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参数资料
| 型号： | LTC3407AIDD#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | DUAL SWITCHING CONTROLLER, PDSO10 |
| 封装： | 3 X 3 MM, LEAD FREE, PLASTIC, MO-229WEED-2, DFN-10 |
| 文件页数： | 4/16页 |
| 文件大小： | 283K |
| 代理商： | LTC3407AIDD#PBF |
LTC3407A
12
3407afa
APPLICATIONS INFORMATION
The RDS(ON) for both the top and bottom MOSFETs can
be obtained from the Typical Performance Characteristics
curves. Thus, to obtain I2R losses:
I2R losses = IOUT2(RSW + RL)
4) Other ‘hidden’ losses such as copper trace and internal
battery resistances can account for additional efciency
degradations in portable systems. It is very important
to include these “system” level losses in the design of a
system. The internal battery and fuse resistance losses
can be minimized by making sure that CIN has adequate
charge storage and very low ESR at the switching fre-
quency. Other losses including diode conduction losses
during dead-time and inductor core losses generally
account for less than 2% total additional loss.
Thermal Considerations
In a majority of applications, the LTC3407A does not
dissipate much heat due to its high efciency. However,
in applications where the LTC3407A is running at high
ambient temperature with low supply voltage and high
duty cycles, such as in dropout, the heat dissipated may
exceed the maximum junction temperature of the part. If
the junction temperature reaches approximately 150°C,
both power switches will be turned off and the SW node
will become high impedance.
To prevent the LTC3407A from exceeding the maximum
junction temperature, the user will need to do some thermal
analysis. The goal of the thermal analysis is to determine
whether the power dissipated exceeds the maximum
junction temperature of the part. The temperature rise is
given by:
TRISE = PD θJA
where PD is the power dissipated by the regulator and θJA
is the thermal resistance from the junction of the die to
the ambient temperature.
The junction temperature, TJ, is given by:
TJ = TRISE + TAMBIENT
As an example, consider the case when the LTC3407A is
in dropout on both channels at an input voltage of 2.7V
with a load current of 600mA and an ambient temperature
of 70°C. From the Typical Performance Characteristics
graph of Switch Resistance, the RDS(ON) resistance of
the main switch is 0.425Ω. Therefore, power dissipated
by each channel is:
PD = I2 RDS(ON) = 153mW
The MS package junction-to-ambient thermal resistance,
θJA, is 45°C/W. Therefore, the junction temperature of
the regulator operating in a 70°C ambient temperature is
approximately:
TJ = 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 LTC3407A in a
portable application with a Li-Ion battery. The battery pro-
vides a VIN = 2.8V to 4.2V. The load requires a maximum
of 600mA in active mode and 2mA in standby mode. The
output voltage is VOUT = 2.5V. Since the load still needs
power in standby, Burst Mode operation is selected for
good low load efciency.
First, calculate the inductor value for about 30% ripple
current at maximum VIN:
L =
2.5V
1.5MHz 300mA
1– 2.5V
4.2V
= 2.25μH
Choosing the closest inductor from a vendor of 2.2μH
inductor, results in a maximum ripple current of:
IL =
2.5V
1.5MHz 2.2μH
1 2.5V
4.2V
= 307mA
For cost reasons, a ceramic capacitor will be used. COUT
selection is then based on load step droop instead of ESR
requirements. For a 5% output droop:
COUT ≈3
600mA
1.5MHz (5% 2.5V)
=
9.6μF
The closest standard value is 10μF. Since the output imped-
ance of a Li-Ion battery is very low, CIN is typically 10μF.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3407AIDD-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Synchronous 600mA, 1.5MHz Step-Down DC/DC Regulator |
| LTC3407AIMSE#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 |
| LTC3407AIMSE#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 |
| LTC3407AIMSE-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 |
| LTC3407AIMSE-2#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 |
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