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參數(shù)資料
| 型號(hào)： | LTC3859IUHF#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PQCC38 |
| 封裝： | 5 X 7 MM, LEAD FREE, PLASTIC, MO-220WHKD, QFN-38 |
| 文件頁數(shù)： | 14/42頁 |
| 文件大?。?/td> | 624K |
| 代理商： | LTC3859IUHF#TRPBF |
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LTC3859
21
3859fa
APPLICATIONS INFORMATION
Inductor DCR Sensing
For applications requiring the highest possible efciency at
high load currents, the LTC3859 is capable of sensing the
voltagedropacrosstheinductorDCR,asshowninFigure4b.
The DCR of the inductor represents the small amount of
DC winding resistance of the copper, which can be less
than 1mΩ for today’s low value, high current inductors.
In a high current application requiring such an inductor,
conduction loss through a sense resistor would cost several
points of efciency compared to DCR sensing.
If the external R1||R2 C1 time constant is chosen to be
exactly equal to the L/DCR time constant, the voltage drop
across the external capacitor is equal to the drop across
the inductor DCR multiplied by R2/(R1 + R2). R2 scales the
voltage across the sense terminals for applications where
the DCR is greater than the target sense resistor value.
To properly dimension the external lter components, the
DCR of the inductor must be known. It can be measured
using a good RLC meter, but the DCR tolerance is not
always the same and varies with temperature; consult the
manufacturers’ data sheets for detailed information.
Using the inductor ripple current value from the Inductor
Value Calculation section, the target sense resistor value
is:
R
SENSE(EQUIV) =
V
SENSE(MAX)
I
MAX +
ΔI
L
2
To ensure that the application will deliver full load cur-
rent over the full operating temperature range, determine
RSENSE(EQUIV), keeping in mind that the maximum current
sense threshold (VSENSE(MAX)) for the LTC3859 is xed
at 50mV.
Next, determine the DCR of the inductor. Where provided,
use the manufacturer’s maximum value, usually given at
20°C. Increase this value to account for the temperature
coefcient of resistance, which is approximately 0.4%/°C.
A conservative value for TL(MAX) is 100°C.
To scale the maximum inductor DCR to the desired sense
resistor value, use the divider ratio:
R
D =
R
SENSE(EQUIV)
DCR
MAX at TL(MAX)
C1 is usually selected to be in the range of 0.1μF to 0.47μF.
This forces R1||R2 to around 2k, reducing error that might
have been caused by the SENSE+ pin’s ±1μA current.
The equivalent resistance R1||R2 is scaled to the room
temperature inductance and maximum DCR:
R1 R2
=
L
(DCR at 20
°C)C1
The sense resistor values are:
R1
=
R1 R2
R
D
;R2
=
R1 R
D
1
R
D
3859 F04a
LTC3859
INTVCC
BOOST
TG
SW
BG
SENSE1,2+
(SENSE3–)
SENSE1, 2–
(SENSE3+)
SGND
VIN1,2
(VOUT3)
VOUT1,2
(VIN3)
RSENSE
CAP
PLACED NEAR SENSE PINS
4b. Using the Inductor DCR to Sense Current
4a. Using a Resistor to Sense Current
3859 F04b
LTC3859
INTVCC
BOOST
TG
SW
BG
SENSE1, 2+
(SENSE3–)
SENSE1, 2–
(SENSE3+)
SGND
VIN1,2
(VOUT3)
VOUT1,2
(VIN3)
C1*
R2
*PLACE C1 NEAR SENSE PINS
RSENSE(EQ) = DCR(R2/(R1+R2))
L
DCR
INDUCTOR
R1
(R1||R2) C1 = L/DCR
Figure 4. Current Sensing Methods
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| LTC3860EUH#PBF | 功能描述:IC REG CTRLR BUCK PWM VM 32-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 |
| LTC3860EUH#PBF | 制造商:Linear Technology 功能描述:BUCK DC/DC CONVERTER IC |
| LTC3860EUH#TRPBF | 功能描述:IC REG CTRLR BUCK PWM VM 32-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) |
| LTC3860IUH#PBF | 功能描述:IC REG CTRLR BUCK PWM VM 32-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:2,000 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:50% 電源電壓:9 V ~ 10 V 降壓:無 升壓:是 回掃:是 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:8-TSSOP（0.173"，4.40mm 寬） 包裝:帶卷 (TR) |
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