THS1408-EP_14 Datasheet, PDF (18/28 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
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
100 pF
IN+
THS1408
IN− _CML
+
1 μF
0.1 μF
Figure 17. Transformer Coupled
The following table shows the input voltages for negative full-scale output, zero output, and positive full-scale output:
IN [V_PEAK]
−ΔREF
OUTPUT [_PEAK]
− full scale^†
0
0
ΔREF
+ 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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