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| 型号： | S-8340A25AFT-T2 |
| 元件分类： | 稳压器 |
| 英文描述： | 0.1 A SWITCHING CONTROLLER, 690 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封装： | TSSOP-8 |
| 文件页数： | 8/53页 |
| 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
S-8340/8341 Series
Rev.2.2_00
Seiko Instruments Inc.
16
Operation
1. Switching Control Method
1. 1 PWM Control (S-8340 Series)
The S-8340 Series is a DC-DC converter using a pulse width modulation method (PWM).
In conventional PFM DC-DC converters, pulses are skipped when the output load current is low, causing a
fluctuation in the ripple frequency of the output voltage, resulting in an increase in the ripple voltage.
The switching frequency does not change, although the pulse width changes from 0 to 82% corresponding to each
load current in the S-8340 Series. The ripple voltage generated from switching can thus be eliminated easily
through a filter. When the pulse width is 0% (when no load is applied or the input voltage is high), pulses are
skipped and the current consumption is low.
1. 2 PWM/PFM Switching Control (S-8341 Series)
The S-8341 Series is a DC-DC converter that automatically switches between a pulse width modulation method
(PWM) and a pulse frequency modulation method (PFM) depending on the load current.
The S-8341 Series operates under PWM control with the pulse duty changing from 27 to 82% (A and B types) and
from 21 to 82% (C and D types) in a high output load current area.
The S-8341 Series operates under PFM control with the pulse duty fixed at 27% (A and B types) and at 21% (C and
D types) in a low load current area, and pulses are skipped according to the load current. The oscillation circuit
thus oscillates intermittently so that the resultant lower self current consumption prevents a reduction in the
efficiency at a low load current. The switching point from PWM control to PFM control depends on the external
devices (coil, diode, etc.), and input and output voltage values. The S-8341 Series is an especially highly efficient
DC-DC converter at an output load current around 1 mA.
2. Soft-Start Function
The S-8340/8341 Series has a built-in soft-start circuit.
This circuit enables the output voltage (VOUT) to rise gradually over the specified soft-start time (tSS) to suppress the
overshooting of the output voltage and the rush current from the power supply when the power is switched on or the
ON/OFF pin is changed to “H”.
Generally, a rush current flows to an output capacitor through an inductor and a diode in the step-up circuit
immediately after the power is turned on as shown in Figure 9. Note that the soft-start function of this IC, however,
does not limit this current.
t (2 m s /d iv )
O u tput v o ltage
(1 V /d iv )
R u sh cu rre n t
(0 .5 A /d iv )
3 V
0 V
1.5 A
0 A
S -8340A 33A F T (V IN
= 0 → 1.9 V , R L = 300 k )
Figure 9 Waveforms of Output Voltage and Rush Current at Soft-Start
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相关代理商/技术参数 |
参数描述 |
|---|---|
| S-8340A25AFT-T2-G | 功能描述:DC/DC 开关控制器 2.5V Step-Up 2.0% 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-8340A30AFT-T2 | 功能描述:DC/DC 开关控制器 3.0V Step-Up 2.0% 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-8340A30AFT-T2-G | 功能描述:DC/DC 开关控制器 3.0V Step-Up 2.0% 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-8340A33AFT-T2 | 功能描述:DC/DC 开关控制器 3.3V Step-Up 2.0% 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-8340A33AFT-T2-G | 功能描述:DC/DC 开关控制器 3.3V Step-Up 2.0% 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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