Questions tagged [mixed-signal]

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12
votes
1answer
2k views

PCB microcontroller layout in a mixed-signal system

This is a direct continuation of this question. So here's my layout, what do you think about the microcontroller side? UPDATE April 2019: I built the board in spring/summer 2016, but never got around ...
11
votes
1answer
528 views

Design essentials when working with 12bit ADCs

I'm currently designing a board that is attaching a 12bit ADC (MCP3208) to a Raspberry Pi (besides a few other low speed I/O related stuff). It will mostly be attached to analog sensors (temp sensors, ...
11
votes
3answers
3k views

Details on PCB layout for microcontroller

Update: the follow-up question shows my take on the resulting PCB layout. I'm laying out my first board with a uC (I've got a reasonable amount of experience in using and programming embedded systems,...
8
votes
1answer
2k views

Proper way of connecting logic GND / power GND on MOSFET driver

I am tring to build half bridge using IR21844 mosfet driver, i have read datasheet and design tips and some of the topics in this forum. The one thing i still cannot get is the separate GND pins ...
7
votes
2answers
183 views

What's the best ground topology for this mixed signal board?

I'm designing a 4 layer mixed signal PCB with sensitive analog circuits and RF-digital circuits. The board have many mechanical constraints so the places of the analog and digital circuits are fixed. ...
6
votes
1answer
269 views

Review of my first ever PCB design for a watering control robot.

I'm building a small watering control for one of my large indoor plants. This is my first real electronics project outside of school. Although I studied EE at university and did my basic component and ...
5
votes
1answer
2k views

How does a Delta-Sigma DAC work?

I have looked at how the Sigma-Delta ADC works and I understand it. However, it seems to me that there is not a lot of literature about the Sigma-Delta DAC. I want to build a model of it in Simulink....
5
votes
1answer
240 views

Help to translate jitter design constraint in a frequency synthesizer design with 4046 and 4017 ICs

I'm trying to design a frequency synthesizer with the old-school 4046 and 4017 ICs, with a scaling factor N = 1,5,7,10. The input signal is a square wave with adjustable frequency from 1 kHz to 10 ...
5
votes
0answers
186 views

Help with deciding my layout for EMC tests and SI. Different alternatives

I am thinking of what way would be the best to layout my system in order for it to have the best SI and pass EMC tests. My system consists of two PCBs joint by a flat flex cable (up to 7cm) and these ...
4
votes
1answer
2k views

Back to back Schottky diodes between ground connections

In a mixed-signal IC, you most likely will have two ground planes, analog ground and digital ground. This seems fair enough and easily understandable but my real question is: Why would you need to ...
3
votes
3answers
276 views

How Can the Quantization Noise of an ADC be Measured using the Digital Output?

The ADC quantization noise is the error signal generated by rounding the sampled analog values of signal. Suppose that we have the digital output of an ADC, how can we measure the quantization noise, ...
3
votes
5answers
324 views

Decoupling capacitors values in mixed-signal circuit

I know theory about decoupling capacitors (ESR, ESl, parallel capcitors etc.) I have read Electromagnetic Compatibility Engineering, H.W. Ott. My question is about practical design. How shall i ...
2
votes
3answers
3k views

DIY mixer - use diodes to prevent input potentiometers influencing each other

I've builded a simple amplifier (just stereo audio in, two speaker outs) and I'm building a mixer for it. There are some audio inputs, which goes through stereo potentiometers (volume for each input)...
2
votes
2answers
270 views

The right way to mix digital signals

I have a dozen of sources of digital signal, 16-bit signed words. I have implemented very simple mixer where all sample values are summed, and then shifted right to prevent overload. Unfortunately ...
2
votes
2answers
222 views

Where should a switching regulator be placed in relation to analog and digital circuitry?

