Test Circuits - Analog Devices EVAL-AD51150SDZ User Manual

UG-322

TEST CIRCUITS

The EVAL-AD5110SDZ incorporates several test circuits to
evaluate the AD5110 performance.
DAC
The AD5110 can be operated as a digital-to-analog converter
(DAC), as shown in Figure 2.
AC
V
DD
2
DC
V
DD
R9
A
A
W
W
B
B
R8
AC
V
DD
2
GND
Figure 2. DAC
Table 4 shows the options available for the voltage references.
Table 4. DAC Voltage References
Terminal Link Options
A LK1 AC
DC
W BUF-W
B LK6 AC
GND
The output voltage is defined in Equation 1.
RDAC
= − ×
V V V
( )
OUT A B
256
where:
RDAC is the code loaded in the RDAC register.
V is the voltage applied to Terminal A (LK1 link).
A
V is the voltage applied to Terminal B (LK6 link).
B
However, by using the R8 and R9 external resistors, the user can
reduce the voltage of the voltage references. In this case, use the
A and B test points to measure the voltage applied to the A and
B terminals and recalculate V
750Ω
– 12Ω
VOUT
+
BUF-W
Description
Connects Terminal A to V
Connects Terminal A to V
Connects Terminal W to an
output buffer
Connects Terminal B to V
Connects Terminal B to
analog ground
and V in Equation 1.
A B
AC Signal Attenuation
The AD5110 can be used to attenuate an ac signal, which must
be provided externally using the AC_INPUT connector, as
shown in Figure 3.
AC_INPUT
HPF
f
= 200Hz
C
Depending on the voltage supply rails and the dc offset voltage
of the ac signal, various configurations can be used as described
in Table 5.
Table 5. AC Signal Attenuation Link Options
Terminal Link
A LK1
/2
DD
DD
W BUF-W
B LK6
/2
DD
1 Recommended to ensure optimal total harmonic distortion (THD) performance.
The signal attenuation is defined in Equation 2.
(1)
Attenuatio
where:
RDAC is the code loaded in the RDAC register.
In addition, R7 can be used to achieve an exponential attenua-
tion. To do so, adjust the R7 resistor until a desirable transfer
function is found, typically around 1.6 kΩ for a 10 kΩ
potentiometer.
Rev. 0 | Page 4 of 12
Evaluation Board User Guide
V
DD
2
AC
R9
A
A
BUF-W
W
W
R7
B
B
R8
AC
V
DD
2
GND
Figure 3. AC Signal Attenuator
Options Description
AC Remove dc voltage and biased
the signal to V
Connects Terminal W to an
output buffer
AC 1 Connects Terminal B to V
GND Connects Terminal B to analog
ground
RDAC
 
≈ ×
n ( dB ) 20 log
 
 
128
750Ω
12Ω
–
VOUT
+
/2
DD
/2
DD
(2)