THS1401 Datasheet, PDF (16/22 Pages) Texas Instruments – 14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS WITH INTERNAL REFERENCE AND PGA

THS1401, THS1403, THS1408
14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS
WITH INTERNAL REFERENCE AND PGA
SLAS248 – DECEMBER 1999
APPLICATION INFORMATION
driving the analog input
The THS1401/3/8 ADCs have a fully differential input. A differential input is advantageous with respect to SNR,
SFDR, and THD performance because the signal peak-to-peak level is 50% of a comparable single-ended
input.
There are three basic input configurations:
D Fully differential
D Transformer coupled single-ended to differential
D Single-ended
fully differential configuration
In this configuration, the ADC converts the difference (∆IN) of the two input signals on IN+ and IN–.
22 Ω
100 pF
IN+
22 Ω
100 pF
THS1401/3/8
IN–
Figure 19. Differential Input
The resistors and capacitors on the inputs decouple the driving source output from the ADC input and also serve
as first order low pass filters to attenuate out of band noise.
The input range on both inputs is 0 V to AV_DD. The full-scale value is determined by the voltage reference. The
positive full-scale output is reached, if ∆IN equals ∆REF, the negative full-scale output is reached, if ∆IN equals
–∆REF.
∆IN [V]
OUTPUT
–∆REF
– full scale
0
0
∆REF
+ full scale
16
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