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参数资料
| 型号： | SP3225ECA-L |
| 厂商： | Exar Corporation |
| 文件页数： | 4/23页 |
| 文件大小： | 0K |
| 描述： | IC TXRX RS232 ESD SD 20SSOP |
| 标准包装： | 66 |
| 类型： | 收发器 |
| 驱动器/接收器数： | 2/2 |
| 规程： | RS232 |
| 电源电压： | 3 V ~ 5.5 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-SSOP（0.209"，5.30mm 宽） |
| 供应商设备封装： | 20-SSOP |
| 包装： | 管件 |
2
Exar Corporation 48720 Kato Road, Fremont CA, 94538 50-668-707 www.exar.com
SP3224E,3225E,3226E,3227E_0_087
THEORy OF OPERATION
of5.5V,thechargepumpisenabled.Ifthe
output voltages exceed a magnitude of
5.5V,thechargepumpisdisabled.Thisos-
cillatorcontrolsthefourphasesofthevolt-
age shifting.A description of each phase
follows.
Highly Efficient Charge Pump
Thechargepumpisusedtogenerateposi-
tive and negative signal voltages for the
RS-232drivers.Thisenablesfullycompli-
antRS-232andV.28signalsfromasingle
3.0or5.5Vpowersupply.
Thechargepumpsusefourexternalcapac-
itorstoholdandtransferelectricalcharge.
The Exar patented design (US Patent
#5,306,954)usesauniqueapproachcom-
pared to older less efficient designs. The
pumps use a four–phase voltage shifting
techniquetoattainsymmetricalV+andV-
powersupplies.Anintelligentcontroloscil-
latorregulatestheoperationofthecharge
pump to maintain the proper voltages at
maximumefficiency.
Phase 1
Vss charge store and double: The posi-
tiveterminalsofcapacitorsC1andC2are
chargedfromVccwiththeirnegativetermi-
nals initially connected to ground. C1+ is
then connected to ground and the stored
charge from C1– is superimposed onto
C2–.SinceC2+isstillconnectedtoVcc
thevoltagepotentialacrosscapacitorC2is
now2xVcc.
Phase 2
Vss transfer and invert: Phase two con-
nectsthenegativeterminalofC2totheVss
storagecapacitorandthepositiveterminal
ofC2toground.Thistransfersthedoubled
andinverted(V–)voltageontoC4.Mean-
while, capacitor C1 charged from Vcc to
prepareitforitsnextphase.
Phase 3
Vddchargestoreanddouble:Phasethree
is identical to the first phase. The posi-
tiveterminalsofcapacitorsC1andC2are
chargedfromVccwiththeirnegativetermi-
nals initially connected to ground. C1+ is
then connected to ground and the stored
charge from C1– is superimposed onto
C2–. Since C2+ is still connected to Vcc
thevoltagepotentialacrosscapacitorC2is
now2xVcc.
Phase 4
Vdd transfer: The fourth phase connects
thenegativeterminalofC2togroundand
thepositiveterminalofC2totheVddstor-
age capacitor. This transfers the doubled
(V+)voltageontoC3.Meanwhile,capaci-
torC1chargedfromVcctoprepareitfor
itsnextphase.
TheExarchargepumpgeneratesV+and
V–independentlyfromVcc.Henceinano-
loadconditionV+andV-willbesymmetri-
cal. Older charge pump approaches gen-
erateV+andthenusepartofthatstored
chargetogenerateV-.Becauseofinherent
lossesthemagnitudeofV-willbesmaller
thanV+ontheseolderdesigns.
Under lightly loaded conditions the intelli-
gentpumposcillatormaximizesefficiency
byrunningonlyasneededtomaintainV+
andV–.Sinceinterfacetransceiversoften
spendmuchoftheirtimeatidlethispower-
efficientinnovationcangreatlyreducetotal
power consumption. This improvement is
madepossiblebytheindependentphase
sequenceoftheExarchargepump
design.
The clock rate for the charge pump typi-
callyoperatesatgreaterthan70kHzallow-
ing the pump to run efficiently with small
0.1μF capacitors. Efficient operation de-
pendsonrapidlycharginganddischarging
C1andC2,thereforecapacitorsshouldbe
mountedclosetotheICandhavelowESR
(equivalentseriesresistance).Inexpensive
surfacemountceramiccapacitors(suchas
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SP3225ECA-L/TR | 功能描述:RS-232接口集成电路 1MBPS+3-+5.5V RS-232 AUTO ONLINE PLUS RoHS:否 制造商:Exar 数据速率:52 Mbps 工作电源电压:5 V 电源电流:300 mA 工作温度范围:- 40 C to + 85 C 安装风格:SMD/SMT 封装 / 箱体:LQFP-100 封装: |
| SP3225ECY-L | 功能描述:RS-232接口集成电路 1MBPS+3-+5.5V RS-232 AUTO ONLINE PLUS RoHS:否 制造商:Exar 数据速率:52 Mbps 工作电源电压:5 V 电源电流:300 mA 工作温度范围:- 40 C to + 85 C 安装风格:SMD/SMT 封装 / 箱体:LQFP-100 封装: |
| SP3225ECY-L/TR | 功能描述:RS-232接口集成电路 1MBPS+3-+5.5V RS-232 AUTO ONLINE PLUS RoHS:否 制造商:Exar 数据速率:52 Mbps 工作电源电压:5 V 电源电流:300 mA 工作温度范围:- 40 C to + 85 C 安装风格:SMD/SMT 封装 / 箱体:LQFP-100 封装: |
| SP3225EEA-L | 功能描述:RS-232接口集成电路 1MBPS+3-+5.5V RS-232 AUTO ONLINE PLUS RoHS:否 制造商:Exar 数据速率:52 Mbps 工作电源电压:5 V 电源电流:300 mA 工作温度范围:- 40 C to + 85 C 安装风格:SMD/SMT 封装 / 箱体:LQFP-100 封装: |
| SP3225EEA-L/TR | 功能描述:RS-232接口集成电路 1MBPS+3-+5.5V RS-232 AUTO ONLINE PLUS RoHS:否 制造商:Exar 数据速率:52 Mbps 工作电源电压:5 V 电源电流:300 mA 工作温度范围:- 40 C to + 85 C 安装风格:SMD/SMT 封装 / 箱体:LQFP-100 封装: |
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