voltage follower using switched capacitor block ASCxx

Tip / Sign in to post questions, reply, level up, and achieve exciting badges. Know more

cross mob
Anonymous
Not applicable

 hi developers,

   

                      i have a problem. i am trying to make a simple voltage follower using the switched capacitor block ASC10 as per the guidelines given in the application note AN2223 by dave. but i am not at all able to get it to work. the out put pulses for a moment to 2.5 V and settles at 1.2 V. Can anyone explain this behaviour. are the settings given correct. i have made all settings exactly the same as given the app note. but still i am not able to make it work. 

0 Likes
15 Replies
Bob_Marlowe
Level 10
Level 10
First like given 50 questions asked 10 questions asked

Hi Prasanna,

   

It is always better for us to have a look into your project. If you will, Zip (not RAW!) your project and upload it here. Maybe we can help you better.

   

 

   

Bob

0 Likes
Anonymous
Not applicable

 hi bob, i have attached the project

0 Likes
Bob_Marlowe
Level 10
Level 10
First like given 50 questions asked 10 questions asked

Not yet....

   

Bob

0 Likes
Anonymous
Not applicable

 bob i don't know what went wrong i can choose the zip file but its not getting posted.

0 Likes
Bob_Marlowe
Level 10
Level 10
First like given 50 questions asked 10 questions asked

Mail it directly to me: briefe@jmeiersoftware.de

   

 

   

Bob

0 Likes
Anonymous
Not applicable

 hi bob ,

   

          i have sent the project file to your mail. i have some observations which you can explain, when i test the circuit with no input wave form the output initially shoots up to 2.5V and then within 1ms it comes down to 1.3V. once it has reached 1.3 V it stays there forever. i tried to make a relaxation oscillator(asatble multivibrator) using this faux op-amp but then the square wave pattern is observable only for some 200us and again the output settles at 1.3 V.  what is this 1.3V.

0 Likes
lock attach
Attachments are accessible only for community members.
Bob_Marlowe
Level 10
Level 10
First like given 50 questions asked 10 questions asked

Received. (Sorry for the late post, lunchtime)

   

I see a mismatch between the global settings and the table of clock-frequencies in the application note. The clock is VC1 (6MHz) and the required settings should be Power: High and Bias High.

   

The settings of the amlifier do not correspond exactly thith the example given in the appnote.

   

The start of the amplifier is commented out  in main.c

   

 

   

Attached a corrected but untested project.

   

 

   

Bob

0 Likes
Anonymous
Not applicable

 thanks bob,

   

received the corrected project and tested. 

   

the out put still settles at 1.3 V. and it does not follow the input. what could be wrong

0 Likes
Bob_Marlowe
Level 10
Level 10
First like given 50 questions asked 10 questions asked

Oh, I didn't check it. The output P0_3 is set to strong and it must be set to "High Z Analog"

   

 

   

Bob

0 Likes
Anonymous
Not applicable

 hi bob, 

   

 a lot of thanks. its working perfect. i wrongly assumed that High Z Analog is for analog input pins just going by the name. i changed that pin settings now its fine. expect waveform art from me soon.

0 Likes
Bob_Marlowe
Level 10
Level 10
First like given 50 questions asked 10 questions asked

Great! One good deed a day!

   

So as Dave van Ess says: "May all the problems you have be the one you're paid for to solve!"

   

 

   

Bob

0 Likes
lock attach
Attachments are accessible only for community members.
Anonymous
Not applicable

Hi,

   

I'm new to PSoC, now I'm trying to make a voltage follower from SC as stated on the AN2223. When I tried to input a sine wave, it always have a voltage drop on the output, is there anyone now how to remove the drop?
here is my project too.

   

Help please. Thanks

0 Likes
lock attach
Attachments are accessible only for community members.
Bob_Marlowe
Level 10
Level 10
First like given 50 questions asked 10 questions asked

Your sample frequency is too high, the application note shows a max. frequ. of 4 MHz while you use VC1 which is SysClk / 1 which is in your case 24MHz

   

 

   

Bob

0 Likes
ETRO_SSN583
Level 9
Level 9
250 likes received 100 sign-ins 5 likes given

Keep in mind the analog output buffer does not drive to the rail -

   

 

   

www.cypress.com/     AN13666

   

 

   

Regards, Dana.

0 Likes
Anonymous
Not applicable

I've changed the maximum frequency now, but when I check the the input voltage of pin P2_1 and P2_3 with no input signal, both of the pins give 1,2 V . Is my psoc damaged ? or is the SC setting wrong?

   

thanks

0 Likes