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參數(shù)資料
| 型號： | S-8340A25AFT-T2 |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 0.1 A SWITCHING CONTROLLER, 690 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | TSSOP-8 |
| 文件頁數(shù)： | 14/53頁 |
| 文件大小： | 855K |
| 代理商： | S-8340A25AFT-T2 |
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STEP-UP, 600 kHz, PWM CONTROL OR PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.2.2_00
S-8340/8341 Series
Seiko Instruments Inc.
21
2. Inductor
The inductance value (L value) greatly affects the maximum output current (IOUT) and the efficiency (
η).
As the L value is reduced gradually, the peak current (IPK) increases and IOUT increases. As the L value is made
even smaller, IOUT decreases since the efficiency degrades and the current driveability is insufficient.
As the L value is increased, the dissipation in the switching transistor due to IPK decreases, and the efficiency
reaches the maximum at a certain L value. As the L value is made even larger, the efficiency degrades since the
dissipation due to the series resistance of the inductor increases. IOUT also decreases.
In the S-8340/8341 Series, as the L value is increased, the output voltage may be unstable depending on the
conditions of the input voltage, output voltage, and load current. Select the L value after performing a thorough
valuation under actual use conditions. The guidelines for the L range are from 2.2 to 22
H for the A and B types,
and 4.7 to 47
H for the C and D types.
The recommended L value is 5 to 10
H for the A and B types, and 10 to 22 H for the C and D types.
When choosing an inductor, attention to its allowable current should be paid since the current exceeding the
allowable value will cause magnetic saturation in the inductor, leading to a marked decline in efficiency and a
breakdown of the IC due to large current.
An inductor should therefore be selected so that IPK does not surpass its allowable current. IPK is represented by
the following equations in non-continuous operation mode.
IPK
=
2I
V
fosc
OUT
F
IN
()
L
××
+
×
Where fOSC is the oscillation frequency, L is the inductance value of the inductor, and VF is the forward voltage of
the diode. VF should be appropriately 0.4 V.
For example, if a power supply with the input voltage (VIN)
= 3 V, output voltage (VOUT) = 5 V, and load current (IOUT)
= 30 mA is used, fOSC = 600 kHz when the S-8340A50AFT is used. When 10 H is selected for the L value, IPK =
155 mA from the above formula. Therefore, in this case, an inductor with a permissible current of 155 mA or higher
for the L value of 10
H should be selected.
3. Diode
Use an external diode that meets the following requirements :
Low forward voltage (Schottky barrier diode is recommended.)
High switching speed (50 ns max.)
The reverse-direction withstand voltage is VOUT
+ VF or higher.
The current rating is IPK or larger.
4. Capacitors (CIN, CL)
A capacitor inserted on the input side (CIN) improves the efficiency by reducing the power impedance and stabilizing
the input current. Select a CIN value according to the impedance of the power supply used. Approximately 47 to
100
F is recommended for a capacitance depending on the impedance of the power source and load current
value.
For the output side capacitor (CL), select a large capacitance with low ESR (Equivalent Series Resistance) for
smoothing the ripple voltage. When the input voltage is extremely high or the load current is extremely large, the
output voltage may become unstable. In this case the unstable area will become narrow by selecting a large
capacitance for an output capacitor. A tantalum electrolyte capacitor is recommended since the unstable area
widens when a capacitor with a large ESR, such as an aluminum electrolyte capacitor, or a capacitor with a small
ESR, such as a ceramic capacitor, is chosen.
It is recommended that a capacitor of which the capacitance is 47 to 200
F and ESR is 40 to 270 m be selected.
Fully evaluate input and output capacitors under actual operating conditions, then select them.
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相關(guān)代理商/技術(shù)參數(shù) |
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| S-8340A25AFT-T2-G | 功能描述:DC/DC 開關(guān)控制器 2.5V Step-Up 2.0% 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 |
| S-8340A30AFT-T2 | 功能描述:DC/DC 開關(guān)控制器 3.0V Step-Up 2.0% 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 |
| S-8340A30AFT-T2-G | 功能描述:DC/DC 開關(guān)控制器 3.0V Step-Up 2.0% 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 |
| S-8340A33AFT-T2 | 功能描述:DC/DC 開關(guān)控制器 3.3V Step-Up 2.0% 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 |
| S-8340A33AFT-T2-G | 功能描述:DC/DC 開關(guān)控制器 3.3V Step-Up 2.0% 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 |
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