参数资料
| 型号： | LTC3730CG#TR |
| 厂商： | Linear Technology |
| 文件页数： | 21/28页 |
| 文件大小： | 0K |
| 描述： | IC CTRLR BUCK POLYPHASE 36-SSOP |
| 标准包装： | 2,000 |
| 应用： | 控制器，Intel 移动式 VID |
| 输入电压： | 4 V ~ 36 V |
| 输出数： | 1 |
| 输出电压： | 0.6 V ~ 1.75 V |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 36-SSOP（0.209"，5.30mm 宽） |
| 供应商设备封装： | 36-SSOP |
| 包装： | 带卷 (TR) |
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LTC3730
APPLICATIO S I FOR ATIO
Automotive Considerations: Plugging into the
Cigarette Lighter
voltage. Apply a 400kHz signal into the PLLIN pin or apply
1.2V to the PLLFLTR pin.
V OUT ? V OUT ?
? 1 ?
( )
?
? 1 ?
(
)( )( )
20 V ?
As battery-powered devices go mobile, there is a natural
interest in plugging into the cigarette lighter in order to
conserve or even recharge battery packs during opera-
tion. But before you connect, be advised: you are plugging
into the supply from hell. The main battery line in an
automobile is the source of a number of nasty potential
transients, including load dump, reverse battery and
double battery.
L =
f ? I ? V IN ?
1 . 3 V ?
=
400 kHz 30 % 15 A ?
≥ 0 . 68 μ H
1 . 3 V ?
?
= 0 . 0037 ?
R SENSE =
15 A ? 1 +
2 ?
?
Loaddumpistheresultofaloosebatterycable.Whenthe
cable breaks connection, the field collapse in the alternator
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.
The network shown in Figure 10 is the most straightfor-
ward 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
Using L = 0.6 μ H, 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.
R SENSE1, R SENSE2 and R SENSE3 can be calculated by using
aconservativemaximumsensecurrentthresholdof65mV
and taking into account half of the ripple current:
65 mV
? 34 % ?
?
Use a commonly available 0.003 ? sense resistor.
Next verify the minimum on-time is not violated. The
minimum on-time occurs at maximum V CC :
of 32V on the SW pins, most applications will be limited to
30V by the MOSFET BV DSS .
V BAT
t ON ( MIN ) =
V OUT
V IN ( MAX ) ( f )
=
1 . 3 V
20 V ( 400 kHz )
= 162 ns
12V
The output voltage will be set by the VID code according
V CC
5V
LTC3730
+
3730 F10
to Table 1.
The power dissipation on the topside MOSFET can be
estimated. Using a Fairchild FDS6688 for example, R DS(ON)
= 7m ? , C MILLER = 15nC/15V = 1000pF. At maximum input
voltage with T(estimated) = 50 ° C:
( ) [ ( ) ( ) ]
15 1 + 0 . 005 50 ° C ? 25 ° C
( ) ( )( ) ( )(
)
2 ? 45 A ?
? 2 3 ?
( )
? 1 1 ?
? 400 kHz = 2 . 2 W
?
Figure 10. Automotive Application Protection
Design Example (Using Three Phases)
As a design example, assume V CC = 5V, V IN = 12V(nominal),
V IN = 20V(max), V OUT = 1.3V, I MAX = 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
P MAIN ≈
1 . 8 V 2
20 V
0 . 007 ? + 20 ? ? 2 ? 1000 pF
? ?
+
? 5 V – 1 . 8 V 1 . 8 V ?
3730fa
21
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| LTC3731CG | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
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