The quick guide to layout cons

2011-10-25 18:09:32来源: 互联网 关键字:layout
IntroductionMaxim describes a lithium-ion (Li+) battery simulator circuit in application note 4322, "Simplified lithium-ion (Li+) battery-charger testing." While Maxim does not sell evaluation (EV) boards for this circuit, the Company has received multiple requests for one. Responding to customer interest, this application note provides some basic layout guidelines and considerations for designing your own board.

Test board for the battery simulator

Making a board for the Li+ battery simulator does not need to be complicated or expensive. Most of the layout can be done with a simple two-layer breakout board, however, some consideration does need to be paid to power connections and heatsinking requirements.

As seen in Figure 1, the major power path of the simulator circuit begins at the BATT+ node, flows through the 100mΩ series input resistance and the TIP35 transistor, and returns at the BATT- node.


Figure 1. "Charge" current path in the Li+ battery-charger simulator.

Assuming a 3A charge current, the input sense resistor must handle at least 900mW. To ensure a constant input series resistance during operation, use a resistor capable of handling more than 1W. A single 5W resistor or multiple 1W resistors in parallel work well.

The TIP35 transistor handles the bulk of the power through the circuit in both point-by-point mode and integrating mode. Under the worst-case conditions, power across the TIP35 transistor can be calculated as:
PTIP35 = (VBATT+ - VBATT-) × IBATT
PTIP35 = (4.2V) × 3A = 12.6W
For a safety margin, use a heatsink capable of handling 15W or more. In testing the circuit, we used a thick 0.1cm x 10cm x 18.5cm piece of copper to heatsink the TIP35. Connect the TIP35 to the board using thick traces (or wires) to reduce voltage drop and ensure accuracy.

Figures 2 and 3 show a sample layout for a 2-layer board. Figure 2 also shows the component labels for the layout in Figures 3A, 3B, and 3C. The board is set up to use multiple sense resistors (up to five) in parallel for the input series resistance; it also allows a second capacitor across the NDS0605 MOSFET. (We used two 0.047µF capacitors here). Although not shown in the figures, use vias between BATT- and the bottom layer for better ground connections. Figure 3 shows the component placement on both layers of the board.


Figure 2. Li+ Battery simulator layout for a 2-layer board.


Figure 3. Component placement on the board. Component reference numbers in Figures 3A, 3B, and 3C are shown in the layout of Figure 2. Figure 3A. Li+ battery simulator circuit, 2-layer board, component placement. Figure 3B. Li+ battery simulator circuit, 2-layer board, top layer. Figure 3C. Li+ battery simulator circuit, 2-layer board, bottom layer. 

The TIP35 transistor is connected to the circuit at the edge of the board and is connected externally to a large copper heatsink (Figure 4). Thermal paste has been used to enhance the connection between the transistor and the heatsink.


More detailed image (PDF, 916kB)
Figure 4. Li+ battery simulator with external heatsink.

关键字:layout

编辑:神话 引用地址:http://www.eeworld.com.cn/mndz/2011/1025/article_12524.html
本网站转载的所有的文章、图片、音频视频文件等资料的版权归版权所有人所有,本站采用的非本站原创文章及图片等内容无法一一联系确认版权者。如果本网所选内容的文章作者及编辑认为其作品不宜公开自由传播,或不应无偿使用,请及时通过电子邮件或电话通知我们,以迅速采取适当措施,避免给双方造成不必要的经济损失。

上一篇:基站建设中共站型电源解决方案
下一篇:基于LTC3675设计的七路大功率PMIC管理技术

关注eeworld公众号 快捷获取更多信息
关注eeworld公众号
快捷获取更多信息
关注eeworld服务号 享受更多官方福利
关注eeworld服务号
享受更多官方福利
推荐阅读
全部
layout

小广播

独家专题更多

东芝在线展会——芯科技智社会创未来
东芝在线展会——芯科技智社会创未来
2017东芝PCIM在线展会
2017东芝PCIM在线展会
TI车载信息娱乐系统的音视频解决方案
TI车载信息娱乐系统的音视频解决方案
汇总了TI汽车信息娱乐系统方案、优质音频解决方案、汽车娱乐系统和仪表盘参考设计相关的文档、视频等资源
电子工程世界版权所有 京ICP证060456号 京ICP备10001474号 电信业务审批[2006]字第258号函 京公海网安备110108001534 Copyright © 2005-2017 EEWORLD.com.cn, Inc. All rights reserved