Analog Devices AD5259 Evaluation Board EVAL-AD5259DBZ EVAL-AD5259DBZ Data Sheet
Product codes
EVAL-AD5259DBZ
UG-392
Evaluation Board User Guide
Rev. 0 | Page 4 of 16
TEST CIRCUITS
The
and EVAL-MB-LV-SDZ incorporate
several test circuits to evaluate the performance of the
DAC
The RDAC can be operated as a digital-to-analog converter
(DAC), as shown in Figure 2.
(DAC), as shown in Figure 2.
VOUT1
R34
R35
A1
W1
RDAC
A
B
W
VDD
V
DD
AC+
V
DD
2
V
DD
2
AGND
BIAS
B1
BUF-W1
10620-
002
Figure 2. DAC
Table 5 shows the options available for the voltage references.
The output voltage is defined in Equation 1.
The output voltage is defined in Equation 1.
256
)
(
RDAC
V
V
V
B
A
OUT
×
−
=
(1)
where:
RDAC is the code loaded in the RDAC register.
V
A
is the voltage applied to the A terminal (A9 link).
V
B
is the voltage applied to the B terminal (A10 link).
However, by using the R34 and R35 external resistors, the user
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
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
A
and V
B
in Equation 1.
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.
provided externally using the AC_INPUT connector, as shown
in Figure 3.
VOUT1
R34
R35
A1
W1
RDAC
A
B
W
AC
AC+
AGND
BIAS
B1
BUF-W1
AC_INPUT
1kHz
HPF
10620-
003
V
DD
2
V
DD
2
Figure 3. AC Signal Attenuator
Depending on the voltage supply rails and the dc offset voltage
of the ac signal, various configurations can be used as described
in Table 4.
of the ac signal, various configurations can be used as described
in Table 4.
Table 4. AC Signal Attenuation Link Options
Link Options Conditions
A9
A9
AC+
No dc offset voltage.
AC signal is outside the voltage supply rails
due to the dc offset voltage.
due to the dc offset voltage.
DC offset voltage ≠ V
DD
/2
1
.
AC
All other conditions.
A10
BIAS
Use in conjunction with AC+ link
1
.
AGND
All other conditions.
1
Recommended to ensure optimal total harmonic distortion (THD) performance.
The signal attenuation is defined in Equation 2.
+
×
=
−
−
END
TO
END
W
WB
R
R
R
n
Attenuatio
log
20
)
dB
(
(2)
where:
R
WB
is the resistor between the W and B terminals.
R
W
is the wiper resistance.
R
END-TO-END
is the end-to-end resistance value.
Table 5. DAC Voltage References
Terminal
Link (Daughter Board)
Link (Motherboard)
Options
Description
A1
Switch B of A4
A9
AC+
Connects Terminal A1 to V
DD
/2
VDD
Connects Terminal A1 to V
DD
W1
Switch B of A3
BUF-W1
Connects Terminal W1 to an output buffer
B1
Switch B of A2
A10
BIAS
Connects Terminal B1 to V
DD
/2
AGND
Connects Terminal B1 to analog ground
A1 inserted
Closes feedback loop of second op amp in the