Reset Supervisor

Development Boards MicroMod
1

Hi,

Does one need to use a reset supervisor like the one below http://www.st.com/stonline/books/ascii/docs/11110.htm for lpc2103 based design or the internal reset circuitry can take care in case of lpc2103.

bye

Mohit

2

Here are some questions on the same page:

  • Do we need a supervisor on core votage also (outputs of the core and peripheral supervisors ORed)?

  • Are there good application notes on reset supervisors for ARMs?

3

I don’t know about 2103, but I have a 2138 board and a 2148 board with only an 100N cap from the reset pin to ground, and a 10K resistor from the reset pin to +3.3V. Have had no reset problems whatsoever.

I will speculate that a reset IC might be helpful if you plan to use a JTAG programmer which might add some loading to, or otherwise influence the reset circuit. A reset IC provides a very hard ground at startup and a pretty sharp edge when it lets go, whereas a simple RC network depends on some hysteresis on the reset input, which NXP says is built in on the pin. You can certainly have pads on your circuit card for both options, but only populate the reset IC for development.

4

I’ve looked at this Olimex board http://www.olimex.com/dev/pdf/LPC2103.pdf. It has a MCP130T supervisor. However, I would connect the manual reset button to the supply of MCP130T instead of the /RST. /RST node shouldn’t see switch bounces.

5

Here’s a NXP application note that shows a 2101 used with just a capacitor and resistor on the reset pin. I think the Olimex boards use the MCP130 mostly because that’s how they’ve always done it, and they’ve got a bazillion of 'em on the shelf.

http://www.nxp.com/acrobat_download/app … 0513_1.pdf