General Layout: I've partitioned a mixed-signal board as follows: The dashed blue line indicates the analog/digital divide, but it is NOT a ground cut. This layout is intended to avoid analog and ...
2
votes
1answer
365 views

PCB plane cuts for audio paths in mixed-signal device

I am working with the TLV320AIC3204 32-bit audio codec. The codec has three inputs and two outputs. While I was designing my own test PCB, I noticed on TI's evaluation board (on page 33) that they ...
2
votes
2answers
50 views

MOSFET Capacitance clarification

2 part question here. Are there ways to directly test the input and output capacitance of a MOSFET, Ciss and Coss? On that note, due to internal inductance and capacitance, is it possible for a ...
2
votes
1answer
82 views

Understanding mixed-signal PCBs, in most simple sense

I understand that mixed-signal is a circuit that obviously has both analog and digital circuits. I am trying to understand what really would be classified as mixed-signal. If you had a PCB with some ...
2
votes
1answer
387 views

Mixing two square waves and isolating intermodulation component

I currently have two square wave signals at f1 and f2 (f1 >> f2) that serve as reference signals to two separate lock-in amplifiers that are subsequently connected in cascade to extract the component ...
2
votes
2answers
3k views

PCB ground plane separation between power and analog sections of board

In this design I have separated the ground plane of the sensing/controlling circuit from the high-power 3-4 amp circuit. This is a current controller. The ground planes are joined at the sensing ...
2
votes
0answers
62 views

Reducing the offset voltage of a source follower

I am currently trying to reduce the offset voltage of the circuit attached below to less than +/- 2mV over a 1V to 4V input range. I have a few constraints for this task: I can use ...
1
vote
2answers
204 views

What is the role of discrete resistors and capacitors in a motherboard? [closed]

I know the basic function of resistors and capacitors. I know filters, oscillators, one-shot, differentiator/integrator, ADC/DAC, power supplies, etc. But in a motherboard why are there so many ...
1
vote
2answers
125 views

Ways to multiplex the output of a DAC?

Part searching in microcontrollers, it looks like most small ones have at most one DAC. What is the just way or ways to output multiple slow signals from a microcontroller with at most a single DAC? ...
1
vote
3answers
357 views

Where do I put digital ground in a dual-rail mixed signal circuit?

I'm working on a project for school (a discrete dual-slope ADC) that will combine digital and analog circuitry and operate off of a ±15V dual-rail supply. The "analog ground" will be at 0V, as ...
1
vote
1answer
235 views

Mixed Signal Grounding: Which approach will yield better isolation and analog performance?

I'm laying out a mixed signal PCB and I'm trying to decide between (1) separating the ground planes for the digital and analog/digital circuits completely [shown in top figure] or (2) keeping the two ...
1
vote
1answer
105 views

5VDC and 10VAC on the same PCB - what happens on 10V goes to 5V ground?

Me and a colleague (we are both EE-trainees) had a chat the other day about mixed voltages on the same PCB. She pointed out an interesting question that I was not able to solve. Imaging having a PCB ...
1
vote
1answer
372 views

How to create a mixed signal pcb

I want to create a board that has both high speed digital components (specifically the SAM3X8E - from arduino DUE) and an analog audio circuit. The analog parts were originally a shield to the ...
1
vote
3answers
329 views

How to live with noise and ground loops in a system with Electronics, Power Electronics, Electrical Machines, Three-phase power and several boards?

I ask for help with a experimental assembly I am developing in the university, which is a small size power generation plant. The system consists of a DC machine, a induction machine, several current ...
1
vote
0answers
59 views

Pull-ups in a mixed voltage environment

I'm working on a circuit where a 12 VDC line is switched from a USB-powered microcontroller (U1, running at 3.3 V, specs below). I want to ensure that the switch ...
1
vote
1answer
70 views

Where to place RF shield

I'd like to put a pump drive circuit similar to the one shown below on the same PCB that has two I2C devices, a GPS module, seven analog signals, an ESP32 MCU transmitting WiFi via a trace antenna, ...
0
votes
2answers
57 views

Signal fidelity from fiber optic crosstalk

I was watching a video about tapping fiber optic cables when it brought up some points from an early US govt document describing security concerns about fiber optic cables. The relevant part: ...
0
votes
1answer
60 views

Can you make an electric gamma ray emmiter by adding up frequencies with freq. mixers up until you reach gamma ray herz quantities?

