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參數(shù)資料
| 型號： | LTC3407AEMSE#TR |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 1.25 A DUAL SWITCHING CONTROLLER, 1800 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封裝： | PLASTIC, MSOP-10 |
| 文件頁數(shù)： | 4/16頁 |
| 文件大小： | 263K |
| 代理商： | LTC3407AEMSE#TR |
LTC3407A
12
3407af
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 0.425
. 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
provides a VIN = 2.8V to 4.2V. The load requires a maxi-
mum 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 efficiency.
First, calculate the inductor value for about 30% ripple
current at maximum VIN:
L
V
MHz
mA
V
H
=
=
25
1 5
300
1
25
42
225
.
–
.
APPLICATIO S I FOR ATIO
WU
U
the SW pin is a function of both top and bottom MOSFET
RDS(ON) and the duty cycle (D) as follows:
RSW = (RDS(ON)TOP)(D) + (RDS(ON)BOT)(1 – D)
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 efficiency
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 ac-
count 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 efficiency. 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 tempera-
ture rise is given by:
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| LTC3407AEMSE-TRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Dual Synchronous 600mA, 1.5MHz Step-Down DC/DC Regulator |
| LTC3407AIDD#PBF | 功能描述:IC REG BUCK SYNC ADJ 1A DL 10DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤 |
| LTC3407AIDD#TRPBF | 功能描述:IC REG BUCK SYNC ADJ 1A DL 10DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤 |
| LTC3407AIDD-2 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Dual Synchronous 800mA,2.25MHz Step-Down DC/DC Regulator |
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