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參數(shù)資料
| 型號： | FAN7554 |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Versatile PWM Controller |
| 中文描述： | 1 A SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDIP8 |
| 封裝： | DIP-8 |
| 文件頁數(shù)： | 9/22頁 |
| 文件大?。?/td> | 1006K |
| 代理商： | FAN7554 |
FAN7554
9
Oscillator
As shown in figure14, the oscillator frequency is programmed by values selected for timing components Rt and C
t
. Capacitor
C
t
is charged to almost 2.8V through resistor Rt from the 5V reference and discharged to 1.2V by an internal current source.
The oscillator generates the clock signal while the timing capacitor C
t
is
discharged. The gate drive output becomes low during
the clock time. Rt and C
t
selection determine the oscillator frequency and maximum duty cycle. Charge and discharge times
can be calculated through the equations below.
Charging time : tc = 0.55
×
R
t
×
C
t
Discharging time : td = R
t
×
C
t
×
ln[(0.0063
×
R
t
- 2.8) / (0.0063
×
R
t
- 3.8)]
where the oscillator frequency : fosc = (tc + td)
-1
(±10%)
When R
t
> 5k
, fosc = 1 / (0.55
×
R
t
×
C
t
) = 1.8 / (R
t
×
C
t
)
Figure 13. Soft Start Circuit & Circuit Flow
2
FB
Vcc
5V
5uA
100uA
5V
1mA
R
Cs
Cfb
Output drive
FAN7554
1
2R
Ds
S/S
+
-
Clock
Figure 14. Oscillator Circuit
Figure 15. Sawtooth & Clock Waveform
Discharge
Ct
CT
Ct
4
Discharge
Gate Drive
8
Vref
Rt
FAN7554
/1.2V
2.8V
Vhigh(2.8V)
Vlow(1.2V)
Sawtooth waveform
Vhigh(2.8V)
Vlow(1.2V)
Sawtooth waveform
Internal clock
tc
td
tc
td
[ Rt > 5k
]
[ Rt < 5k
]
Internal clock
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| FAN7554_03 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:Versatile PWM Controller |
| FAN7554D | 功能描述:DC/DC 開關(guān)控制器 PWM Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| FAN7554D_Q | 功能描述:電流型 PWM 控制器 PWM Controller RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| FAN7554DTF | 功能描述:DC/DC 開關(guān)控制器 PWM Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| FAN7554DTF_Q | 功能描述:電流型 PWM 控制器 PWM Controller RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
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