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參數(shù)資料
| 型號： | LTC3851AMPMSE#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING REGULATOR, PDSO16 |
| 封裝： | LEAD FREE, PLASTIC, MSOP-16 |
| 文件頁數(shù)： | 17/30頁 |
| 文件大?。?/td> | 430K |
| 代理商： | LTC3851AMPMSE#PBF |
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LTC3851A
24
3851afa
Design Example
As a design example, assume VIN = 12V (nominal), VIN =
22V (maximum), VOUT = 1.8V, IMAX = 5A, and f = 250kHz.
Refer to Figure 13.
The inductance value is chosen first based on a 30%
ripple current assumption. The highest value of ripple
current occurs at the maximum input voltage. Connect a
160k resistor between the FREQ/PLLFLTR and GND pins,
generating 250kHz operation. The minimum inductance
for 30% ripple current is:
ΔIL =
1
f
( ) L()
VOUT 1
VOUT
VIN
A 4.7H inductor will produce 28% ripple current and a
3.3H will result in 40%. The peak inductor current will be
the maximum DC value plus one-half the ripple current, or
6A, for the 3.3H value. Increasing the ripple current will
also help ensure that the minimum on-time of 90ns is not
violated. The minimum on-time occurs at maximum VIN:
tON(MIN) =
VOUT
VIN(MAX) f
( )
=
1.8V
22V 250kHz
(
)
= 327ns
The RSENSE resistor value can be calculated by connect-
ing ILIM to INTVCC and using the maximum current sense
voltage specification with some accommodation for toler-
ances. Tie ILIM to INTVCC.
RSENSE ≤
75mV
6A
= 0.0125Ω, so 0.01Ω is selected
Choosing 1% resistors: R1 = 25.5k and R2 = 32.4k yields
an output voltage of 1.816V.
applicaTions inForMaTion
ThepowerdissipationonthetopsideMOSFETcanbeeasily
estimated. Choosing a Fairchild FDS6982S dual MOSFET
results in: RDS(ON) = 0.035/0.022, CMILLER = 215pF. At
maximum input voltage with T (estimated) = 50°C:
PMAIN =
1.8V
22V
5
( )2 1+ 0.005
(
) 50°C25°C
(
)
0.035
Ω
(
)+ 22V
( )2
5A
2
2Ω
( ) 215pF
(
)
1
5
2.3
+
1
2.3
250kHz
(
) = 185mW
A short circuit to ground will result in a folded back cur-
rent of:
ISC =
29mV
0.0125
Ω
– 1
2
90ns 22V
( )
3.3H
= 2.02A
with a typical value of RDS(ON) and δ = (0.005/°C)(25°C)
= 0.125. The resulting power dissipated in the bottom
MOSFET is:
PSYNC =
22V
2.02A
(
)2 1.125
(
) 0.022Ω
(
)
= 101.0mW
which is less than under full-load conditions.
CIN is chosen for an RMS current rating of at least 3A at
temperature. COUT is chosen with an ESR of 0.02 for
low output ripple. The output ripple in continuous mode
will be highest at the maximum input voltage. The output
voltage ripple due to ESR is approximately:
VORIPPLE = RESR (IL) = 0.02 (2A) = 40mVP-P
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
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| LTC3851EGN#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP 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 標準包裝: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 |
| LTC3851EGN#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝: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) |
| LTC3851EMSE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 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 標準包裝: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 |
| LTC3851EMSE#PBF | 制造商:Linear Technology 功能描述:Switch Regulator IC 制造商:Linear Technology 功能描述:IC SYNC STEP-DOWN REGULATOR CTRL MSOP-16 |
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