Rainbow Electronics MX7705 - Manual (Page 31)

Definitions
Integral Nonlinearity
Integral nonlinearity (INL) is the deviation of the values
on an actual transfer function from a straight line. This
straight line is either a best-straight-line fit or a line
drawn between the endpoints of the transfer function,
once offset and gain errors have been nullified. INL for
the MX7705 is measured using the endpoint method.
This is the more conservative method.
Unipolar Offset Error
For an ideal converter, the first transition occurs at 0.5
LSB above zero. Offset error is the amount of deviation
between the measured first transition point and the
ideal point.
Bipolar Zero Error
In bipolar mode, the ideal midscale transition occurs at
AIN+ - AIN- = 0. Bipolar zero error is the measured
deviation from this ideal value.
Gain Error
With a full-scale analog input voltage applied to the
ADC (resulting in all ones in the digital code), gain error
is defined as the amount of deviation between the ideal
transfer function and the measured transfer function
(with the offset error or bipolar zero error removed).
Gain error is usually expressed in LSB or a percent of
full-scale range (%FSR).
Positive Full-Scale Error
For the ideal transfer curve, the code edge transition
that causes a full-scale transition to occur is 1.5 LSB
below full scale. The positive full-scale error is the dif-
ference between this code transition of the ideal trans-
fer function and the actual measured value at this code
transition. Unlike gain error, unipolar offset error and
bipolar zero error are included in the positive full-scale
error measurement.
Bipolar Negative Full-Scale Error
For the ideal transfer curve, the code edge transition that
causes a negative full-scale transition to occur is 0.5 LSB
above negative full scale. The negative full-scale error is
the difference between this code transition of the ideal
transfer function and the actual measured value at this
code transition.
Input Common-Mode Rejection
Input common-mode rejection (CMR) is the ability of a
device to reject a signal that is common to or applied to
both input terminals. The common-mode signal can be
either an AC or a DC signal or a combination of the two.
CMR is often expressed in decibels. Common-mode
rejection ratio (CMRR) is the ratio of the differential sig-
nal gain to the common-mode signal gain.
Power-Supply Rejection Ratio
Power-supply rejection ratio (PSRR) is the ratio of the
input signal change (V) to the change in the converter
output (V). It is typically measured in decibels.
Chip Information
TRANSISTOR COUNT: 42,000
PROCESS: BiCMOS
MX7705
16-Bit, Low-Power, 2-Channel,
Sigma-Delta ADC
______________________________________________________________________________________ 31
MX7705
DIN
V CC
6N136
2k Ω
470k Ω
SCLK
DOUT
CS
MOSI
SCK
MISO
CS
ISO
3V/5V
V CC
6N136
2k Ω
470k Ω
V CC
6N136
470k Ω 2k Ω
+V DD
V DD
Figure 14. Optically Isolated Interface