參數(shù)資料
型號(hào)： AS3844D14T
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(yè)數(shù)： 13/20頁(yè)
文件大小： 155K
代理商： AS3844D14T
13
ASTEC Semiconductor
(2)
(3)
(4)
where f
osc
is the oscillator frequency, D is the
maximum duty ratio, V
H
is the oscillators upper
trip point, V
L
is the lower trip point, V
R
is the Ref-
erence 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 AS3842 oscillator,
once the final values are determined, they will
yield repeatable results, thus eliminating the
need for additional trimming of the timing compo-
nents during manufacturing.
1.3.2 Oscillator enhancements
The AS3842 oscillator is trimmed to provide
guaranteed duty ratio clamping. This means that
the discharge current (I
D
) is trimmed to a value
that compensates for all of the tolerances within
the device (such as the tolerances of V
REG
, prop-
agation delays, the oscillator trip points, etc.)
which have an effect on the frequency and max-
imum duty ratio. For example, if the combined
tolerances of a particular device are 0.5% above
nominal, then I
D
is trimmed to 0.5% above nomi-
nal. This method of trimming virtually eliminates
the need to trim external oscillator components
during power supply manufacturing. Standard
3842 devices specify or trim only for a specific
value of discharge current. This makes precise
AS384x
Current Mode Controller
Table 1. R
T
vs Maximum Duty Ratio
R
T
()
Dmax
470
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%
R
V
I
T
REG
D
=
￥
(K
L
)
D
1D
D
D
(K
H
)
D
1D
D
(K
L
)
D
1
D
(K
H
)
D
1
K
V
H
REG
=
≈
V
V
H
H
0.432
(
K
V
L
REG
V
=
≈
V
L
REG
0.736
D
D
=
1D
D
1D
D
582 ￥
(0.432)
(0.736)
D
D
1
1
(0.432)
(0.736)
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參數(shù)描述
AS3844D813 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Current Mode Controller
AS3844D8T 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Current Mode Controller
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AS3844NT 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Current Mode Controller
AS3845 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Current Mode Controller
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