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| 型号： | S-8338AAHB-T8T1G |
| 元件分类： | 稳压器 |
| 英文描述： | 0.16 A SWITCHING CONTROLLER, 1246.3 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封装： | LEAD FREE, TSSOP-8 |
| 文件页数： | 10/51页 |
| 文件大小： | 446K |
| 代理商： | S-8338AAHB-T8T1G |
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STEP-UP, 1.2 MHz HIGH-FREQUENCY, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8337/8338 Series
Rev.4.0_00
18
Seiko Instruments Inc.
4. External transistor
A bipolar (NPN) or enhancement (N-channel) MOS FET transistor can be used as the external
capacitor.
4. 1 Bipolar (NPN) type
The driving capability when the output current is increased by using a bipolar transistor is
determined by hFE and Rb of the bipolar transistor. Figure 11 shows a peripheral circuit.
Nch
Pch
Rb
VIN
IPK
EXT
Cb
2200 pF
1 k
Ω
Figure 11 External Transistor Periphery
1 k
Ω is recommended for R
b. Actually, calculate the necessary base current (Ib) from hFE of the
bipolar transistor as follows and select an Rb value lower than this.
Ib =
hFE
IPK
Rb =
Ib
VIN – 0.7
–
IEXTH
0.4
A small Rb increases the output current, but the efficiency decreases. Actually, a pulsating
current flows and a voltage drop occurs due to the wiring capacitance. Determine the optimum
value by experiment.
A speed-up capacitor (Cb) connected in parallel with Rb resistance as shown in Figure 11
decreases the switching loss and improves the efficiency.
Select Cb by observing the following equation.
Cb ≤
2
π R
b fOSC 0.7
1
However, in practice, the optimum Cb value also varies depending on the characteristics of the
bipolar transistor employed. Therefore, determine the optimum value of Cb by experiment.
相关PDF资料 |
PDF描述 |
|---|---|
| S-8338ABCA-P8T1G | 0.16 A SWITCHING CONTROLLER, 1246.3 kHz SWITCHING FREQ-MAX, PDSO8 |
| S-80132ANPF-JCRTFGG | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO4 |
| SC101R8KT | 1 ELEMENT, 1.8 uH, GENERAL PURPOSE INDUCTOR |
| SC10820KT | 1 ELEMENT, 82 uH, GENERAL PURPOSE INDUCTOR |
| SC153R9K | 1 ELEMENT, 2.3 uH, GENERAL PURPOSE INDUCTOR |
相关代理商/技术参数 |
参数描述 |
|---|---|
| S-8338ABAA-P8T1G | 制造商:Seiko Instruments Inc (SII) 功能描述: |
| S-8338ABAA-T8T1G | 制造商:Seiko Instruments Inc (SII) 功能描述: |
| S-8338ABAC-P8T1G | 制造商:Seiko Instruments Inc (SII) 功能描述:STEPUP1.2MHZ PWM SWR |
| S-8338ABCA-P8T1G | 制造商:Seiko Instruments Inc (SII) 功能描述:STEPUP1.2MHZ PWM SWR |
| S-8338ABCB-P8T1G | 制造商:Seiko Instruments Inc (SII) 功能描述:STEPUP1.2MHZ PWM SWR |
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