THS1401-EP THS1403-EP THS1408-EP

14-BIT, 1/3/8 MSPS DSP COMPATIBLE ANALOG-TO-DIGITAL CONVERTERS

WITH INTERNAL REFERENCE AND PGA

SGLS129A – JULY 2002 – REVISED NOVEMBER 2002

18

POST OFFICE BOX 655303

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.

100 pF

IN+

IN–

THS1401/3/8

CML

R

100 pF

22

Ω

22

Ω

+

1

µF

0.1

µF

Figure 20. Transformer Coupled

The following table shows the input voltages for negative full-scale output, zero output, and positive full-scale output:

IN [VPEAK]

OUTPUT [PEAK]

–

∆REF

– 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