Lpc2000

---- Original Message ----
From: "seangra" <sgraham@...>
To: <lpc2000@yahoogroups.com>
Sent: Thursday, November 10, 2005 9:11 PM
Subject: [lpc2000] Re: Is LPC2138 UART levels OK for a 5V part?

> Short answer, NO.
> 
> For any electrical part you can look in the schematics, find the "DC
> ELECTRICAL CHARACTERISTICS" section, and check the "INPUT HIGH
> VOLTAGE".  In your case it's minimum 3.4V, so the 3.3V output from
> the LPC2138 won't work.  Odd, because most 5V parts have an input
> high voltage around 2.5V, as it is with most of my parts on my
> design. 

That Vih,min of 3.4V is for the 1-wire pin.  I guess Johan wants to
connect the LPC2138 to the RXD and TXD pins which have Vih,min=2.7V,
and he should be okay without buffers.

Karl Olsen


> --- In lpc2000@yahoogroups.com, "fredrikssonjohan" <johan@s...>
> wrote: 
>> 
>> Sorry if this is a stupid question, but I haven't found any good
>> info about the UART levels so I better ask!
>> 
>> Need to connect a LPC2138 to a Maxim (Dallas) DS2480B which is on
>> 5V. Can they talk as it is or do I need a 3.3 to 5V buffer between?