AD7228A
REV. A
–4–
ABSOLUTE MAXIMUM RATINGS
1
VDD to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V, +17 V
VDD to VSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V, +24 V
Digital Input Voltage to GND . . . . . . . . . . . . . . . –0.3 V, VDD
VREF to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3V, VDD
VOUT to GND
2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V
SS, VDD
Power Dissipation (Any Package) to +75
°C . . . . . . . 1000 mW
Derates above 75
°C by . . . . . . . . . . . . . . . . . . . . 2.0 mW/°C
Operating Temperature
Commercial . . . . . . . . . . . . . . . . . . . . . . . . –40
°C to +85°C
Industrial . . . . . . . . . . . . . . . . . . . . . . . . . . –40
°C to +85°C
Extended . . . . . . . . . . . . . . . . . . . . . . . . . –55
°C to +125°C
Storage Temperature . . . . . . . . . . . . . . . . . . –65
°C to +150°C
Lead Temperature (Soldering, 10 secs) . . . . . . . . . . . +300
°C
NOTES
1Stresses above those listed under “Absolute Maximum Ratings” may cause
permanent damage to the device. This is a stress rating only and functional
operation of the device at these or any other conditions above those indicated in the
operational sections of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
2Outputs may be shorted to any voltage in the range V
SS to VDD provided that the
power dissipation of the package is not exceeded. Typical short circuit current for
a short to GND or VSS is 50 mA.
WARNING!
ESD SENSITIVE DEVICE
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the AD7228A features proprietary ESD protection circuitry, permanent damage may
occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD
precautions are recommended to avoid performance degradation or loss of functionality.
PIN CONFIGURATIONS
DIP AND SOIC
PLCC
ORDERING GUIDE
Total
Temperature
Unadjusted
Package
Model1
Range
Error (LSB)
Option2
AD7228ABN
–40
°C to +85°C
±2 max
N-24
AD7228ACN
–40
°C to +85°C
±1 max
N-24
AD7228ABP
–40
°C to +85°C
±2 max
P-28A
AD7228ACP
–40
°C to +85°C
±1 max
P-28A
AD7228ABR
–40
°C to +85°C
±2 max
R-24
AD7228ACR
–40
°C to +85°C
±1 max
R-24
AD7228ABQ
–40
°C to +85°C
±2 max
Q-24
AD7228ACQ
–40
°C to +85°C
±1 max
Q-24
AD7228ATQ
3
–55
°C to +125°C
±2 max
Q-24
AD7228AUQ
3
–55
°C to +125°C
±1 max
Q-24
NOTES
1To order MIL-STD-883, Class B processed parts, add /883B to part number.
Contact your local sales office for military data sheet and availability.
2N = Plastic DIP; P = Plastic Leaded Chip Carrier (PLCC); Q = Cerdip;
R = Small Outline IC (SOIC).
3These grades will be available to /883B processing only.
CIRCUIT INFORMATION
D/A SECTION
The AD7228A contains eight identical, 8-bit, voltage-mode
digital-to-analog converters. The output voltages from the con-
verters have the same polarity as the reference voltage, allowing
single supply operation. A novel DAC switch pair arrangement
on the AD7228A allows a reference voltage range from +2 V to
+10 V when operated from a VDD of +15 V. Each DAC consists
of a highly stable, thin-film, R-2R ladder and eight high-speed
NMOS switches. The simplified circuit diagram for one channel
is shown in Figure 3. Note that VREF and GND are common to
all eight DACs.
Figure 3. D/A Simplified Circuit Diagram
The input impedance at the VREF pin of the AD7228A is the
parallel combination of the eight individual DAC reference in-
put impedances. It is code dependent and can vary from 2 k
to
infinity. The lowest input impedance occurs when all eight
DACs are loaded with digital code 01010101. Therefore, it is
important that the external reference source presents a low out-
put impedance to the VREF terminal of the AD7228A under
changing load conditions. Due to transient currents at the refer-
ence input during digital code changes a 0.1
F (or greater)
decoupling capacitor is recommended on the VREF input for dc
applications. The nodal capacitance at the reference terminal is
also code dependent and typically varies from 120 pF to
350 pF.
Each VOUT pin can be considered as a digitally programmable
voltage source with an output voltage:
VOUTN = DN VREF
where DN is a fractional representation of the digital input
code and can vary from 0 to 255/256.
The output impedance is that of the output buffer amplifier as
described in the following section.