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參數(shù)資料
| 型號： | LTC3618EFE#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 8 A DUAL SWITCHING CONTROLLER, 2700 kHz SWITCHING FREQ-MAX, PDSO24 |
| 封裝： | 4.40 MM, LEAD FREE, PLASTIC, TSSOP-24 |
| 文件頁數(shù)： | 11/24頁 |
| 文件大?。?/td> | 603K |
| 代理商： | LTC3618EFE#TRPBF |
LTC3618
19
3618f
2. I2R losses are calculated from the resistances of the
internal switches, RSW, and external inductor RL. In
continuous mode the average output current owing
through inductor L is “chopped” between the main
switch and the synchronous switch. Thus, the series
resistance looking into the SW pin is a function of both
top and bottom MOSFET RDS(ON) and the duty cycle
(DC), as follows:
RSW = (RDS(ON)TOP)(DC) + (RDS(ON)BOT)(1 – DC)
The RDS(ON) for both the top and bottom MOSFETs can
be obtained from the Typical Performance Characteristics
curves. To obtain I2R losses, simply add RSW to RL and
multiply the result by the square of the average output
current.
Other losses, including CINandCOUTESRdissipativelosses
and inductor core losses, generally account for less than
2% of the total loss.
Thermal Considerations
In most applications, the LTC3618 does not dissipate
much heat due to its high efciency. However, in ap-
plications where the LTC3618 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 160°C, all four power
switches will be turned off and the SW node will become
high impedance.
To prevent the LTC3618 from exceeding the maximum
junction temperature, the user will need to do some ther-
mal analysis 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 = TA + TRISE
where TA is the ambient temperature.
As an example, consider this case: the LTC3618 is in
dropout at an input voltage of 3.3V with a load current for
each channel of 2A at an ambient temperature of 70°C.
Assuming a 20°C rise in junction temperature, to 90°C,
results in an RDS(ON) of 0.086mΩ (see the graph in the
Typical Performance Characteristics section). Therefore,
the power dissipated by the part is:
PD = (I12 + I22) RDS(ON) = 0.69W
For the QFN package, the
θJA is 37°C/W.
Therefore, the junction temperature of the regulator op-
erating at 70°C ambient temperature is approximately:
TJ = 0.69W 37°C/W + 70°C = 95°C
Note that for very low input voltage, the junction tem-
perature will be higher due to increased switch resistance
RDS(ON). It is not recommended to use full load current at
high ambient temperature and low input voltage.
To maximize the thermal performance of the LTC3618, the
exposed pad should be soldered to a ground plane. See
the PC Board Layout Checklist.
Design Example
As a design example, consider using the LTC3618 in an
application with the following specications:
VIN = 3.3V to 5.5V
VDDQ = 1.8V
VTT = 0.9V
IOUT1(MAX) = 3A
IOUT2(MAX) = 3A
IOUT1(MIN) = 200mA
f = 2.25MHz
First, calculate the timing resistor:
RRT =
4 1011
Ω Hz
2.25MHz
= 178k
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| LTC3618EUF#PBF | 功能描述:IC REG DUAL SYNC 3A BUCK 24QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標(biāo)準(zhǔn)包裝:43 系列:- 應(yīng)用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:48-QFN（7x7） 包裝:管件 |
| LTC3618EUF#TRPBF | 功能描述:IC REG DUAL SYNC 3A BUCK 24QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標(biāo)準(zhǔn)包裝:43 系列:- 應(yīng)用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:48-QFN（7x7） 包裝:管件 |
| LTC3618IFE#PBF | 功能描述:IC REG DUAL SYNC 3A BUCK 24TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標(biāo)準(zhǔn)包裝:43 系列:- 應(yīng)用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:48-QFN（7x7） 包裝:管件 |
| LTC3618IFE#TRPBF | 功能描述:IC REG DUAL SYNC 3A BUCK 24TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標(biāo)準(zhǔn)包裝:43 系列:- 應(yīng)用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:48-QFN（7x7） 包裝:管件 |
| LTC3618IUF#PBF | 功能描述:IC REG DUAL SYNC 3A BUCK 24QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標(biāo)準(zhǔn)包裝:43 系列:- 應(yīng)用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:48-QFN（7x7） 包裝:管件 |
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