Datasheet

ADC12DC105
SNAS469A –SEPTEMBER 2008–REVISED OCTOBER 2008 www.ti.com
For single frequency sine waves the full scale error in LSB can be described as approximately:
E
FS
= 4096 ( 1 - sin (90° + dev))
where
• dev is the angular difference in degrees between the two signals having a 180° relative phase relationship to
each other (see Figure 19) (11)
For single frequency inputs, angular errors result in a reduction of the effective full scale input. For complex
waveforms, however, angular errors will result in distortion.
Figure 19. Angular Errors Between the Two Input Signals Will Reduce the Output Level or Cause
Distortion
It is recommended to drive the analog inputs with a source impedance less than 100Ω. Matching the source
impedance for the differential inputs will improve even ordered harmonic performance (particularly second
harmonic).
Table 1 indicates the input to output relationship of the ADC12DC105.
Table 1. Input to Output Relationship
V
IN
+
V
IN
−
Binary Output 2’s Complement Output
V
CM
− V
REF
/2 V
CM
+ V
REF
/2 00 0000 0000 00 10 0000 0000 00 Negative Full-Scale
V
CM
− V
REF
/4 V
CM
+ V
REF
/4 01 0000 0000 00 11 0000 0000 00
V
CM
V
CM
10 0000 0000 00 00 0000 0000 00 Mid-Scale
V
CM
+ V
REF
/4 V
CM
− V
REF
/4 11 0000 0000 00 01 0000 0000 00
V
CM
+ V
REF
/2 V
CM
− V
REF
/2 11 1111 1111 11 01 1111 1111 11 Positive Full-Scale
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