AD7769JP-REEL Analog Devices Inc, AD7769JP-REEL Datasheet - Page 7

• Manufacturer Part Number: AD7769JP-REEL
• Manufacturer: Analog Devices Inc

Specifications of AD7769JP-REEL

• Lead Free Status / Rohs Status: Supplier Unconfirmed

Plus and Minus Full-Scale Error
The ADC and DACs in the AD7769 can be considered as de-
vices with bipolar (plus and minus) input ranges, but referred to
V
difference between the actual input voltage at the FE to FF code
transition and the ideal input voltage (V
expressed in LSBs. Minus Full-Scale Error is similarly specified
for the 01 to 00 code transition, relative to the ideal input voltage
for this transition (V
Error for the DACs is the difference, expressed in LSBs, between
the actual output voltage for input code FF and the ideal voltage
(V
specified for code 00, relative to the ideal output voltage (V
V
ADC and the DAC outputs are measured after their respective
Bias Offset errors have been adjusted out.
Digital-to-Analog Glitch Impulse
Digital-to-Analog Glitch Impulse is the impulse injected into the
analog outputs when the digital inputs change state with either
DAC selected. It is normally specified as the area of the glitch in
nV secs and is measured when the digital input code is changed
by 1 LSB at the major carry transition.
Digital Feedthrough
Digital Feedthrough is also a measure of the impulse injected
into the analog outputs from the digital inputs but is measured
when the DACs are not selected. It is essentially feedthrough
across the die and package. It is important in the AD7769 since
it is a measure of the glitch impulse transferred to the analog
outputs when data is read from the ADC register. It is specified
in nV secs and is measured with WR high and a digital code
change from all 0s to all 1s.
REV. A
ADC CHANNEL SELECT AND START CONVERSION
CS
0
0
0
READ ADC DATA
CS
0
0
0
WRITE TO DACA OR DACB
CS
0
0
0
0
1
NOTES
1
2
3
If RD = 1, DB0–DB7 will remain high impedance. If RD = 0, DB0–DB7 will output previous ADC data. The RD input should not change during a conversion.
X = Don’t Care.
N/C = No Change.
BIAS
SWING
BIAS
instead of AGND. Plus Full-Scale Error for the ADC is the
+ V
). Note that Plus and Minus Full-Scale errors for the
ADC/DAC
0
0
0
ADC/DAC
X
X
X
ADC/DAC
1
1
1
1
X
SWING
– 1 LSB). Minus Full-Scale Error is similarly
BIAS
CHA/CHB
X
0
1
CHA/CHB
X
X
X
CHA/CHB
0
1
0
1
X
– V
SWING
+0.5 LSB). Plus Full-Scale
WR
WR
X
X
X
WR
X
BIAS
+ V
RD
Note 1
Note 1
Note 1
RD
0
RD
1
1
0
0
X
SWING
–1.5 LSB),
LOGIC TRUTH TABLE
DB0–DB7
Note 1
Note 1
Note 1
DB0–DB7
ADC Data
ADC Data
High-Z
DB0–DB7
ADC Data
ADC Data
High-Z
P Data
P Data
BIAS
–
–7–
INT
1
1
1
0
INT
1
1
1
INT
N/C
N/C
N/C
N/C
N/C
Signal-to-Noise Ratio (SNR)
SNR is the measured Signal-to-Noise Ratio at the output of the
converter. The signal is the rms magnitude of the fundamental.
Noise is the rms sum of all the nonfundamental signals up to
half the sampling frequency. SNR is dependent on the number
of quantization levels used in the digitization process; the more
levels, the smaller the quantization noise. The theoretical SNR
for a sine wave is given by
where N is the number of bits. Thus for an ideal 8-bit converter,
SNR = 49.92 dB.
Total Harmonic Distortion (THD)
THD is the ratio of the rms sum of harmonics to the fundamen-
tal. For the AD7769, Total Harmonic Distortion is defined as
where V
V
harmonics.
Intermodulation Distortion (IMD)
With inputs consisting of sine waves at two frequencies, f
f
products, of order (m+n), at sum and difference frequencies of
mf
those for which m or n is not equal to zero. For example, the
second order terms include (f
order terms include (2f
b
, any active device with nonlinearities will create distortion
3
, V
a
+nf
4
, V
b
Comments
INT Is Set on Falling Edge of WR.
Select ADC Channel A and Start Conversion.
Select ADC Channel B and Start Conversion.
INT Goes Low at End of Conversion.
Comments
INT Is Set High on Falling Edge of RD.
ADC Data on Data Bus.
Data Outputs Impedance.
Comments
Data from Last ADC Conversion Will Be Written to DACA.
Data from Last ADC Conversion Will Be Written to DACB.
No Operation.
, where m, n = 0, 1, 2, 3 . . . Intermodulation terms are
P Writing Data to DACA.
P Writing Data to DACB.
1
5
is the rms amplitude of the fundamental and V
and V
20 log
6
are the rms amplitudes of the individual
(V
2
a
2
SNR = (6.02N + 1.76) dB
+f
b
V
), (2f
3
2
a
+f
a
V
b
–f
) and (f
4
V
b
2
), (f
1
V
a
5
+2f
a
2
–f
b
b
V
) and the third
) and (f
6
2
AD7769
)
1/ 2
a
–2f
b
).
a
and
2
,