----- Original Message ----- From: "Matt Pobursky" To: Sent: Thursday, January 08, 2004 9:08 PM Subject: Re: [PICLIST] [PIC:] RS232 Driver IC Supply Noise > Your problem appears to be source current/impedance related, since the > problem is getting better by adding bulk capacitance to the VCC of the > driver chip. You appear to be seeing noise/supply dips corresponding to > the switching of the charge pump in the driver chip. Adding more > capacitance to the PIC output will probably help. I just went for it and tried the 3.3 and 10uF caps (separately). The 20kHz noise, which does seem to be the switching current from the charge pump diminished greatly, but still when I sent character to the board from the PC, the Vcc on the driver chip dipped about 0.25V in the same pattern as before and the !INVALID output went low in the same pattern (about .2ms and then normal for about .1ms and then low again for about .1ms.). Given this, does this sound like it could be a failing driver IC? I am new to SMD soldering so I might have overheated the chip. I have a Chipquik kit so replacing it isn't any big deal but I wanted to exhaust other possibilities first as to me it doesn't seem likely to be the case. > I don't have the datasheet for the Maxim part handy... what is the > supply current specification for the part? 0.3mA typical, 1mA max. I actually have a TI branded part but it appears to be virtually identical to the Maxim (it even has the MAX part prefix). Nick -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics