參數(shù)資料
型號(hào)： S-8520A33MC-AVS-T2
英文描述： Analog IC
中文描述： 模擬IC
文件頁(yè)數(shù)： 12/37頁(yè)
文件大?。?/td> 599K
代理商： S-8520A33MC-AVS-T2
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
Seiko Instruments Inc.
12
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
μ
F to 100
μ
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
μ
F to 100
μ
F can serve as a rough yardstick for this
selection.
5.
External Switching Transistor
The S-8520/21 Series can be operated with an external switching transistor of the enhancement (Pch)
MOS FET type or bipolar (PNP) typ.
5.1 Enhancement MOS FET type
The EXT pin of the S-8520/21 Series is capable of directly driving a Pch power MOS FET with a gate
capacity of some 1000 pF.
When a Pch power MOS FET is chosen, because it has a higher switching speed than a PNP type
bipolar transistor and because power losses due to the presence of a base current are avoided,
efficiency will be 2% to 3% higher than when other types of transistor are employed.
The important parameters to be kept in mind in selecting a Pch power MOS FET include the threshold
voltage, breakdown voltage between gate and source, breakdown voltage between drain and source,
total gate capacity, on-resistance, and the current rating.
The EXT pin swings from voltage VIN over to voltage Vss. If the input voltage is low, a MOS FET with a
low threshold voltage has to be used so that the MOS FET will come on as required. If, conversely, the
input voltage is high, select a MOS FET whose gate-source breakdown voltage is higher than the input
voltage by at least several volts.
Immediately after the power is turned on, or when the power is turned off (that is, when the step-down
operation is terminated), the input voltage will be imposed across the drain and the source of the MOS
FET. Therefore, the transistor needs to have a drain-source breakdown voltage that is also several
volts higher than the input voltage.
The total gate capacity and the on-resistance affect the efficiency.
The power loss for charging and discharging the gate capacity by switching operation will increase,
when the total gate capacity becomes larger and the input voltage rises higher. Therefore the gate
capacity affects the efficiency of power in a low load current region. If the efficiency under light loads is
a matter of particular concern, select a MOS FET with a small total gate capacity.
In regions where the load current is high, the efficiency is affected by power losses caused due to the
on-resistance of the MOS FET. Therefore, if the efficiency under heavy loads is particularly important
for your application, choose a MOS FET with as low an on-resistance as possible.
As for the current rating, select a MOS FET whose maximum continuous drain current rating is higher
than the peak current Ipk.
相關(guān)PDF資料
PDF描述
S-8520A50MC-AWJ-T2 Analog IC
S-8520B25MC-ARK-T2 Analog IC
S-8520B30MC-ARP-T2 Analog IC
S-8520B33MC-ARS-T2 Analog IC
S-8520B50MC-ASJ-T2 Analog IC
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
S-8520A33MC-AVST2G 功能描述:DC/DC 開(kāi)關(guān)控制器 3.3V Step-Down PWM RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)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-8520A34MC-ART-T2 制造商:SII 制造商全稱:Seiko Instruments Inc 功能描述:PWM CONTROL & PWM/PFM CONTROL STEP-DOWN SWITCHING REGULATOR-CONTROLLERS
S-8520A34MC-AVT-T2 功能描述:DC/DC 開(kāi)關(guān)控制器 3.4V Step-Down PWM RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)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-8520A34MC-AVTT2G 功能描述:DC/DC 開(kāi)關(guān)控制器 3.4V Step-Down PWM RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)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-8520A34MC-AVTT2U 功能描述:IC REG CTRLR BUCK SOT23-5 制造商:ablic u.s.a. inc. 系列:- 包裝:剪切帶（CT） 零件狀態(tài):在售 輸出類型:晶體管驅(qū)動(dòng)器 功能:降壓 輸出配置:正 拓?fù)?降壓 輸出數(shù):1 輸出階段:1 電壓 - 電源（Vcc/Vdd）:2.5 V ~ 10 V 頻率 - 開(kāi)關(guān):180kHz 占空比（最大）:1 同步整流器:無(wú) 時(shí)鐘同步:無(wú) 串行接口:- 控制特性:使能 工作溫度:-40°C ~ 85°C（TA） 封裝/外殼:SC-74A，SOT-753 供應(yīng)商器件封裝:SOT-23-5 標(biāo)準(zhǔn)包裝:1
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。

采購(gòu)需求

(若只采購(gòu)一條型號(hào)，填寫(xiě)一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

*型號(hào) *數(shù)量 廠商 批號(hào) 封裝
添加更多采購(gòu)

我的聯(lián)系方式

*
*
*