adc161s626cimmx National Semiconductor Corporation, adc161s626cimmx Datasheet - Page 14

• Manufacturer Part Number: adc161s626cimmx
• Description: 16-bit, 50 To 250 Ksps, Differential Input, Micropower Adc
• Manufacturer: National Semiconductor Corporation

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Both inputs should be biased at a common mode voltage
(V
ure 8 shows the ADC161S626 being driven by a full-scale
differential source.
2.2 Single-Ended Input Operation
For single-ended operation, the non-inverting input (+IN) of
the ADC161S626 can be driven with a signal that has a peak-
to-peak range that is equal to or less than (2 x V
inverting input (−IN) should be biased at a stable V
halfway between these maximum and minimum values. In
order
ADC161S626, V
maximum swing range of ground to V
ADC161S626 being driven by a full-scale single-ended
source.
Since the design of the ADC161S626 is optimized for a dif-
ferential input, the performance degrades slightly when driven
with a single-ended input. Linearity characteristics such as
INL and DNL typically degrade by 0.1 LSB and dynamic char-
acteristics such as SINAD typically degrade by 2 dB. Note that
single-ended operation should only be used if the perfor-
mance degradation (compared with differential operation) is
acceptable.
2.3 Input Common Mode Voltage
The allowable input common mode voltage (V
pends upon V
ranges of V
that these figures only apply to a V
culating the minimum and maximum V
single-ended operations are shown in Table 1.
CM
), which will be thoroughly discussed in Section 2.3. Fig-
to
CM
utilize
FIGURE 9. Single-Ended Input
A
are depicted in Figure 10 and Figure 11. Note
FIGURE 8. Differential Input
REF
and V
the
is limited to (V
REF
entire
used for the ADC161S626. The
dynamic
A
A
of 5V. Equations for cal-
/ 2). This allows +IN a
A
CM
. Figure 9 shows the
for differential and
30073481
range
30073480
CM
) range de-
REF
CM
of
). The
that is
the
14
2.4 CMRR
By using this differential input, small signals common to both
inputs are rejected. As shown in Figure 12, noise is immune
at low frequencies where the common-mode rejection ratio
(CMRR) is 90 dB. As the frequency increases to 1 MHz, the
CMRR rolls off to 40 dB . In general, operation with a fully
differential input signal or voltage will provide better perfor-
mance than with a single-ended input. However, if desired,
the ADC161S626 can be presented with a single-ended input.
Differential
Single-Ended
FIGURE 10. V
Input Signal
FIGURE 11. V
TABLE 1. Allowable V
CM
CM
range for Differential Input operation
range for single-ended operation
Minimum V
V
REF
V
REF
/ 2
CM
CM
Range
Maximum V
V
A
V
A
− V
30073461
30073462
− V
REF
REF
/ 2
CM