Test Circuits - Analog Devices EVAL-AD5165DBZ User Manual

UG-629

TEST CIRCUITS

The EVAL-AD5165DBZ
several test circuits to evaluate the performance of the AD5165.
DAC
The RDAC can be operated as a digital-to-analog converter
(DAC), as shown in Figure 2.
AC+
V
DD
2
VDD
V
DD
R34
RDAC
A
W
B
R35
BIAS
V
DD
2
AGND
Table 4 shows the options available for the voltage references.
The output voltage is defined in Equation 1.
= −
V ( V V )
OUT A B
where:
RDAC is the code loaded in the RDAC register.
V is the voltage applied to the A terminal (A9 link).
A
V is the voltage applied to the B terminal (A10 link).
B
However, by using the R34 and R35 external resistors, you can
reduce the voltage of the voltage references. In this case, use the
A1 and B1 test points to measure the voltage applied to the A and
B terminals and recalculate V
AC Signal Attenuation
The RDAC can be used to attenuate an ac signal, which must be
provided externally using the AC_INPUT connector, as shown
in Figure 3.
Table 4. DAC Voltage References
Terminal Daughter Board
A1 P5: A1 position
W1 P6: W1 position
B1 P7: B1 position
P8: inserted
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and EVAL-MB-LV-SDZ incorporate
A1
W1
VOUT1
BUF-W1
B1
Figure 2. DAC
RDAC
×
256
and V in Equation 1.
A B
Link Settings
Motherboard
A9: AC+ position
A9: VDD position
BUF-W1: inserted
A10: BIAS position
A10: AGND position
EVAL-AD5165DBZ User Guide
1kHz
HPF
AC_INPUT
Depending on the voltage supply rails and the dc offset voltage
of the ac signal, various configurations can be used, as described
in Table 3.
Table 3. AC Signal Attenuation Link Options
Link Options
A9 AC+
(1) AC
A10 BIAS
AGND
Recommended to ensure optimal total harmonic distortion (THD) performance.
1
The signal attenuation is defined in Equation 2.
Attenuatio n
where:
R is the resistance between the W and B terminals.
WB
R is the wiper resistance.
W
R is the end-to-end resistance value.
END-TO-END
Description
Connects Terminal A1 to V /2
DD
Connects Terminal A1 to V
DD
Connects Terminal W1 to an output buffer
Connects Terminal B1 to V /2
DD
Connects Terminal B1 to analog ground
Closes the feedback loop of the second op amp in the
Rev. 0 | Page 4 of 16
V
DD
2
AC+
AC
R34
A1
RDAC
A
W1
W
BUF-W1
B
B1
R35
BIAS
V
DD
2
AGND
Figure 3. AC Signal Attenuator
Conditions
No dc offset voltage.
AC signal is outside the voltage supply rails
due to the dc offset voltage.
DC offset voltage ≠ V /2. 1
DD
All other conditions.
Use in conjunction with AC+ link.
All other conditions.
 
+
R R
 
= × WB W
( dB ) 20 log
 
R
 
− −
END TO END
AD8618
VOUT1
1
(2)