ADS5102

ADS5103

SLAS351B – OCTOBER 2001 – REVISED DECEMBER 2001

19

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PRINCIPLES OF OPERATION

_

+

VO–

VO+

VOCM

THS4501

68 pF

68 pF

49.9

Ω

49.9

Ω

AIN–

AIN+

CML

ADS5102,

ADS5103

750

Ω

750

Ω

374

Ω

374

Ω

Digital

Outputs

V(source)

0.001

µF

0.1

µF

Figure 31. Driving the ADS5102/3 With Differential Amp (Gain = 2)

driving the analog input with a transformer

When little or no signal conditioning is required, a simple transformer is an excellent way to drive the input of

the ADS5102/3 family. The transformer provides single-ended to differential conversion and at frequencies

under 200 MHz produces very little distortion of the incoming signal. Figure 32 shows the preferred circuit

diagram for implementing a transformer-coupled input. The signal source is ac-coupled and fed to the primary

side of the RF transformer. Since the ADC input must be biased to the correct common mode voltage, the CML

output of the ADC is connected to the secondary center tap. It is recommended to provide decoupling capacitors

of 0.1

µF and 0.001 µF on the CML output. This filters out any high frequency noise prior the ADC input.

AIN–

AIN+

ADS5102,

ADS5103

V(source)

0.1

µF

0.001

µF

T1 – 1T-KK81

Mini-Circuits

49.9

Ω

0.1

µF

Digital

Outputs

CML

Figure 32. Driving the ADS5102/3 With a Transformer