參數(shù)資料
型號(hào)： LTC3856EFE#PBF
廠商： LINEAR TECHNOLOGY CORP
元件分類： 穩(wěn)壓器
英文描述： SWITCHING CONTROLLER, PDSO38
封裝： 4.4 MM, LEAD FREE, PLASTIC, TSSOP-38
文件頁(yè)數(shù)： 17/40頁(yè)
文件大?。?/td> 2222K
代理商： LTC3856EFE#PBF
LTC3856
3856f
applicaTions inForMaTion
reduced by the reduction of the input ripple current in a
PolyPhase system. The required amount of input capaci-
tance is further reduced by the factor N, due to the effective
increase in the frequency of the current pulses. Ceramic
capacitors are becoming very popular for small designs
but several cautions should be observed. X7R, X5R and
Y5V are examples of a few of the ceramic materials used
as the dielectric layer, and these different dielectrics have
very different effect on the capacitance value due to the
voltage and temperature conditions applied. Physically,
if the capacitance value changes due to applied voltage
change, there is a concomitant piezo effect which results
in radiating sound! A load that draws varying current at an
audible rate may cause an attendant varying input voltage
on a ceramic capacitor, resulting in an audible signal. A
secondary issue relates to the energy flowing back into
a ceramic capacitor whose capacitance value is being
reducedbytheincreasingcharge.Thevoltagecanincrease
ataconsiderablyhigherratethantheconstantcurrentbeing
supplied because the capacitance value is decreasing as
thevoltageisincreasing!Nevertheless,ceramiccapacitors,
when properly selected and used, can provide the lowest
overall loss due to their extremely low ESR.
The selection of COUT is driven by the required effective
seriesresistance(ESR).TypicallyoncetheESRrequirement
is satisfied the capacitance is adequate for filtering. The
steady-state output ripple (
VOUT) is determined by:
V
I
ESR
NfC
OUT
RIPPLE
OUT
≈
+
1
8
where f = operating frequency of each stage, N = the
number of output stages, COUT = output capacitance and
IL = ripple current in each inductor. The output ripple is
highestatmaximuminputvoltagesince
ILincreaseswith
input voltage. The output ripple will be less than 50mV at
maximum VIN with IL = 0.4IOUT(MAX) assuming:
COUT required ESR < N RSENSE
and
C
Nf R
OUT
SENSE
> ( )(
)
1
8
TheemergenceofverylowESRcapacitorsinsmall,surface
mount packages makes very small physical implementa-
tions possible. The ability to externally compensate the
switching regulator loop using the ITH pin allows a much
wider selection of output capacitor types. The impedance
characteristic of each capacitor type is significantly differ-
ent than an ideal capacitor and therefore requires accurate
modelingorbenchevaluationduringdesign.Manufacturers
suchasNichicon,NipponChemi-ConandSanyoshouldbe
consideredforhighperformancethrough-holecapacitors.
TheOS-CONsemiconductordielectriccapacitorsavailable
from Sanyo and the Panasonic SP surface mount types
have a good (ESR)(size) product.
Once the ESR requirement for COUT has been met, the
RMS current rating generally far exceeds the IRIPPLE(P-P)
requirement. Ceramic capacitors from AVX, Taiyo Yuden
and Murata offer high capacitance value and very low ESR,
especially applicable for low output voltage applications.
In surface mount applications, multiple capacitors may
have to be paralleled to meet the ESR or RMS current
handling requirements of the application. Aluminum
electrolytic and dry tantalum capacitors are both available
in surface mount configurations. New special polymer
surface mount capacitors offer very low ESR also but
have much lower capacitive density per unit volume. In
the case of tantalum, it is critical that the capacitors are
surge tested for use in switching power supplies. Several
excellent choices are the AVX TPS, AVX TPSV, the KEMET
T510 series of surface mount tantalums or the Panasonic
SP series of surface mount special polymer capacitors
availableincaseheightsrangingfrom2mmto4mm.Other
capacitor types include Sanyo POSCAP, Sanyo OS-CON,
Nichicon PL series and Sprague 595D series. Consult the
manufacturers for other specific recommendations.
Differential Amplifier
The LTC3856 has a true remote voltage sense capability.
The sensing connections should be returned from the
load, back to the differential amplifier’s inputs through a
common, tightly coupled pair of PC traces. The differential
amplifier rejects common mode signals capacitively or
inductively radiated into the feedback PC traces as well as
groundloopdisturbances.Thedifferentialamplifieroutput
signal is divided by a pair of resistors and is compared
with the internal, precision 0.6V voltage reference by the
相關(guān)PDF資料
PDF描述
LTC3856IUH#TRPBF SWITCHING CONTROLLER, PQCC38
LTC3856EFE#TRPBF SWITCHING CONTROLLER, PDSO38
LTC3860IUH#PBF DUAL SWITCHING CONTROLLER, 1250 kHz SWITCHING FREQ-MAX, PQCC32
LTC3862HUH#TRPBF DUAL SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, QCC24
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LTC3856EUH#PBF 功能描述:IC REG CTRLR BUCK PWM CM 32WFQFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR)
LTC3856EUH#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 38-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR)
LTC3856IFE#PBF 功能描述:IC REG CTRLR BUCK PWM CM 38TFSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
LTC3856IFE#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 38TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
LTC3856IUH#PBF 功能描述:IC REG CTRLR BUCK PWM CM 32WFQFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR)
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