Datasheet

UG-274 Evaluation Board User Guide
Rev. 0 | Page 4 of 16
TEST CIRCUITS
The E VA L-AD5252SDZ incorporates several test circuits to
evaluate the AD5252 performance.
DAC
RDAC1 can be operated as a digital-to-analog converter (DAC),
as shown in Figure 2.
09820-002
W1_BUF
A1
RDAC1
AC + DC
VDD
A1
B1
BUF-W1
VSS
GND
DC
2
V
DD
– V
SS
V
DD
2
V
DD
– V
SS
V
SS
R34
R35
W1
W1
B1
Figure 2. DAC
Table 4 shows the options available for the voltage references.
Table 4. DAC Voltage References
Terminal Link Options Description
A1 A20 AC + DC Connects Terminal A1 to
(V
DD
− V
SS
)/2.
VDD Connects Terminal A1 to V
DD
.
W1 BUF-W1 Connects Terminal W1 to an
output buffer.
B1 A21 DC Connects Terminal B1 to
(V
DD
− V
SS
)/2.
VSS Connects Terminal B1 to V
SS
.
GND Connects Terminal B1 to
analog ground.
The output voltage is defined in Equation 1.
256
)(
WB1
B1
A1
OUT
R
VVV ×−=
(1)
where:
R
WB1 is the resistor between the W1 and B1 terminals.
V
A1
is the voltage applied to the A1 terminal (A20 link).
V
B1
is the voltage applied to the B1 terminal (A21 link).
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 A1 and B1
terminals and recalculate V
A1
and V
B1
in Equation 1.
AC Signal Attenuation
RDAC1 can be used to attenuate an ac signal, which must be
provided externally using the AC_INPUT connector, as shown
in Figure 3.
W1_BUF
A1
RDAC1
AC + DC
AC_INPUT
AC
A1
B1
BUF-W1
GND
2
V
DD
– V
SS
V
SS
R34
R35
W1
W1
B1
1µF
R36
09820-003
DC
VSS
2
V
DD
– V
SS
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 5.
Table 5. AC Signal Attenuation Link Options
Voltage
Supply
Maximum
AC Signal
Amplitude
Link Options Conditions
Single V
DD
A20 AC + DC No dc offset voltage.
AC signal is outside
the voltage supply
rails due to the
dc offset voltage.
DC offset voltage
≠ V
DD
/2
1
.
AC All other conditions.
A21 DC Use in conjunction
with AC + DC link.
GND All other conditions.
Dual V
DD
/V
SS
A20 AC + DC AC signal is outside
the voltage supply
rails due to the
dc offset voltage.
DC offset voltage
≠ 0 V
1
.
AC All other conditions.
A21 GND Use in conjunction
with AC + DC link.
VSS All other conditions.
1
Recommended to ensure optimal total harmonic distortion (THD) performance.
The signal attenuation is defined in Equation 2.








+
×=
−− ENDTOEND
WWB1
R
RR
nAttenuatio log20)dB(
(2)
where:
R
WB1
is the resistor between the W1 and B1 terminals.
R
W
is the wiper resistance.
R
END-TO-END
is the end-to-end resistance value.