# Non linearety ADL5565

Hello,

In my circuit i have an ADL5565 powerd by +/- 2.5Volt( see picture below) DC coupled .

When i apply a differential ramp voltage to the input( Pin 2: -0.5V...0.5V and Pin 3: 0.5V...-0.5V) i see a huge nonlinearety of +/- 75ppm.

I becomes smaller with a smaller input voltage:

Input           Output          Error

2Vpp_diff     4Vpp_diff     +/-75PPM

1Vpp_diff     2Vpp_diff     +/-30PPM

0.5Vpp_diff  1Vpp_diff     +/-11PPM

The shape of the non-linearety look like the picture below

An DC offset on the input does not influence the linearety.

Is this a know issue with the ADL5565 and is this frequency dependent?

In de datasheet there is not a lot of information about DC-couppled circuits.

I hope someone can tel me more about this issue

Thanks in advance foor any reaction

Dexter

• How is the paddle connected? Is it conneted to the -2.5 V supply or , is it floating?

What is the value of the load on the output?

Message was edited by: Jim Bedrosian

• The load is 400 ohm between the outputs (DC Coupled)

• From the plot supplied, it appears you have exceeded the 1 dB compression point of the amplifier.  (8Vp-p)

Please verify the input voltage is 2 V p-p. Can you supply output voltage plots for the other two conditions, 2 V p-p output and 1 V p-p output.

• Some mesurements:

The input voltage are aplied with a 16Bit resolution(X-axis of the plots input dac code)

Note about the "Error plot":

The error is shown as an endpoint line in LSB's of a 16Bit DAC.(1LSB= 15.25 ppm)

The 8Vpp signal shows some stange distortion on the output pins. I verified this with and osciliscope.

0.8Vpp_diff output Voltage ; Av=6 dB ; Rload = 400 ohm

Input signal on pin 2 and 3              Output Signal pin 10 and 11        Differential output signal

Error Plot .(1LSB= 15.25 ppm)

1Vpp_diff output Voltage ; Av=6 dB ; Rload = 400 ohm

Input signal on pin 2 and 3       utput Signal at pin 10 and 11       Differential output signal

Error Plot .(1LSB= 15.25 ppm)

2Vpp_diff output Voltage ; Av=6 dB ; Rload = 400 ohm

Input signal on pin 2 and 3       Output Signal at pin 10 and 11       Differential output signal

Error Plot .(1LSB= 15.25 ppm)

4Vpp_diff output Voltage ; Av=6 dB ; Rload = 400 ohm

Input signal on pin 2 and 3            Output Signal at pin 10 and 11      Differential output signal

Error Plot .(1LSB= 15.25 ppm)

8Vpp_diff output Voltage ; Av=6 dB ; Rload = 400 ohm

Input signal on pin 2 and 3                  Output Signal at pin 10 and 11       Differential output signal

Error Plot .(1LSB= 15.25 ppm)

• Attached is an oscilloscope plot of the ADL5565 with a signal swinging 8 V p-p at the output. With a signal that large the part is reaching its 1 dB compression point. This is why the signal is distorting.