Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

ADC noise goes away when UART connected

Status
Not open for further replies.

RogerFL

Newbie level 2
Joined
Apr 4, 2012
Messages
2
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,283
Activity points
1,291
I have a Kinetis MCU design that senses temperature from a PTD using the internal 16-bit ADC. It also has a UART that I use as a console port for development. When the UART is plugged in (to a FTDI cable), the ADC input is very stable with all samples within a 3 unit range. When I unplug the UART, the samples are much noisier with a range of about 30 units.

Any ideas on what would cause this?
 

Lack of CMMR on unbalanced lines causes differential noise. UART has ground which lowers CM impedance to suppress stray cap. Coupled RF or E fields at line f. Thus you need a large ferrite CM choke and small RF filter cap (NP0) to common across inputs.

- - - Updated - - -

Lack of CMMR on unbalanced lines causes differential noise. UART has ground which lowers CM impedance to suppress stray cap. Coupled RF or E fields at line f. Thus you need a large ferrite CM choke and small RF filter cap (NP0) to common across inputs.

Added..
NP zero or oh as often said are not only zero tempco. But lower k dielectric and lower ESR at RF f.
 
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top