spartan-3A FPGA入门套件输出引脚输出电流是否可以在400到3毫秒左右

单个引脚上的400mA电流很可能会很好地炸掉你的FPGA :-)通常，数字输出仅限于几mA，通常介于3到30mA之间。你想用这种电流驱动什么？
您可能需要查看分立MOSFET或达林顿驱动器（例如ULN2003可以驱动500mA）。
它们可以从FPGA的数字输出驱动。注意，Wolfgang



以下为原文

400mA on a single pin will most probably fry your FPGA for good :-)
Normally digital outputs are limited to just a few mA, somewhere between 3 and 30mA typically.

What do you want to drive with that kind of current? You may want to have a look at discrete MOSFETs, or Darlington drivers (ULN2003 for example can drive 500mA). They can be driven from your FPGA's digital output.

Regards,

Wolfgang

嘿，
thx回复沃尔夫冈。
我想用脉冲400mA电流驱动SMA材料3秒，每5分钟一次。
我有6个这个SMA来激活。
我将在FPGA中对定时器进行编程，但我认为我也可以从套件中获得400mA的电流。
（这不是我的想法，为此我使用fpga，我仍然认为这不是一个好选择，但客户想要使用它）
对此有什么简单的想法？
谢谢



以下为原文

hey, thx for the reply Wolfgang. i want to actuate a SMA material with a pulse of 400mA current for 3 sec, every 5 min. i have 6 of this SMA to activate. i will programme the timer in the FPGA, but i thought i could have a 400mA current from the kit too. (it was not my idea to use the fpga for this, i still think is not a good option, but the client wants to use it) any simple ideas for this? thanks

首先，什么是SMA ???
（对我来说，它是一个同轴射频连接器...可能不是你的意思）如果我理解正确你想要做两件事：（1）打开和关闭相当大的电流，由FPGA的数字输出控制。
（2）无论电源电压或负载阻抗如何，都要调节电流，使其恒定为400 mA。我没有看到直接从数字输出端执行此操作的好方法。
即使您设法将其中许多并联，并假设总电流不会扼杀您的FPGA，仍然没有任何电流限制（或调节）。
您真的需要在FPGA之外添加可切换的恒定电流源。使用单个元件同时执行这两个操作非常简单的方法是使用具有可调输出电压和关断输入的低压差稳压器
。
将检测引脚与一个与SMA串联的小电阻（可能是1欧姆）组合使用，以检测电流。
您必须添加一个运算放大器，该放大器从检测电阻获取检测电压，并提供增益和偏移，以满足稳压器检测输入的电压范围要求。
此外，低通滤波和积分器阶段是必要的，以使其成为真正的伺服环路并防止振荡。使用连接到FPGA的关闭输入来打开和关闭电流。我同意，FPGA不是
这个应用程序的非常好的选择，除非有其他功能需要它。
鉴于速度要求慢，我会使用一个简单的微控制器甚至是基于555的定时器电路。顺便说一下，我有时会在侧面进行一些定制电路开发以获得乐趣，所以如果你想让我设计和构建所描述的
电路给你，让我知道（你可以直接给我发电子邮件gwen.and.wolfgang [at] ***cglobal.net）WolfgangMessage由womai编辑于11-14-2007 12:14 PM



以下为原文

First, what is an SMA???  (for me, it is a coaxial RF connector... probably not what you mean)

If I understand correctly you want to do two things:

(1) switch a sizable current on and off, controlled by a digital output from your FPGA.

(2) regulate that current so it is a constant 400 mA no matter what the supply voltage or the impedance of your load is.


I don't see a good way of doing this directly from your digital outputs. Even if you manage to parallel many of them and assuming that the total current does not kill your FPGA, there is still no current limiting (or regulation) whatsoever. You really need to add a switchable constant current source outside of and driven by your FPGA.


A very simple way doing both at the same time with a single component is to use a low-dropout voltage regulator that has adjustable output voltage and a shutdown input. Use the sense pin in combination with a small (maybe 1 Ohm) resistor in series with your SMA to sense current. You will have to add an op-amp that takes the sense voltage from your sense resistor and provides gain and offset to match the voltage range requirements of the regulator's sense input. In addition, low-pass filtering and and  integrator stage is necessary to make it a true servo loop and prevent oscillations.

Use the shutdown input connected to your FPGA to turn the current on and off.


I'd agree, an FPGA is not a very good choice for that application unless there is other functionality that requires it. Given the slow speed requirement, I'd use a simple microcontroller or even a 555 based timer circuit instead.

By the way, I sometimes do a little custom circuit development on the side for fun so if you want me to design and build the decribed circuit for you, let me know (you can email me directly at gwen.and.wolfgang[at]***cglobal.net)

Wolfgang



Message Edited by womai on 11-14-2007 12:14 PM