MCP3553 ADC und sein Vref-Eingang

[Anselm 6. (anselm68)]

Hallöchen,

habe da eine kleine Unklarheit was die Behandlung der Vref betrifft.
Der Wandler hat einen differenziellen Eingang.
Hier mal die nicht so leicht für mich verständlichen Teile aus dem 
Datasheet:

3.1 Voltage Reference (VREF)
The MCP3550/1/3 devices accept single-ended reference
voltages from 0.1V to VDD. Since the converter
output noise is dominated by thermal noise, which is
independent of the reference voltage, the output noise
is not significantly improved by diminishing the reference
voltage at the VREF input pin. A reduced voltage
reference will significantly improve the INL performance
(see Figure 2-4); the INL max error is
proportional to VREF²

4.5 Voltage Reference Input Pin
The MCP3550/1/3 devices accept a single-ended
external reference voltage, to be connected on the
VREF input pin. Internally, the reference voltage for the
ADC is a differential voltage with the non-inverting input
connected to the VREF pin and the inverting input
connected to the VSS pin. The value of the reference
voltage is VREF - VSS and the common mode of the
reference is always (VREF - VSS)/2.
The MCP3550/1/3 devices accept a single-ended
reference voltage from 0.1V to VDD. The converter
output noise is dominated by thermal noise that is
independent of the reference voltage. Therefore, the
output noise is not significantly improved by lowering
the reference voltage at the VREF input pin. However, a
reduced reference voltage will significantly improve the
INL performance since the INL max error is
proportional to VREF
2 (see Figure 2-4).
The charge and discharge of the input capacitor create
dynamic input currents at the VREF input pin inversely
proportional to the sampling capacitor, which is a function
of the input reference voltage. The typical value of
the single-ended input impedance is 2.4 MΩ, with
VDD = VREF = 5V. The DC leakage current caused by
the ESD input diodes, though on the order of 1 nA
typically, can cause additional gain error proportional to
the source resistance at the VREF pin.

Ich habe eine Vref mit 4,096V geplant.
welche Spannung kann er damit messen???
4Volt?
oder wegen dem (...the common mode of the
reference is always (VREF - VSS)/2.) nur 2,048?

Vielleicht kann mich jemand ja aufklären ;)

Habt Dank im vorraus
Anselm

p.S.: Vin- an GND/VSS angeschlossen
      Vin+ am Ausgang des Messverstärkers
Datenblatt zu finden unter: 
http://ww1.microchip.com/downloads/en/DeviceDoc/21950d.pdf