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| 型号： | LTC3417AIFE-1#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 15/20页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ DL 20TSSOP |
| 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： | 0.8 V ~ 5 V |
| 输入电压： | 2.25 V ~ 5.5 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 1.5MHz，600kHz ~ 4MHz |
| 电流 - 输出： | 1A，1.5A |
| 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： | 20-TSSOP（0.173"，4.40mm 宽）裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 20-TSSOP-EP |
LTC3417A-1
APPLICATIONS INFORMATION
Although all dissipative elements in the circuit produce
losses, four main sources account for most of the losses
in LTC3417A-1 circuits: 1) LTC3417A-1 I S current, 2)
switching losses, 3) I 2 R losses, 4) other losses.
1) The I S current is the DC supply current given in the elec-
trical characteristics which excludes MOSFET driver and
control currents. I S current results in a small (< 0.1%)
loss that increases with V IN , even at no load.
2) The switching current is the sum of the MOSFET driver
and control currents. The MOSFET driver current re-
sults from switching the gate capacitance of the power
MOSFETs. Each time a MOSFET gate is switched from
low to high to low again, a packet of charge moves from
V IN to ground. The resulting charge over the switching
period is a current out of V IN that is typically much larger
than the DC bias current. The gate charge losses are
proportional to V IN and thus their effects will be more
pronounced at higher supply voltages.
3) I 2 R losses are calculated from the DC resistances of the
internal switches, R SW , and the external inductor, R L . In
continuous mode, the average output current ?owing
through inductor L is “chopped” between the internal
top and bottom switches. Thus, the series resistance
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 Characteristics
curves. Thus, to obtain I 2 R losses:
I 2 R losses = I OUT2 (R SW + R L )
where R L is the resistance of the inductor.
4) Other “hidden” losses such as copper trace and internal
battery resistances can account for additional ef?ciency
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 COUT at
the switching frequency. Other losses including diode
conduction losses during dead-time and inductor core
losses generally account for less than 2% total additional
loss.
Thermal Considerations
The LTC3417A-1 requires the package Exposed Pad
(PGND2/GNDD pin) to be well soldered to the PC board.
This gives the DFN and TSSOP packages exceptional
thermal properties, compared to similar packages of this
size, making it dif?cult in normal operation to exceed the
maximum junction temperature of the part. In a majority
of applications, the LTC3417A-1 does not dissipate much
heat due to its high ef?ciency. However, in applications
where the LTC3417A-1 is running at high ambient tem-
perature 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 switches
in both regulators will be turned off and the SW nodes will
become high impedance.
To prevent the LTC3417A-1 from exceeding its 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:
T RISE = P D ? θ JA
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.
The junction temperature, T J , is given by:
T J = T RISE + T AMBIENT
As an example, consider the case when the LTC3417A-1
is in dropout in both regulators at an input voltage of 3.3V
with load currents of 1.5A and 1A. From the Typical Per-
formance Characteristics graph of Switch Resistance, the
R DS(ON) resistance of the 1.5A P-channel switch is 0.09Ω
and the R DS(ON) of the 1A P-channel switch is 0.163Ω.
3417a1fa
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3417AIFE-2#PBF | 功能描述:IC REG BUCK SYNC ADJ DL 20TSSOP 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:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 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:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
| LTC3417AIFE-2#TRPBF | 功能描述:IC REG BUCK SYNC ADJ DL 20TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 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:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LTC3417AIFE-2-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Synchronous 1.5A/1A 4MHz Step-Down DC/DC Regulator |
| LTC3417AIFE-2-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Synchronous 1.5A/1A 4MHz Step-Down DC/DC Regulator |
| LTC3417AIFEPBF | 制造商:Linear Technology 功能描述:Conv DC-DC Dual Step-Down 5.5V TSSOP20EP |
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