ADL5569BCPZ-R7 datasheet(16/23 Pages) AD

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ADL5569

Data Sheet

Rev. C | Page 16 of 23

INPUT AND OUTPUT INTERFACING

The ADL5569 can be configured as a differential input to

differential output driver, as shown in Figure 40. The 50 Ω

resistors, R1 and R2, combined with the input balun, provide a

50 Ω input match for the 100 Ω input impedance. The input

and output 0.1 µF capacitors isolate the VVCC/VVCC2 bias from

the source and balanced load. The load is 100 Ω to provide the

expected ac performance (see the Specifications section).

0.1µF

1:1 BALUN

50Ω

ADL5569

½ RL

50Ω

0.1µF

–

Figure 40. Differential Input to Differential Output Configuration

The differential gain of the ADL5569 is dependent on the source

impedance and load, as shown in Figure 41. Determine the

differential gain (AV) by

AV = 500/50

(1)

ADL5569

0.1µF

50Ω

500Ω

0.1µF

–

Figure 41. Differential Input Loading Circuit

Single-Ended Input to Differential Output

The ADL5569 can also be configured in a single-ended input to

differential output configuration, as shown in Figure 42. In

this configuration, the gain of the device is reduced due to the

application of the signal to only one side of the amplifier. The input

and output 0.1 µF capacitors isolate the VVCC/VVCC2 bias from the

source and the balanced load.

The single-ended circuit configuration can be accomplished in

three steps (see Figure 42), assuming a 50 Ω RS source. First,

calculate the input resistance (RIN) of the amplifier using the

following formula:

(

)

1–













×+





(2)

where:

RG is the series resistance internal to the amplifier.

RF is feedback resistance internal to the amplifier.

Thus, RIN = 91.7 Ω.

The next step is to calculate the termination of Resistor R2 (see

Figure 42). Because source impedance (RS) must be equal to the

parallel equivalent resistance of R2 and RIN,

R2 R

Thus,

R2 = RIN × RS/(RIN − RS)

(3)

When RS = 50 Ω and RIN = 91.7 Ω, R2 = 109 Ω.

The last step is to calculate the gain path rebalancing resistor,

R1 (see Figure 42), by using the following formula:

(4)

Thus, R1 = 34.0 Ω.

ADL5569

50Ω

500Ω

0.1µF

–

Figure 42. Single-Ended Input to Differential Output Configuration

See the AN-0990 Application Note, Terminating a Differential

Amplifier in Single-Ended Input Applications, for more information

on terminating single-ended inputs. The single-ended gain

configuration of the ADL5569 is dependent on the source

impedance and load, as shown in Figure 43.

ADL5569

50Ω

500Ω

0.1µF

34.2Ω

0.1µF

109

–

Figure 43. Single-Ended Input Loading Circuit

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