参数资料
| 型号： | LTC3561EDD#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 11/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 1A 8DFN |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.8 V ~ 5 V |
| 输入电压： | 2.63 V ~ 5.5 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 最高 4MHz |
| 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： | 8-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-DFN-EP（3x3） |
LTC3561
APPLICATIO S I FOR ATIO
looking into the SW pin is a function of both top and
bottom MOSFET R DS(ON) and the duty cycle (DC) as
follows:
R SW = (R DS(ON) TOP)(DC) + (R DS(ON) BOT)(1 – DC)
The R DS(ON) for both the top and bottom MOSFETs can
be obtained from the Typical Performance Characteris-
tics curves. Thus, to obtain I 2 R losses:
I 2 R losses = I OUT2 (R SW + R L )
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 C IN has adequate
charge storage and very low ESR at the switching
frequency. Other losses including diode conduction
losses during dead-time and inductor core losses gen-
erally account for less than 2% total additional loss.
Thermal Considerations
In a majority of applications, the LTC3561 does not dissi-
pate much heat due to its high efficiency. However, in
applications where the LTC3561 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.
As an example, consider the case when the LTC3561 is in
dropout at an input voltage of 3.3V with a load current of
1A. From the Typical Performance Characteristics graph
of Switch Resistance, the R DS(ON) resistance of the
P-channel switch is 0.11 ? . Therefore, power dissipated
by the part is:
P D = I 2 ? R DS(ON) = 110mW
The DD8 package junction-to-ambient thermal resistance,
θ JA , will be in the range of about 43 ° C/W. Therefore, the
junction temperature of the regulator operating in a 70 ° C
ambient temperature is approximately:
T J = 0.11 ? 43 + 70 = 74.7 ° C
Remembering that the above junction temperature is
obtained from an R DS(ON) at 25 ° C, we might recalculate
the junction temperature based on a higher R DS(ON) since
it increases with temperature. However, we can safely
assume that the actual junction temperature will not
exceed the absolute maximum junction temperature of
125 ° C.
Design Example
As a design example, consider using the LTC3561 in a
portable application with a Li-Ion battery (refer to Figure 4
for reference designation). The battery provides a V IN =
2.5V to 4.2V. The load requires a maximum of 1A in active
mode and 10mA in standby mode. The output voltage is
V OUT = 2.5V.
First, calculate the timing resistor:
To avoid the LTC3561 from exceeding the maximum
junction temperature, the user will need to do some
R T = 9 . 78 ? 10 11 ( 1 MHz )
? 1 . 08
= 323 . 8 k
thermal analysis. The goal of the thermal analysis is to
determine whether the power dissipated exceeds the maxi-
Use a standard value of 324k. Next, calculate the inductor
value for about 40% ripple current at maximum V IN :
? ? 1 ?
mum junction temperature of the part. The temperature
rise is given by:
T RISE = P D ? θ JA
L =
2 . 5 V ?
1 MHz ? 400 mA ?
2 . 5 V ?
4 . 2 V ? ?
= 2 . 5 μ H
where P D is the power dissipated by the regulator and θ JA
is the thermal resistance from the junction of the die to the
ambient temperature.
Choosing the closest inductor from a vendor of 2.2 μ H,
results in a maximum ripple current of:
? ? 1 ?
? = 460 mA
The junction temperature, T J , is given by:
T J = T RISE + T AMBIENT
? I L =
2 . 5 V ?
1 MHz ? 2 . 2 μ ?
2 . 5 V ?
4 . 2 V ?
3561f
11
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相关代理商/技术参数 |
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| LTC3562 | 制造商:LINER 制造商全称:Linear Technology 功能描述:I2C Quad Synchronous Step-Down DC/DC Regulator 2 × 600mA, 2 × 400mA |
| LTC3562EUD#PBF | 功能描述:IC REG BUCK SYNC ADJ QUAD 20QFN 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 |
| LTC3562EUD#TRPBF | 功能描述:IC REG BUCK SYNC ADJ QUAD 20QFN 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 |
| LTC3562EUD-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:I2C Quad Synchronous Step-Down DC/DC Regulator 2 × 600mA, 2 × 400mA |
| LTC3562EUD-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:I2C Quad Synchronous Step-Down DC/DC Regulator 2 × 600mA, 2 × 400mA |
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