There is sample and hold in the sar adc,but i am not sure that i should feed a ramp wave or sine wave to the sample and hold?
Are there any relations to sar adc output and sample and hold input wave?
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\$\begingroup\$ Well what do you want to measure with the ADC? \$\endgroup\$– jramsay42Commented Nov 22, 2017 at 23:58
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1\$\begingroup\$ The sample and hold is to sample whatever waveform you are trying to digitize it, and hold it while the conversion is done. So as @jramsay42 said, feed it with the signal you want to measure or digitize. \$\endgroup\$– John DCommented Nov 23, 2017 at 0:17
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\$\begingroup\$ @jramsay42 I don't understand your meaning,can you take something for example? \$\endgroup\$– Shine SunCommented Nov 23, 2017 at 0:52
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\$\begingroup\$ The purpose of the sample and hold circuitry is to stop the analog waveform changing while it is being digitized by the ADC. It doesn't matter what that waveform actually is. If you are trying to measure a ramp wave, put in a ramp wave, if you are trying to measure a sine wave, put in a sine wave. \$\endgroup\$– jramsay42Commented Nov 23, 2017 at 1:06
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\$\begingroup\$ All sampling systems must have an input signal filter reject all signals >1/3 to 1/2 of sampling rate. This means an input blocking filter is needed but beware LPF filters also have group delay at the breakpoint. So a slow full scale sawtooth is good to test linearity and applying the ADC output to a DAC analog output allows you to check for all types of errors with dynamic inputs with the converted output. start with a slow triangle wave then try other inputs that match your source. A random step pulse will indicate other types of errors such as Capacitor memory issues etc. in the S&H. \$\endgroup\$– D.A.S.Commented Nov 23, 2017 at 1:49
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1 Answer
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Sample-and-hold has TWO input voltages (1) the squarewave (rectangular wave) rail-rail signal that opens/closes the sampling switch
(2) the voltage or waveform being sampled.
The datasheet will define min and max values for (1) and for (2).
answered Nov 23, 2017 at 19:44