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AD7821

REV. B

–4–

ABSOLUTE MAXIMUM RATINGS

VDD to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V, + 7 V

VSS to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . +0.3 V, + 7 V

Digital Input Voltage to GND

(Pins 6–8, 13) . . . . . . . . . . . . . . . . . . . –0.3 V, VDD + 0.3 V

Digital Output Voltage to GND

(Pins 2–5, 9, 14–18) . . . . . . . . . . . . . . . –0.3 V, VDD + 0.3 V

VREF(+) to GND . . . . . . . . . . . . . . . VSS – 0.3 V, VDD + 0.3 V

VREF(–) to GND . . . . . . . . . . . . . . . VSS – 0.3 V, VDD + 0.3 V

VIN to GND . . . . . . . . . . . . . . . . . . . VSS – 0.3 V, VDD + 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

Mnemonic Description

1VIN

Analog Input: Range VREF(–)

≤ V

REF(+)

DB0

Three-State Data Output (LSB)

3–5

DB1–DB3

Three-State Data Outputs

WR/RDY

WRITE control input/READY status output. See Digital Interface section.

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.

READ Input.

RD must be low to access data from the part. See Digital Interface section.

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.

GND

Ground

VREF(–)

Lower limit of reference span.

Range: VSS

≤ V

REF(–)

≤ V

REF(+).

VREF(+)

Upper limit of reference span.

Range: VREF(–) < VREF(+)

≤ V

DD.

Chip Select Input. The device is selected when this input is low.

14–16

DB4–DB6

Three-State Data Outputs

DB7

Three-State Data Output (MSB)

OFL

Overflow Output. If the analog input is higher than (VREF(+) – 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.

VSS

Negative Supply Voltage

VSS = 0 V; Unipolar Operation

VSS = –5 V; Bipolar Operation

VDD

Positive Supply Voltage, +5 V

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