AD7821
REV. B
–4–
ABSOLUTE MAXIMUM RATINGS*
V
DD
to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V, + 7 V
V
SS
to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . +0.3 V, + 7 V
Digital Input Voltage to GND
(Pins 6–8, 13) . . . . . . . . . . . . . . . . . . . –0.3 V, V
DD
+ 0.3 V
Digital Output Voltage to GND
(Pins 2–5, 9, 14–18) . . . . . . . . . . . . . . . –0.3 V, V
DD
+ 0.3 V
V
REF
(+) to GND . . . . . . . . . . . . . . . V
SS
– 0.3 V, V
DD
+ 0.3 V
V
REF
(–) to GND . . . . . . . . . . . . . . . V
SS
– 0.3 V, V
DD
+ 0.3 V
V
IN
to GND . . . . . . . . . . . . . . . . . . . V
SS
– 0.3 V, V
DD
+ 0.3 V
Operating Temperature Range
Commercial (K Version) . . . . . . . . . . . . . . –40°C to +85°C
Industrial (B Version) . . . . . . . . . . . . . . . . –40°C to +85°C
Extended (T Version) . . . . . . . . . . . . . . . –55°C to +125°C
Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C
Lead Temperature (Soldering, 10 sec) . . . . . . . . . . . . +300°C
Power Dissipation (Any Package) to +75°C . . . . . . . 450 mW
Derates above +75°C by . . . . . . . . . . . . . . . . . . . . . 6 mW/°C
*Stresses 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.
PIN CONFIGURATIONS
DIP AND SOIC LCCC PLCC
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 AD7821 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 FUNCTION DESCRIPTIONS
Pin Mnemonic Description
1V
IN
Analog Input: Range V
REF
(–) ≤ V
IN
≤ V
REF
(+)
2 DB0 Three-State Data Output (LSB)
3–5 DB1–DB3 Three-State Data Outputs
6 WR/RDY WRITE control input/READY status output. See Digital Interface section.
7 MODE Mode Selection Input. It determines whether the device operates in the WR-RD or RD mode. This input is internally
pulled low through a 50 µA current source. See Digital Interface section.
8 RD READ Input. RD must be low to access data from the part. See Digital Interface section.
9 INT INTERRUPT Output. INT going low indicates that the conversion is complete. INT returns high on the rising
edge of CS or RD. See Digital Interface section.
10 GND Ground
11 V
REF
(–) Lower limit of reference span.
Range: V
SS
≤ V
REF
(–) ≤ V
REF
(+).
12 V
REF
(+) Upper limit of reference span.
Range: V
REF
(–) < V
REF
(+) ≤ V
DD
.
13 CS Chip Select Input. The device is selected when this input is low.
14–16 DB4–DB6 Three-State Data Outputs
17 DB7 Three-State Data Output (MSB)
18 OFL Overflow Output. If the analog input is higher than (V
REF
(+) – 1/2 LSB), OFL will be low at the end of conversion. It
is a non-three-state output which can be used to cascade two or more devices to increase resolution.
19 V
SS
Negative Supply Voltage
V
SS
= 0 V; Unipolar Operation
V
SS
= –5 V; Bipolar Operation
20 V
DD
Positive Supply Voltage, +5 V