I just thought this up. Theoretically if you can add freq numbers you can get to large quantities like in a calculator, only this time mixing electric frequencies using amounts of circuitry right? Is ...
0
votes
2answers
402 views

VHDL-AMS simple code but std_logic_vector to quantity issue

I am working on a Mixed signal model where the symbol looks like the following, The signal to the left is count_val which is std_logic_vector(7 downto 0) and p,m are the terminals which have ...
0
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2answers
30 views

“analog” /“mixed-signal” Terminology confusion about the definition of some components and systems

I sometimes encounter that ADCs, DACs, PLLs, DC-DC converters and oscillators are called mixed-signal but sometimes they are grouped under the category of analog. Is there a consensus about that?
0
votes
1answer
49 views

Mixed digital/analog rails and level-shifting components best practices

I am designing a board with a ±2.5V analog domain and a 3.3V digital domain where space is at a premium. Digital and analog grounds only connect at a single point near the supplies. As such I am using/...
0
votes
3answers
658 views

Superimpose a High Frequency AC Small Signal on a DC Power Signal

I am facing a challenging problem with a circuit that I am currently working on, I would like others input and thoughts. I have a DC power signal that I am injecting a AC small signal this mixed ...
0
votes
1answer
208 views

LOW and HIGH definition for Enable pin of 4051?

Suppose we have connected an X volt (X=10) as the supply of a 4051 MUX (which is active LOW), can we disable the device by applying a B volte (assume B is 5 volt). In other words, how high is HIGH ...
0
votes
1answer
184 views

Does placing digital circuitry between the regulators and analog circuitry cause grounding problems?

I'm designing a mixed-signal PCB and have been using this Maxim guide to help me with layout. The guide has instructed me to avoid making cuts to the PCB and instead think about ground return paths. ...
0
votes
1answer
189 views

What is the best method to determine bypass capacitors for each chip in Mixed-Signal Systems? [closed]

In datasheets of chips, usually they have reference designs and to those designs bypass capacitors are predetermined. But, when I examine some high level designs of those chips I see different bypass ...
0
votes
1answer
221 views

Separating ground planes with different potentials?

Im currently building a signal generator and have a problem with placing multiple different ground planes which have different voltages. The system is powered off of USB, so all my digital logic ...
0
votes
1answer
586 views

Input/output for buck-boost converter controller implemented with FPGA

I am trying to implement a voltage controller for a buck-boost converter using FPGA. The control method I'm trying to use is in this paper: www.engr.iupui.edu/~aizadian/index_files/Papers/C-28.pdf ...
0
votes
0answers
22 views

Mixing Symfonisk high/low-mid output channels

So i've been messing with this issue for a couple of months and it's just that my electronics knowledge isn't reaching far enough. I have a Symfonisk speaker by Ikea, which outputs a low and high/mid ...
0
votes
1answer
43 views

A novice question about mixed signal IC design

As far as understand, a digital IC like a DSP can be design by RTL methods and by using languages like Verilog and VHDL. And if I'm not wrong, we cannot yet program pure analog chips by using a ...
0
votes
1answer
35 views

Multiple PCB system vs mixed-signal PCB

I'm designing a high-frequency (\$6\,\text{GHz}\$) mixed-signal PCB. The design contains some noise-sensitive RF analog circuitry (mixer, LNA, 12-bit ADC, etc.) as well as some noisy digital circuitry ...
0
votes
1answer
136 views

Parasitic insensitive switched capacitor circuit

I'm trying to simulate the parasitic insensitive switched capacitor circuit shown here: I am using cadence virtuoso. My input is a sine wave of 1 V amplitude, 0 DC and 1 kHz frequency. I am using ...
0
votes
0answers
27 views

mismatch in register delays between lib files and generated sdf file (Synopsis Design Compiler)

The recovery time in sdf file of register is unrealistic delay as it is 50ns and this not the only problem, but the same register in anther place in the design has recovery time 0.3ns ! and recovery ...
0
votes
1answer
163 views

Crossing ground planes with low current low frequency signals

I have a board which has two ground planes, analog and digital, that on this board are completely separate. The grounds connect on another board, which is connected via a flat cable. All signals on ...
0
votes
2answers
67 views

Connecting mixed-speed multiple serial devices to two microcontrollers

I'm trying to figure out the best way to integrate all devices flawlessly on the 8051 based microcontrollers. If each device was the same low speed, then I could multiplex each and every one of them ...
0
votes
0answers
46 views

lm13700 as Diode laser voltage to current converter

I generated two Signals, one using dac7611 (ramped signal with fre = 0.04hz ) and the other one, using AD9833 DDS (sin wave with fre = 32 KHz) then generated signals added using ad620an. Is this ...
0
votes
1answer
42 views

Mixed-Signal modular system grounding scheme

I'm attempting to create a sensitive, precise mixed signal system (more than 24bit) compose of a backplane and stacked modules on 2.54mm headers.It is multi-channel and channel's modules are well ...