You can easily add margining capability—that is, the ability to digitally adjust the output voltage—to a dc/dc converter by making a single connection to the circuit (Figure 1).

The dashed line in the figure shows the connection. The extra IC is a two- or four-channel, I2C (inter-integrated-circuit)-adjustable-current DS4402 or DS4404 DAC. Because each DAC output is 0 mA at power-up, the extra circuitry is essentially transparent to the system until you write a command using the I2C bus.

For example, assume that the input voltage is 3 to 5.5V; the output voltage is 1.8V, which is the desired nominal output voltage; and the feedback voltage is 0.6V. You can obtain the feedback voltage from the dc/dc converter’s data sheet; be sure to verify that it is within the output-voltage range that the current DAC’s data sheet specifies as sinking or sourcing voltage depending on whether you are sinking or sourcing current. You should also verify the input impedance of the dc/dc converter’s feedback pin. The circuit in Figure 1 assumes a high impedance.

Assume that you want to add a ±20% margining capability to the dc/dc converter’s output so that the maximum, nominal, and minimum output voltages would be 2.16, 1.8, and 1.44V, respectively. First, determine the necessary relationship between R1 and R2, which yields the nominal output when the current of the DS4404 DAC is 0 mA:

where the margin is 0.2 to implement ±20% margining in this case. Before you can use this relationship to calculate R1 and R2, you must select the full-scale current.

According to the DS4404’s data sheet, the full-scale current must be 0.5 to 2 mA to guarantee the specifications for accuracy and linearity. Unfortunately, no formula is available for calculating the ideal full-scale current. The desired number of steps, the step size, and the values for R1 and R2 influence that value. Another factor affecting the full-scale current value is whether there is a requirement that a particular register setting corresponds to a particular margin percentage.

In any case, your selection of a full-scale current will likely require several iterations, in which you select an arbitrary value within the range and then calculate R1, R2, RFS (full-scale resistance), and step size. When you’ve determined an acceptable full-scale-current value, you may want to further adjust it or some of the resistor values to ensure that the resistor values you finally specify are commonly available.

To calculate R1 for the original example, make the full-scale current equal to the current of the DS4404. This step gives you 31 equal increments, or steps, from the nominal output voltage to the maximum output voltage, as well as 31 steps from the nominal output voltage to the minimum output voltage. This resolution is more than adequate for this example.

You could, for instance, begin by arbitrarily choosing the full-scale current in the center, or 1.25 mA, of the specified range and then performing all the calculations. Instead, for illustrative purposes, the calculations are shown for the endpoints of the range: 0.5 and 2 mA. Analyzing the 0.5-mA case first, you perform the following calculations and then repeat for the 2-mA case.

Using Equation 9 and solving for R1 yields:

Note that this register setting does not include the sign bit, which selects sink or source. The DS4404 sinks current when the sign bit is zero, making the output voltage increase to the maximum output voltage. It sources current when the sign bit is one, making the output voltage decrease toward the minimum output voltage.

Now, you can repeat the calculations for the 2-mA case.

Add margining capability to a dc/dc converter的更多相关文章

  1. PID DC/DC Converter Controller Using a PICmicro Microcontroller

    http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en011794 ...

  2. Simple dc/dc converter increases available power in dual-voltage system

    The schematic in Figure 1 shows a way to increase the power available from a current-limited 5V supp ...

  3. LT1946A-- Transformerless dc/dc converter produces bipolar outputs

    Dual-polarity supply provides ±12V from one IC VC (Pin 1): Error Amplifier Output Pin. Tie external ...

  4. Practice safe dc/dc converter

    Short-circuit protection is an obvious requirement for a power supply, especially when its load conn ...

  5. [专业名词·硬件] 2、DC\DC、LDO电源稳压基本常识(包含基本原理、高效率模块设计、常见问题、基于nRF51822电源管理模块分析等)·长文

    综述先看这里 第一节的1.1简单介绍了DC/DC是什么: 第二节是关于DC/DC的常见的疑问答疑,非常实用: 第三节是针对nRF51822这款芯片电源管理部分的DC/DC.LDO.1.8的详细分析,对 ...

  6. DC/DC与LDO的差别

    转自:http://bbs.eetop.cn/thread-459121-1-1.html 在平时的学习中,我们都有接触LDO和DC/DC这一类的电源产品,但作为学生的我们队这些东西可能了解不够深刻, ...

  7. DC DC降壓變換器ic 工作原理

    目前DC/DC轉化器大致可分為:升壓型dc dc變化器.降壓型dc dc變化器及可升壓又可降壓dc dc變換器.我們今天主要提一下降壓型dc dc變換器的原理: 見下圖降壓變換器原理圖如圖1所示, 當 ...

  8. DC DC電路電感的選擇

    注:只有充分理解電感在DC/DC電路中發揮的作用,才能更優的設計DC/DC電路.本文還包括對同步DC/DC及異步DC/DC概念的解釋.   DCDC電路電感的選擇 簡介 在開關電源的設計中電感的設計為 ...

  9. (笔记)电路设计(十一)之DC/DC电源转换方案设计应用

    十大 法则之一:搞懂什么是DC/DC电源以及DC/DC转换电路分类 DC/DC电源电路又称为DC/DC转换电路,其主要功能就是进行输入输出电压转换.一般我们把输入电源电压在72V以内的电压变换过程称为 ...

随机推荐

  1. Docker Commands

    Docker Commands 安装,以Ubuntu 14.04.3为例 apt-get install docker.io 注意安装之前需要更新系统 列出曾经存在的容器 docker ps -a 列 ...

  2. angular项目中使用jQWidgets

    Angular CLI with jQWidgets In this tutorial, we will show you how to use https://cli.angular.io/ alo ...

  3. java并发容器

    同步容器将所有对容器状态的访问都串行化,以实现线程安全性.这种方式的缺点是严重降低并发性.Java 5.0提供了多种并发容器来改进同步容器的性能.如ConcurrentHashMap代替同步且基于散列 ...

  4. 关于IdByName 为什么一个消息主题要有 Id和 Name的解释

  5. LeetCode862. Shortest Subarray with Sum at Least K

    Return the length of the shortest, non-empty, contiguous subarray of A with sum at least K. If there ...

  6. csu 1769(数学)

    1769: 想打架吗?算我一个!所有人,都过来!(3) Time Limit: 2 Sec  Memory Limit: 128 MBSubmit: 262  Solved: 76[Submit][S ...

  7. 如何修改WP文章字体格式、字号大小、字体颜色

    在使用wordpress编辑文章的时候,很多朋友会像小编一样,发现它并没有像word文档一样有修改字体样式.字体大小.字体颜色.分页符等功能按钮,对我们写文章极为不便,原因是wordpress默认使用 ...

  8. ADO.NET怎删改+vs 2013 C#

    一.删除 string constr = "server=.;database=test;uid=sa;pwd=sa";            SqlConnection myco ...

  9. jupyter notebook :一个交互式计算和开发环境

    一. IPython基础 代码自动补全:Tab键 可补全内容包括:变量名.函数名.成员变量函数.目录文件 内省(Itrospection) 在变量名之前或之后加上问号(?),这样可以显示这个对象的相关 ...

  10. 【JAVAWEB学习笔记】11_XML

    今日内容介绍 编写服务器软件,访问指定配置内容 访问tomcat下已经发布的web项目 今日内容学习目标 可以编写xml存放任意内容 通过DTD约束编写指定格式的XML 通过Schema约束编写指定格 ...