THS1408-EP_14 Datasheet, PDF (17/28 Pages) Texas Instruments – 14-BIT, 3/8 MSPS DSP-COMPATIBLE ANALOG-TO-DIGITAL CONVERTER WITH INTERNAL REFERENCE AND PGA

THS1408-EP
14-BIT, 3/8 MSPS DSP-COMPATIBLE ANALOG-TO-DIGITAL CONVERTER
WITH INTERNAL REFERENCE AND PGA
SGLS129B − JULY 2002 − REVISED FEBRUARY 2010
APPLICATION INFORMATION
driving the analog input
The ADC has 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 (ΔIN) of the two input signals on IN+ and IN−.
22 Ω
100 pF
IN+
22 Ω
100 pF
THS1408
IN−
Figure 16. 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 ΔIN equals ΔREF, the negative full-scale output is reached, if ΔIN equals
−ΔREF.
ΔIN [V]
OUTPUT
−ΔREF
− full scale
0
0
ΔREF
+ full scale
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