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| 型号： | S-8520B31MC-ARQ-T2 |
| 元件分类： | 稳压器 |
| 英文描述： | 0.05 A SWITCHING CONTROLLER, 216 kHz SWITCHING FREQ-MAX, PDSO5 |
| 封装： | SOT-23, 5 PIN |
| 文件页数： | 9/43页 |
| 文件大小： | 488K |
| 代理商： | S-8520B31MC-ARQ-T2 |
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STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00
S-8520 / 8521 Series
Seiko Instruments Inc.
17
2. Inductor
The inductance value (L) greatly affects the maximum output current (IOUT) and the efficiency (
η).
The peak current (IPK) increases by decreasing L and the stability of the circuit improves and IOUT
increases. If L is made even smaller, the efficiency falls causing a decline in the current drive capacity
for the switching transistor, and IOUT decreases.
The loss of IPK by the switching transistor decreases by increasing L and the efficiency becomes
maximum at a certain L value. Increasing L further decreases the efficiency due to the loss of coil DC
resistance. IOUT also decreases.
When the inductance is large in an S-8520 / 8521 series product, the output voltage may grow unstable in
some cases, depending on the conditions of the input voltage, output voltage, and the load current.
Perform sufficient evaluation under the actual condition and decide an optimum inductance.
The recommended inductances are 47
H for A, B, C, D types and 22 H for E, F types.
When choosing an inductor, attention to its allowable current should be paid since the current over the
allowable value will cause magnetic saturation in the inductor, leading to a marked decline in efficiency.
An inductor should therefore be selected so as not IPK to surpass its allowable current. The peak current
(IPK) is represented by the following equation in non-continuous operation mode:
)
V
(
L
f
2
)
V
(
)
V
(
I
F
IN
osc
OUT
IN
F
OUT
PK
+
×
×
+
=
Where fosc is the oscillation frequency, and VF the forward voltage of the diode.
3. Diode
The diode to be externally coupled to the IC should be a type that meets the following conditions:
Its forward voltage is low (Schottky barrier diode recommended).
Its switching speed is high (50 ns max.).
Its reverse direction voltage is higher than VIN.
Its current rating is higher than IPK.
4. Capacitors (CIN, COUT)
The capacitor inserted on the input side (CIN) serves to lower the power impedance and to average the
input current for better efficiency. Select the CIN value according to the impedance of the power
supplied. As a rough rule of thumb, you should use a value of 47 to 100
F, although the actual value
will depend on the impedance of the power in use and the load current value.
For the output side capacitor (COUT), select one of large capacitance with low ESR (Equivalent Series
Resistance) for smoothing the ripple voltage. However, notice that a capacitor with extremely low ESR
(say, below 0.3
), such as a ceramic capacitor, could make the output voltage unstable, depending on
the input voltage and load current conditions. Instead, a tantalum electrolytic capacitor is recommended.
A capacitance value from 47 to 100
F can serve as a rough yardstick for this selection.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| S-8520B31MC-ARQT2G | 功能描述:DC/DC 开关控制器 3.1V Step-Down PWM RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| S-8520B32MC-ARR-T2 | 功能描述:DC/DC 开关控制器 3.2V Step-Down PWM RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| S-8520B32MC-ARRT2G | 功能描述:DC/DC 开关控制器 3.2V Step-Down PWM RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| S-8520B33MC-ARS-T2 | 功能描述:DC/DC 开关控制器 3.3V Step-Down PWM RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| S-8520B33MC-ARST2G | 功能描述:DC/DC 开关控制器 3.3V Step-Down PWM RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
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