cancel
Showing results for 
Search instead for 
Did you mean: 

PSoC™ Creator & Designer

Anonymous
Not applicable

Hi, 

   

I am trying to use a Sample and hold component to hold constant a voltage in a circuit at certain times. The time period to hold the voltage isn't repetitive and is controlled from the API C code.

   

I tried doing this by setting the Sample and hold block "Sample clock edge" to "Negative" and the 'Sample mode" to "Sample and Hold".

   

I can't use use  a clock entrance for "sclk" because I don't want to sample in a repetitive interval. For the sclk input I created a logical control signal that is logical high before I need to hold the signal and is changed to logical low when I need to to Hold constant a new Value from the Vin input. 

   

This process repeats itself using a code loop that set the logical control signal to '1' in the beginning of each loop iteration

   

Unfortunately this doesn't seem to work and the Sample and Hold output seems to be stuck at a voltage close to 0V.

   

 

   

Do you have Any Idea how should I use the Sample and hold Component so that it would work properly?

   

 

   

Thanks

0 Likes
1 Solution
ETRO_SSN583
Esteemed Contributor

The S/H clock will go down to DC, so just use a control reg.

   

Not sure how you want to use it but suggest keep it sampling

   

until you want to go to hold, ie. use T/H mode. And keep in mind

   

the droop rate if you need to hold extended time.

   

 

   

Regards, Dana.

View solution in original post

0 Likes
4 Replies
ETRO_SSN583
Esteemed Contributor

The S/H clock will go down to DC, so just use a control reg.

   

Not sure how you want to use it but suggest keep it sampling

   

until you want to go to hold, ie. use T/H mode. And keep in mind

   

the droop rate if you need to hold extended time.

   

 

   

Regards, Dana.

View solution in original post

0 Likes
Anonymous
Not applicable

Thanks, It seems to work fine.

   

Do you know what is the droop rate that I should be expecting?

0 Likes
ETRO_SSN583
Esteemed Contributor

You can always use a A/D to effect a S/H, no droop issues. Especially effective

   

in applications that need very long hold times, no special low leakage caps

   

needed (for S/H).

   

 

   

You can also effect a long term S/H with analog mux and an OpAmp on in and out

   

of mux, and a cap of your choosing.

   

 

   

Regards, Dana.

0 Likes
ETRO_SSN583
Esteemed Contributor

I looked at component datasheet, droop rate spec shown w/o an entry.

   

You could always set up DelSig and measure it, or file a CASE and ask

   

for the spec.

   

 

   

To create a technical or issue case at Cypress -

   

 

   

www.cypress.com

   

“Design Support”

   

“Create a Support Case”

   

 

   

You have to be registered on Cypress web site first.

   

 

   

Regards, Dana.

0 Likes