Hi All ,
I have an requirement to convert the 8 channel analog input (Single ended - bipolar) signal with the range of 10Vpp, The waveform will be sin, ramp, square,and Sweep.
Hence I am planing to use AD7768. In this I need a clarification of following points:
1. I have 8 channel single ended bipolar signal inputs (10Vpp, +/- 5 ), So I will connect this signal to the correspoding port of (AIN0+ to AIN7). My question is, May I Ground it the remaining ports of AIN-0 to Ain7- ?
2. My input signal should support (+5V to -5V , 10Vpp), so in REF1- and REF2- may I connect to Ground or -2.5V should give ?
3. If I ground the REF1- and REF2- , The AD7786 support the input signal swing 10Vpp?
4. Even though My Signal is single ended bipolar , Is there I want to make this signal to converted into differential bipolar (True Biploar signal)?
Please clarify the points as soon we are going to finalise the design stage.
Thanks for your inputs,
As we are using 8 Channel Inputs, Each channel inputs I should convert single end to differential end bipolar signal using LTC6363.
With your design reference discrete components occupy more spaces.
My board dimension will be 4.5 cm circular dia.
I have another query,
1 ) If I will attenuate the signal range from 10Vpp to 5Vpp (That is AIN input signal range +2.5 to -2.5V) signal range.
How i should connect the power inputs (AVDDx , AVSSx) and reference inputs (REF+x and REF-x)?
2) If I give differential Input signal (-2V at AIN1+ ; +2V to AIN1- ) what will be the output data? can you give me the conversion formula ? what REF+x and REF-x I should give ?
Thanks and Regards,
Thank you very much for your inputs !!!
I am going with AVDDx, REF+x = +2.5V using ADP7118 ; and AVSSx , REF-x = -2.5V using ADP7183ACPZN2.5-R7
Is this LDO Current is enough for AD7768 Supply ?
I have an rearranged architecture of my 8 Channel Receiver card.
Before the architecture is :
Re-arranged architecture :
Can you give me your clarification of following parts.
Is this right way of attenuate my signal range ? or do you have any recommended part for this design?
This single ended to differential end conversion is there right part to do the conversion instead of you recommended LTC6363.
Please confirm may I go ahead with this part ?
I just stumbled across this post, and wanted make some comments on the signal chain you have posted on August 21.
You show the ADA4922-1 driving the AD7768 - The ADA4922 will cause performance degradation of the AD7768 at the maximum sample rate. As the AD7768 samples the output of the ADA4922, it injects a small amount of charge onto that node at the beginning of each acquisition. The amplifier that drives that node needs to be able to recover from that disruption quickly, and drive that node back to the proper voltage.
Niall is recommending the LTC6363 or the ADA4940 b/c they are capable of driving the AD7768 at it's full sample rate.
The ADA4922 *might* be able to drive the AD7768 when using a much lower fmod than the maximum value. Here's a snippet regarding fmod from the datasheet:
One of the specs that's critical in this application is GBWP:
Faster is not necessarily better, but for this ADC, 40MHz GBWP is probably too low for the driver to fully settle between samples.
On the other hand, if you're willing to use a lower fmod, the ADA4922 might work fine.
Greeting for the day !!!
I made a mistake in the block-diagram , In that my input is differential 10 Vpp signal which is fed to the PGA AD8253 .
The PGA converts the differential to single end convertion with selectable gain of 20db, 40db, 60db.
After this PGA I am going to remove high frequency components and allowable range of 0 -30khz Band and remove other range of signals. Hence the Output of PGA will be 20Vpp.
Due to the Input Constraints of AD7768 (AD7768 – allow only Differential or pseudo- differential Input with maximum allowable Common mode range is 5Vpp).
hence I want to attenuate this signal 20-Vpp to 10-Vpp and Then ,I want to convert this single ended bipolar signal into differential bipolar as 5Vpp to match the AD7768.
Can you suggest any other part is available to attenuate and convert single end to differential conversion chip parts ?
Mr. Niall Suggest to use LTC6363 , In this Common mode input range is 8.8V as Max if 10V supply used. and also maximum power supply is 11V.
In ADA4940 , Power supply max is 7V and Common mode input will be −VS − 0.2 to +VS − 1.2.
Due to this constrain I couldn't able to move further,
In AD4922 have 26V as max Supply and Input common mode range ±10.7 , so that I asked your suggestion may I use this part .
Please let me know if you have any suggested part for attenuate and single end to differential end conversion.
Kindle let me know if you need any clarification regarding my inputs.