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参数资料
| 型号： | LP3946ILD |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 电源管理 |
| 英文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO14 |
| 文件页数： | 6/15页 |
| 文件大小： | 337K |
| 代理商： | LP3946ILD |
Application Notes (Continued)
THERMAL PERFORMANCE OF LLP PACKAGE
The LP3945 and LP3946 are monolithic devices with inte-
grated pass transistors. To enhance the power dissipation
performance, the Leadless Lead frame Package, or LLP, is
used. The LLP package is designed for improved thermal
performance because of the exposed die attach pad at the
bottom center of the package. It brings advantage to thermal
performance by creating a very direct path for thermal dissi-
pation. Compared to the traditional leaded packages where
the die attach pad is embedded inside the mold compound,
the LLP reduces a layer of thermal path.
The thermal advantage of the LLP package is fully realized
only when the exposed die attach pad is soldered down to a
thermal land on the PCB board and thermal vias are planted
underneath the thermal land. Based on a LLP thermal mea-
surement, junction to ambient thermal resistance (
θ
JA) can
be improved by as much as two times if a LLP is soldered on
the board with thermal land and thermal vias than if not.
An example of how to calculate for LLP thermal performance
is shown below:
By substituting 37C/W for
θ
JA, 125C for TJ and 70C for TA,
the maximum power dissipation allowed from the chip is
1.48W at T
A = 70C. If VCHG-IN is at 5.0V and a 3.0V battery
is being charged, then 740 mA of I
CHG can safely charge the
battery. More power can be safely dissipated at ambient
temperatures below 70C. Less power can be safely dissi-
pated at ambient temperatures above 70C. The maximum
power dissipation for operation can be increased by 27 mW
for each degree below 70C, and it must be de-rated by 27
mW for each degree above 70C.
LAYOUT CONSIDERATION
The LP3945 and LP3946 have exposed die attach pad
located at the bottom center of the LLP package. It is im-
perative to create a thermal land on the PCB board when
designing a PCB layout for the LLP package. The thermal
land helps to conduct heat away from the die, and the land
should be the same dimension as the exposed pad on the
bottom of the LLP (1:1 ratio). In addition, thermal vias should
be added inside the thermal land to conduct more heat away
from the surface of the PCB to the ground plane. Typical
pitch and outer diameter for these thermal vias are 1.27 mm
and 0.33 mm respectively. Typical copper via barrel plating is
1 oz. although thicker copper may be used to improve ther-
mal performance. The LP3945 and LP3946 bottom pad is
connected to ground. Therefore, the thermal land and vias
on the PCB board need to be connected to ground.
For more information on board layout techniques, refer to
Application Note 1187 “Leadless Leadframe Package
(LLP)”. The application note also discuss package handling,
solder stencil, and assembly.
LP3945 AND LP3946 EVALUATION BOARDS
The LP3945 and LP3946 evaluation boards and instruction
manuals are available for order on National’s website
(www.national.com). The LP3945 evaluation board has on-
board I
2C interface capability for more flexibility. Please visit
National’s website for more detail.
20066518
w = write (sda = “0”)
r = read (sda = “1”)
ack = acknowledge (sda pulled down by either master or slave)
rs = repeated start
FIGURE 8. LP3945 (Slave) Register Read
LP3945/LP3946
www.national.com
14
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LP3946ILDX | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Battery Charge Management System |
| LP3946LD | 制造商:Rochester Electronics LLC 功能描述:STANDALONE CC/CV LIION BATTERY - Bulk |
| LP3946LD/NOPB | 功能描述:IC MANAGEMENT BATT CHARGE 14-LLP RoHS:是 类别:集成电路 (IC) >> PMIC - 电池管理 系列:- 标准包装:1 系列:- 功能:充电管理 电池化学:锂离子（Li-Ion）、锂聚合物（Li-Pol） 电源电压:3.75 V ~ 6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SC-74A，SOT-753 供应商设备封装:SOT-23-5 包装:剪切带 (CT) 产品目录页面:669 (CN2011-ZH PDF) 其它名称:MCP73831T-2ACI/OTCT |
| LP3947 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:USB/AC Adaptor, Single Cell Li-Ion Battery Charger IC |
| LP3947ISD-09 | 功能描述:电池管理 RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
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