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參數(shù)資料
| 型號： | LTC3731HUH#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 5 A SWITCHING CONTROLLER, 750 kHz SWITCHING FREQ-MAX, PQCC32 |
| 封裝： | 5 X 5 MM, LEAD FREE, PLASTIC, MO-220WHHD, QFN-32 |
| 文件頁數(shù)： | 15/34頁 |
| 文件大小： | 427K |
| 代理商： | LTC3731HUH#PBF |
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LTC3731H
3731Hfb
applicaTions inForMaTion
Automotive Considerations: Plugging into the
Cigarette Lighter
As battery-powered devices go mobile, there is a natural
interest in plugging into the cigarette lighter in order to
conserveorevenrechargebatterypacksduringoperation.
But before you connect, be advised: you are plugging into
thesupplyfromhell.Themainbatterylineinanautomobile
is the source of a number of nasty potential transients, in-
cluding load dump, reverse battery and double battery.
Load dump is the result of a loose battery cable. When the
cable breaks connection, the field collapse in the alterna-
tor can cause a positive spike as high as 60V which takes
several hundred milliseconds to decay. Reverse battery is
just what it says, while double battery is a consequence of
tow-truck operators finding that a 24V jump start cranks
cold engines faster than 12V.
ThenetworkshowninFigure10isthemoststraightforward
approach to protect a DC/DC converter from the ravages
of an automotive battery line. The series diode prevents
current from flowing during reverse battery, while the
transient suppressor clamps the input voltage during
load dump. Note that the transient suppressor should not
conduct during double-battery operation, but must still
clamp the input voltage below breakdown of the converter.
Although the IC has a maximum input voltage of 32V on
the SW pins, most applications will be limited to 30V by
the MOSFET BVDSS.
Design Example
Asadesignexample,assumeVCC=5V,VIN=12V(nominal),
VIN = 20V(max), VOUT = 1.3V, IMAX = 45A and f = 400kHz.
The inductance value is chosen first based upon a 30%
ripple current assumption. The highest value of ripple
current in each output stage occurs at the maximum
input voltage.
L
V
f I
V
kHz
OUT
IN
=
( )
= (
)(
1
1 3
400
30
.
%
))( )
≥
15
1
1 3
20
0 68
A
V
H
.
Using L = 0.6H, a commonly available value results in
34% ripple current. The worst-case output ripple for the
three stages operating in parallel will be less than 11% of
the peak output current.
RSENSE1, RSENSE2 and RSENSE3 can be calculated by using
aconservativemaximumsensecurrentthresholdof65mV
and taking into account half of the ripple current:
R
mV
A
SENSE =
+
=
65
15 1 34
2
0 0037
%
.
Use a commonly available 0.003Ω sense resistor.
Next verify the minimum on-time is not violated. The
minimum on-time occurs at maximum VCC:
t
V
f
V
kHz
ns
ON MIN
OUT
IN MAX
( ) =
( )
=
(
)
=
(
)
.
1 3
20 400
162
The output voltage will be set by the resistive divider from
the DIFFOUT pin to SGND, R1 and R2 in the Functional
Diagram. Set R1 = 13.3k and R2 = 11.3k.
Figure 10. Automotive Application Protection
+
LTC3731H
VCC
5V
VBAT
12V
3731H F10
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC3731IG | 制造商:Linear Technology 功能描述:LDO Cntrlr SYNC BUCK REG 0.6V to 6V 36-Pin SSOP |
| LTC3731IG#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP 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 |
| LTC3731IG#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP 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 |
| LTC3731IUH | 制造商:Linear Technology 功能描述:LDO Cntrlr SYNC BUCK REG 0.6V to 6V 32-Pin QFN EP |
| LTC3731IUH#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 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: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 |
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