Data Sheet

ADA4500-2

Rev. A | Page 23 of 24

Besides converting the ac signal from single-ended to differential,

this circuit separates the ac and dc part of the input signal and

automatically adjusts the common-mode dc level of the output

differential version of the input signal with its common-mode

voltage set to an optimal value (such as, ½ the full-scale input

range to the ADC). The noninverted ac part of the signal is

output at OUTP, and the inverted ac signal is output at OUTN.

The differential output signal (OUTP to OUTN) is centered on

the voltage applied to REF. In this design, R3 and R4 set REF to

resistors can be eliminated, and the REF input can be driven

from an external source, such as a reference or the output of a

digital-to-analog converter (DAC).

using the voltage applied at REF and the voltage measured at the

signal known to the system, it can respond appropriately to, for

example, a situation when the common mode is getting too close to

the rails.

(2)

OUTP

U1A

ADA4500-2

R1B

1kΩ

R1A

1kΩ

C1

100pF

R2

2kΩ

C2

10pF

U2A

ADA4500-2

R11

5kΩ

INPUT

R6

10kΩ

R5

10kΩ

C5

0.01µF

C3

1µF

C7

1µF

C6

1µF

REF

OUTN

FB

R10

5kΩ

R9

5kΩ

R8

5kΩ

R4

100kΩ

R3

100kΩ

U2B

U1B

OUTPUT

INPUT

+2.5V

0V

+5V

+7.5V

+5V

+10V

–2.5V

–5V

0V

OR

OUTP

OUTN

OUTP

OUTN

Figure 66. Single-Ended-to-Differential Conversion Circuit Separates the AC and DC Part of the Signal