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| 型号： | LTC3407EDD#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 12/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 1A DL 10DFN |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 2 |
| 输出电压： | 0.6 V ~ 5 V |
| 输入电压： | 2.5 V ~ 5.5 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 1.5MHz |
| 电流 - 输出： | 1A |
| 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： | 10-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 10-DFN（3x3） |
LTC3407
APPLICATIONS INFORMATION
the regulator operating in a 70°C ambient temperature is
approximately:
T J = 2 ? 0.153 ? 45 + 70 = 84°C
which is below the absolute maximum junction tempera-
ture of 125°C.
Design Example
As a design example, consider using the LTC3407 in an
portable application with a Li-Ion battery. The battery pro-
vides a V IN = 2.8V to 4.2V. The load requires a maximum
of 600mA in active mode and 2mA in standby mode. The
output voltage is V OUT = 2.5V. Since the load still needs
power in standby, Burst Mode operation is selected for
good low load ef?ciency.
First, calculate the inductor value for about 30% ripple
current at maximum V IN :
2.5V ? 2.5V ?
L ≥ ? ? 1 – ? = 2.25 μ H
1.5MHz ? 300mA ? 4.2V ?
Choosing the closest inductor from a vendor of 2.2μH
inductor, results in a maximum ripple current of:
2.5V ? 2.5V ?
Δ I L = ? ? 1 ? ? = 307mA
1.5MHz ? 2.2 μ H ? 4.2V ?
For cost reasons, a ceramic capacitor will be used. C OUT
selection is then based on load step droop instead of ESR
requirements. For a 5% output droop:
Board Layout Considerations
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of
the LTC3407. These items are also illustrated graphically
in the layout diagram of Figure 3. Check the following in
your layout:
1. Does the capacitor C IN connect to the power V IN (Pin
3) and GND (exposed pad) as close as possible? This
capacitor provides the AC current to the internal power
MOSFETs and their drivers.
2. Are the C OUT and L1 closely connected? The (–) plate of
C OUT returns current to GND and the (–) plate of C IN .
3. The resistor divider, R1 and R2, must be connected
between the (+) plate of C OUT and a ground sense line
terminated near GND (Exposed Pad). The feedback signals
V FB should be routed away from noisy components and
traces, such as the SW line (Pins 4 and 7), and its trace
should be minimized.
4. Keep sensitive components away from the SW pins. The
input capacitor C IN and the resistors R1 to R4 should be
routed away from the SW traces and the inductors.
5. A ground plane is preferred, but if not available, keep
the signal and power grounds segregated with small signal
components returning to the GND pin at one point and
should not share the high current path of C IN or C OUT .
6. Flood all unused areas on all layers with copper. Flood-
C OUT ≈ 3
600mA
1.5MHz ? (5% ? 2.5V)
= 9.6 μ F
ing with copper will reduce the temperature rise of power
components. These copper areas should be connected to
V IN or GND.
The closest standard value is 10μF. Since the output imped-
ance of a Li-Ion battery is very low, C IN is typically 10μF.
The output voltage can now be programmed by choosing
V IN
C IN
RUN2 V IN
MODE/SYNC
RUN1
POR
the values of R1 and R2. To maintain high ef?ciency, the
LTC3407
current in these resistors should be kept small. Choosing
2μA with the 0.6V feedback voltage makes R1~300k. A close
V OUT2
C5
L2
SW2
SW1
L1
C4
V OUT1
standard 1% resistor is 280k, and R2 is then 887k.
The POR pin is a common drain output and requires a pull-
up resistor. A 100k resistor is used for adequate speed.
C OUT2
R4
R3
V FB2
GND
V FB1
R1
R2
C OUT1
Figure 1 shows the complete schematic for this design
example.
BOLD LINES INDICATE HIGH CURRENT PATHS
3407 F03
Figure 3. LTC3407 Layout Diagram (See Board Layout Checklist)
3407fa
12
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| LTC3407EMSE | 功能描述:IC REG BUCK SYNC ADJ 1A 10MSOP RoHS:否 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 |
| LTC3407EMSE#PBF | 功能描述:IC REG BUCK SYNC ADJ 1A 10MSOP 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 |
| LTC3407EMSE#TR | 功能描述:IC REG BUCK SYNC ADJ 1A 10MSOP RoHS:否 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 |
| LTC3407EMSE#TRPBF | 功能描述:IC REG BUCK SYNC ADJ 1A 10MSOP 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 |
| LTC3407EMSE-2 | 制造商:Linear Technology 功能描述:Conv DC-DC Dual Step Down 2.5V to 5.5V 10-Pin MSOP EP |
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