THS1401 Datasheet, PDF (17/22 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
transformer coupled single-ended to differential configuration
If the application requires the best SNR, SFDR, and THD performance, the input should be transformer coupled.
The signal amplitude on both inputs of the ADC is one half as high as in a single-ended configuration thus
increasing the ADC ac performance.
22 Ω
R
22 Ω
100 pF ^IN+
THS1401/3/8
100 pF
IN– _CML
+
1 µF
0.1 µF
Figure 20. Transformer Coupled
IN [VPEAK]
–∆REF
OUTPUT [PEAK]
– full scale†
0
0
∆REF
+ full scale†
† _{n = 1 (winding ratio)}
The resistor R of the transformer coupled input configuration must be set to match the signal source impedance
R = n² Rs, where Rs is the source impedance and n is the transformer winding ratio.
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