造商:TT Electronics / IRC 功能描述:AS284R5JLF |
| AS2850 | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:5A Low Dropout Voltage Regulator Adjustable & Fixed Output, Fast Response |
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