AD7195: Input impedance in buffered mode

Question I am using the AD7195 in buffered mode. I need to know the input impedance between the AIN+ AIN- inputs. In the data sheet is only written that is high. But which is (more or less) its value ? Answer With the buffer of the AD7195 (http://www.analog.com/AD7195) enabled, the input current is 2 nA maximum for a gain of 1 and 4.5 nA maximum for higher gains. Kindly find these values in table 1 on page 4 of the specification. For your reference I’ve copied the relevant section below. So, if the input voltage is 5V, then the impedance is: 5V/4.5nA = 1Gohm. Kindly mark, that this is a worst case scenario of the AD7195.

Pros and cons of applying SYNC pulse on AD7195

Question Using the AD7195 sync. signal. AD7195 is running 400Hz continues mode. I receive a new sample each 2.5 msec. But after a sync signal pulse (100uSec) it takes ~10msec before the next sample is ready ? I was still expecting ~2.5msec ?! Answer When the SYNC signal is applied, the modulator and filter are held in the reset state. When \SYNC goes high, the modulator and filter are released from the reset state and they begin to gather samples. The complete settling time is allowed for the device to generate the first conversion so with the sinc4 filter, chop off, the time is 4/output data rate or 10 ms for your case. Applying the SYNC pulse causes the same behavior as a channel change. However, the benefit of the SYNC signal is that you can control the instant at which conversions are available.

Mosfets for AD7195 AC excitation

Question In our new design for weighing scales we have used the AD7195. For AC excitation BSH201 and BSH112 mosfets are used in the reference design. But we need to connect up to 10 load cells, so we would prefer using mosfets with much lower on resistance (factor 10) to minimize the voltage drop. 1) We have looked at some complementary types like IR7309 and SI5513CDC. Are they ok for the job? 2) Could Analog Devices recommend some mosfet types which adds minimum noise to the supply lines and the solution? Answer The AD7195 evaluation board uses the mosfets that we recommend. We have not tried other mosfets. However, the mosfets you mentioned should be ok. Using the mosfets on the evaluation board, we have evaluated the noise performance and the mosfets do not degrade the noise performance.

English

Forums
Popular Forums
Product Forums
View All
Application Forums
Design Center Forums
Learn
Highlighted Webinar

Fast-Track Certification: Leveraging IC Safety App Notes for Functional Safety Designs
Stop guessing, start certifying. Learn how to use IC safety application notes to streamline your FMEDA and meet IEC 61508 and ISO 13849 standards with...
Places
Libraries
Upcoming Learning & Events
- 3 Real World Methods to Make Your Power Supply More Intelligent
View All Webinars
Community Hub
Challenge Yourself!
View All
What's Brewing
View All
Places
Resources
View All
ContentZone
Visit ContentZone
Search content by industry or technology.

Blogs

Technical Articles

Tutorials

Videos

Webinars

Your ADI content all in one place.
View ContentZone
The Latest Read

Master FPGA-Based DSP Design: The Complete Building Blocks Guide You Need to Read
The Engineering Mind Blog on EngineerZone presents an exceptional five-part series titled " DSP Building Blocks " that walks engineers through the essential...

New Release

Signal Chain Designer: DC Error Simulation
This video covers the DC error calculation capabilities of Signal Chain Designer. DC error is unique in that often requires calibration and has so many...

Recent Technical Insights

PSM Integration for Enhanced Module Solutions in 48 V Data Centers
The integration of the LTC2971 into quarter brick solutions for 48 V data centers enhances monitoring, control, and reliability by providing high precision...

EngineerZone

Precision ADCs

Log In

User
Site
Search

OR

Ask a Question

Data Converters

Precision ADCs

Documents AD7195: FAQ

Q&A
File Uploads
FAQs/Docs
Help Articles
Members
Tags
Cancel

Products Mentioned

AD7195 Recommended for New Designs
The AD7195 is a low noise, complete analog front end for high precision measurement applications. It contains a low noise, 24-bit sigma-delta (Î£-Î”) analog...
Datasheet
AD7195 on Analog.com