I have a question about the need for an external sample and hold circuit for certain SAR type A/D converters.
Referring to the datasheet for a part like the ADS7822 or ADS8320 http://www.ti.com/lit/ds/symlink/ads8320.pdf, the theory of operation section makes a statement about the architecture inherently including a sample and hold function. Does this mean the chip performs sample and hold of the analog input internally and there is no requirement for or benefit from an external sample and hold circuit?
If so, how does the architecture of these parts differ in terms of the sample and hold functionality from a part like the ADS8327? http://www.ti.com/lit/ds/symlink/ads8327.pdf