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Hello TI, could you please clarify the following paragraph from Page 43 of the ADS62P22 datasheet?
ANALOG INPUT
The analog input consists of a switched-capacitor based differential sample and hold architecture.
This differential topology results in very good AC performance even for high input frequencies at high sampling
rates. The INP and INM pins have to be externally biased around a common-mode voltage of 1.5 V, available on
VCM pin 13. For a full-scale differential input, each input pin INP, INM has to swing symmetrically between VCM
+ 0.5 V and VCM – 0.5 V, resulting in a 2 V PP differential input swing. The maximum swing is determined by the
internal reference voltages REFP (2.5 V nominal) and REFM (0.5 V, nominal).
If VCM is 1.5V, then VCM +/- 0.5V gives an input range of 1V to 2V. Isn't this is a 1 VPP differential input, not 2 VPP?
Could you please confirm whether the actual input range is VCM +/- 1.0V, to give a 2 VPP differential input range from 0.5V to 2.5V, which matches the REFP and REFM figures listed?
Thank you for the clarification,
-Chris
Hey Chris,
You must take also take input INm into consideration when calculation differential input voltage range.
Vdiffpp = Vmax - Vmin
Where,
Vmax = INp - INm = 2V - 1V = 1V
Vmin = INm - INp = 1V - 2V = -1V
Vppdiff = 1V-(-1V) = 2Vpp
Hope that helps.
Yusuf