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| 型号： | S-8460B00AFT-TB |
| 元件分类： | 稳压器 |
| 英文描述： | 0.1 A SWITCHING CONTROLLER, 345 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | TSSOP-16 |
| 文件页数： | 3/33页 |
| 文件大小： | 617K |
| 代理商： | S-8460B00AFT-TB |
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STEP-UP OR DOWN, SINGLE-COIL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.2_00
S-8460
Seiko Instruments Inc.
11
ON/OFF Pin
CR Oscillation
Circuit
All EXT Pin
Voltage
Output Voltage
“H”
Active
Set value
“L”
Non-active
VSS
Open
ON/OFF
VIN
VSS
Figure 12 ON/OFF Pin Structure
4. Overload Protection Circuit
The S-8460 contains a built-in overload protection circuit.
When the output voltage falls because of an overload despite the step-up operation or step-down, the S-8460
enters the step-up operation and holds the maximum duty step-up operation. If this maximum duty state lasts
longer than the overload detection time (tPRO), the overload protection circuit will hold the pins EXT1 to EXT3 at “L”
to protect the switching transistors and the inductor. When the overload protection circuit works, the output
voltage (VOUT) rises slowly since a soft start is carried out in the reference voltage circuit in the IC to raise the
reference voltage slowly from 0 V. If the load is still heavy at this time and the maximum duty step-up operation
lasts longer than tPRO, the overload protection circuit will work again. Repeat of this process leads to an operation
of intermittent mode. If the overload state is eliminated, the S-8460 goes back to the normal operation.
tPRO is determined by the external capacitor (CPRO). The approximate value of tPRO, which is from the beginning of
the maximum duty operation to the instant at which pin voltage of the EXT1 to EXT3 is held “L” to protect switching
transistors, is expressed by the following equation.
tPRO [ms]
= 0.0011 × CPRO [pF]
External Parts Selection
1. 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, the stability of the circuit is improved, and the
output current IOUT increases. As the L value is made even smaller, IOUT decreases since the current driveability of
the switching transistor 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 coil increases. IOUT also decreases.
An inductance of 22
H is recommended for the S-8460.
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
breakdown of the IC due to large current.
An inductor should therefore be selected so as not the peak current IPK to surpass its allowable current. IPK is
represented by the following equations in step-up operation and in step-down operation.
Comparing each
calculation result for step-up and step-down, larger value should be taken as the IPK. Adding some margin to the
obtained result, an inductor with the allowable current can be thus chosen.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| S-8460B00AFT-TBG | 功能描述:开关变换器、稳压器与控制器 2.5-6.0V Step-Up/Dwn RoHS:否 制造商:Texas Instruments 输出电压:1.2 V to 10 V 输出电流:300 mA 输出功率: 输入电压:3 V to 17 V 开关频率:1 MHz 工作温度范围: 安装风格:SMD/SMT 封装 / 箱体:WSON-8 封装:Reel |
| S846E2000M2 | 制造商:STEC Inc 功能描述:S800 SAS SSD 2.5" 15MM 2TB MLC COMMERCIAL (0C TO +60C) - Bulk |
| S846E200M1 | 制造商:STEC Inc 功能描述:S800 SAS SSD 1.8" 5MM 200GB MLC COMMERCIAL (0C TO +60C) - Bulk |
| S-8470 | 制造商:SII 制造商全称:Seiko Instruments Inc 功能描述:CMOS POWER MANAGEMENT IC |
| S-8470AFS | 制造商:SII 制造商全称:Seiko Instruments Inc 功能描述:CMOS POWER MANAGEMENT IC |
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