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| 型号： | LT3640EFE#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 3.4 A DUAL SWITCHING CONTROLLER, 2350 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封装： | 4.40 MM, LEAD FREE, PLASTIC, TSSOP-28 |
| 文件页数： | 8/24页 |
| 文件大小： | 506K |
| 代理商： | LT3640EFE#PBF |
LT3640
3640f
BST and SW Pin Considerations
The high voltage channel requires an external capacitor
between the BST and SW pins and an external boost diode
from a voltage source to the BST pin. In most cases, a
0.22F capacitor will work well. The (BST-SW) voltage
cannot exceed 5.5V, and must be more than 2.3V for best
efficiency. Connect the boost diode to any voltage between
2.7V and 5.5V. The VIN2 pin is the best choice if the low
voltage channel is used.
The high voltage channel will not start until the (BST-SW)
voltage is 2V or above. When the LT3640 is enabled, an
internal~5mAcurrentsourcefromVINflowsoutoftheBST
pin. The SW pin is disconnected from the SW1 pin, and is
pulled down by an internal current source to ground. The
external boost capacitor can be charged up regardless of
theoutput.Whenthe(BST-SW)voltagereaches2V,theSW
pinisconnectedtotheSW1pin,andthehighvoltagechan-
nel starts switching. However, the internal bipolar power
switchcannotbefullysaturateduntilthe(BST-SW)voltage
is further charged to above 2.3V. To start up a traditional
nonsynchronous buck regulator with very light load, the
input voltage needs to be a couple of volts higher than
the minimum running input voltage if the input voltage is
ramping up slowly. The LT3640’s unique boost capacitor
chargingschemesolvesthisstart-upissue.Figure3shows
that the minimum input voltage to start the high voltage
channel nonsynchronous buck regulator of the LT3640 is
very close to the minimum input voltage to regulate the
output voltage for most of the load range.
Soft-Start
The LT3640 has a soft-start pin for each channel. The
feedback pin voltage is regulated to the lower of the cor-
responding SS pin and the internal references, which is
1.265Vforthehighvoltagechannel,and600mVforthelow
voltage channel. A capacitor from the SS pin to ground is
charged by an internal 2A current source resulting in an
output ramping linearly from 0V to the regulated voltage.
The duration of the ramp is:
t
C
V
A
t
C
mV
A
SS
1
2
1 265
2
600
2
=
.
where tSS1 is the ramping time for the SS1 pin, tSS2 is
the ramping time for the SS2 pin, CSS1 is the capacitance
from the SS1 pin to ground, and CSS2 is the capacitance
from the SS2 pin to ground.
At power-up, a latch is set to discharge the SS1 pin.
After the SS1 pin is discharged to below 100mV, the latch
is reset. The internal 2A current source starts to charge
the SS1 pin when the (BST-SW) voltage is charged to
above 2V.
Figure 3. High Voltage Channel Minimum Input Voltage for VOUT1 = 3.3V
applicaTions inForMaTion
(3a) FS = 2MHz
(3b) FS = 500kHz
VOUT CURRENT (A)
0.001
4
V IN
VOL
TAGE
(V)
0.01
0.1
1
3
2
1
0
5
3640 F03a
START
RUN
VOUT CURRENT (A)
0.001
4
V IN
VOL
TAGE
(V)
0.01
0.1
1
3
2
1
0
5
3640 F03b
START
RUN
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3640EFETRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Monolithic Buck Regulator with Power-On Reset and Watchdog Timer |
| LT3640EUFD | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Monolithic Buck Regulator with Power-On Reset and Watchdog Timer |
| LT3640EUFD#PBF | 功能描述:IC REG BUCK FIX/ADJ DL 28QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3640EUFD#TRPBF | 功能描述:IC REG BUCK FIX/ADJ DL 28QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT3640EUFDPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Monolithic Buck Regulator with Power-On Reset and Watchdog Timer |
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