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參數(shù)資料
| 型號： | LTC3773EUHF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 700 kHz SWITCHING FREQ-MAX, PQCC38 |
| 封裝： | 5 X 7 MM, PLASTIC, MO-220WHKD, QFN-38 |
| 文件頁數(shù)： | 10/32頁 |
| 文件大?。?/td> | 461K |
| 代理商： | LTC3773EUHF |
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LTC3773
18
3773fa
This formula has a maximum value at VIN = 2VOUT, where
IRMS = IOUT/2. This simple worst-case condition is com-
monly used for design because even signicant deviations
do not offer much relief. Note that capacitor manufacturer’s
ripple current ratings are often based on only 2000 hours
of life. This makes it advisable to further derate the capaci-
tor, or to choose a capacitor rated at a higher temperature
than required. Several capacitors may also be paralleled
to meet size or height requirements in the design. Always
consult the manufacturer if there is any question.
The benet of the LTC3773 multiphase clocking can be
calculated by using the equation above for the highest
power controller and then calculating the loss that would
have resulted if all three channels switched on at the same
time. The total RMS power lost is lower when triple control-
lers are operating due to the interleaving of current pulses
through the input capacitor’s ESR. This is why the input
capacitance requirement calculated above for the worst-
case controller is adequate for the triple controller design.
Remember that input protection fuse resistance, battery
resistance and PC board trace resistance losses are also
reduced due to the reduced peak currents in a multiphase
system. The overall benet of a multiphase design will only
be fully realized when the source impedance of the power
supply/battery is included in the efciency testing. The
drains of the three top MOSFETs should be placed within
1cm of each other and share a common CIN(s). Separating
the drains and CIN may produce undesirable voltage and
current resonances at VIN.
The selection of COUT is driven by the required effective
series resistance (ESR). Typically once the ESR require-
ment is satised the capacitance is adequate for ltering.
The output ripple (
ΔVOUT) is determined by:
V
I ESR
fC
OUT
L
OUT
≈+
1
8
Where f = operating frequency, COUT = output capacitance,
and
ΔIL= ripple current in the inductor. The output ripple is
highest at maximum input voltage since
ΔIL increases with
input voltage. With
ΔIL = 0.3IOUT(MAX) the output ripple will
typically be less than 50mV at maximum VIN assuming:
C
commended ESR
R
and C
fR
OUT
SENSE
OUT
SENSE
Re
(
)
<
>
2
1
8
The rst condition relates to the ripple current into
the ESR of the output capacitance while the second
term guarantees that the output capacitance does not
signicantly discharge during the operating frequency
period due to ripple current. The choice of using smaller
output capacitance increases the ripple voltage due to the
discharging term but can be compensated for by using
capacitors of very low ESR to maintain the ripple voltage
at or below 50mV. The ITH pin OPTI-LOOP compensation
components can be optimized to provide stable, high
performance transient response regardless of the output
capacitors selected.
Manufacturers such as Sanyo, Panasonic and Cornell
Dubilier should be considered for high performance
through-hole capacitors. The OS-CON semiconductor
electrolyte capacitor available from Sanyo has a good
(ESR)(size) product. An additional ceramic capacitor in
parallel with OS-CON capacitors is recommended to offset
the effect of lead inductance.
In surface mount applications, multiple capacitors may
have to be paralleled to meet the relevant ESR or transient
current handling requirements. Aluminum electrolytic
and dry tantalum capacitors are both available in surface
mount congurations. 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
output capacitor choices are the Sanyo POSCAP TPD, TPE,
TPF, AVX TPS, TPSV, the Kemet T510 series of surface
mount tantalums, Kemet AO-CAPs or the Panasonic SP
series of surface mount special polymer capacitors avail-
able in case heights ranging from 2mm to 4mm. Other
capacitor types include Nichicon PL series and Sprague
595D series. Consult the manufacturers for other specic
recommendations.
RSENSE Selection for Output Current
Once the frequency and inductor have been chosen, RSENSE
is determined based on the required peak inductor current.
The current comparator has a typical maximum threshold
of 75mV/RSENSE and an input common mode range of
SGND to (1.1) VCC. The current comparator threshold
sets the peak inductor current, yielding a maximum aver-
APPLICATIONS INFORMATION
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相關(guān)代理商/技術(shù)參數(shù) |
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| LTC3773EUHF#PBF | 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® 特色產(chǎn)品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標(biāo)準(zhǔn)包裝:1 系列:PowerWise® PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:81% 電源電壓:4.5 V ~ 18 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:-5°C ~ 125°C 封裝/外殼:32-WFQFN 裸露焊盤 包裝:Digi-Reel® 產(chǎn)品目錄頁面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR |
| LTC3773EUHF#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: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 |
| LTC3774EUHE#PBF | 制造商:Linear Technology 功能描述:SWITCHING REG, BUCK, ADJ, 2.2MHZ, DFN-36 |
| LTC3774IUHE#PBF | 制造商:Linear Technology 功能描述:SWITCHING REG, BUCK, ADJ, 2.2MHZ, DFN-36 |
| LTC3775EMSE#PBF | 功能描述:IC REG CTRLR BUCK PWM VM 16-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 特色產(chǎn)品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標(biāo)準(zhǔn)包裝:1 系列:PowerWise® PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:81% 電源電壓:4.5 V ~ 18 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:-5°C ~ 125°C 封裝/外殼:32-WFQFN 裸露焊盤 包裝:Digi-Reel® 產(chǎn)品目錄頁面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR |
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