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參數(shù)資料
| 型號： | SI9117 |
| 廠商： | Vishay Intertechnology,Inc. |
| 英文描述： | High-Frequency Converter for Telecom Applications |
| 中文描述： | 高頻轉換器的電信應用 |
| 文件頁數(shù)： | 10/15頁 |
| 文件大小： | 132K |
| 代理商： | SI9117 |
Si9117
Vishay Siliconix
www.vishay.com
10
Document Number: 70027
S-40750—Rev. E, 19-Apr-04
Feedback
Comparator
UV-low
V
REF
4.6 V
20 A
C
SS
Error Amp
FIGURE 4.
Soft-Start
Oscillator
The oscillator circuit uses external timing components R
T
and
C
T
. An internal divide-by-two prevents pulses with greater than
50% duty cycle, so that core saturation can be avoided. When
the R
T
terminal is connected to V
CC
, comparator C
2
disconnects the oscillator output from the SYNC terminal using
SW
1
, and allows an external oscillator circuit to take control of
the current mode comparator circuit.
The current programmed by R
T
defines the charging current of
C
T
and the on and off times with the following design
equations:
T
ON
1.025 x R
T
x C
T
8
T
OFF
5 x R
ql
x C
T
F
OSC
1
2x
1
T
ON
T
OFF
(1)
(2)
(3)
where R
ql
= 25
Actual values taken from a prototype board have been
plotted (Figure 6), and are a close match (except for 47 pF,
where stray parasitics have a more significant effect).
In certain circumstances, such as current limiting, it may be
desirable to change the frequency of the converter for a period
of time to overcome current tails (see Figure 14 for further
explanation). With the Si9117, this is easily done by adding or
subtracting some current into the R
T
terminal:
The charging current in C
T
is set by 8
R
T.
The voltage at the R
T
terminal is 4 V, as supplied by an inter-
nal emitter follower from the reference.
The frequency can be changed easily by supplying some of
the current into R
T
from the V
CC
rail, thus “starving” the
internal current source, and slowing the frequency down.
(See Figure 7.)
I
1
C
1
V
REF
C
2
I
2
Q
2
B
1
B
2
B
3
SW
1
Q
1
C
T
R
T
U
1
D
Q
Q
CLK
SYNC
FIGURE 5.
Oscillator
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| SI9117DY | 功能描述:直流/直流開關轉換器 1MHz HV Sw Mode Reg RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
| SI9117DY-E3 | 功能描述:開關變換器、穩(wěn)壓器與控制器 Hi Freq Converter For Telecom App RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| SI9117DY-T1 | 功能描述:直流/直流開關轉換器 Hi Freq Converter For Telecom App RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
| SI9117DY-T1-E3 | 功能描述:開關變換器、穩(wěn)壓器與控制器 Hi Freq Converter For Telecom App RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| SI9118 | 制造商:VISHAY 制造商全稱:Vishay Siliconix 功能描述:Programmable Duty Cycle Controller |
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