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AD7874 PIN FUNCTION DESCRIPTION

Pin

Mnemonic

Description

1

VIN1

Analog Input Channel 1. This is the first of the four input channels to be converted in a conversion cycle. Analog input voltage range is ± 10 V.

2

VIN2

Analog Input Channel 2. Analog input voltage range is ± 10 V.

3

VDD

Positive supply voltage, +5 V ± 5%. This pin should be decoupled to AGND.

4

INT

Interrupt. Active low logic output indicating converter status. See Figure 7.

5

CONVST

Convert Start. Logic Input. A low to high transition on this input puts the track/hold into its hold mode and starts conversion. The four channels are converted sequentially, Channel 1 to Channel 4. The CONVST input is asynchronous to CLK and independent of CS and RD.

6

RD

Read. Active low logic input. This input is used in conjunction with CS low to enable the data outputs. Four successive reads after a conversion will read the data from the four channels in the sequence, Channel 1, 2, 3, 4.

7

CS

Chip Select. Active low logic input. The device is selected when this input is active.

8

CLK

Clock Input. An external TTL-compatible clock may be applied to this input pin. Alternatively, tying this pin to VSS enables the internal laser trimmed clock oscillator.

9

VDD

Positive Supply Voltage, +5 V ± 5%. Same as Pin 3; both pins must be tied together at the package. This pin should be decoupled to DGND.

10

DB11

Data Bit 11 (MSB). Three-state TTL output. Output coding is 2s complement.

11–13

DB10–DB8

Data Bit 10 to Data Bit 8. Three-state TTL outputs.

14

DGND

Digital Ground. Ground reference for digital circuitry.

15–21

DB7–DB1

Data Bit 7 to Data Bit 1. Three-state TTL outputs.

22

DB0

Data Bit 0 (LSB). Three-state TTL output.

23

AGND

Analog Ground. Ground reference for track/hold, reference and DAC.

24

REF IN

Voltage Reference Input. The reference voltage for the part is applied to this pin. It is internally buffered, requiring an input current of only ± 1 µA. The nominal reference voltage for correct operation of the AD7874 is 3 V.

25

REF OUT

Voltage Reference Output. The internal 3 V analog reference is provided at this pin. To operate the AD7874 with internal reference, REF OUT is connected to REF IN. The external load capability of the reference is 500 µA.

26

VSS

Negative Supply Voltage, –5 V ± 5%.

27

VIN3

Analog Input Channel 3. Analog input voltage range is ± 10 V.

28

VIN4

Analog Input Channel 4. Analog input voltage range is ± 10 V. ORDERING GUIDE

Model1

Relative Temperature Range

SNR (dBs)

Accuracy (LSB)

Package Option2

AD7874AN AD7874BN AD7874AR AD7874BR AD7874AQ AD7874BQ AD7874SQ3 AD7874SE3

–40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –55°C to +125°C –55°C to +125°C

70 min 72 min 70 min 72 min 70 min 72 min 70 min 70 min

± 1 max ± 1/2 max ± 1 max ± 1/2 max ± 1 max ± 1/2 max ± 1 max ± 1 max

N-28 N-28 R-28 Q-28 Q-28 E-28A

NOTES 1 To order MIL-STD-883, Class B processed parts, add /883B to part number. Contact 1 our local sales office for military data sheet and availability. 2 E = Leaded Ceramic Chip Carrier; N = Plastic DIP; Q = Cerdip; R = SOIC. 3 Available to /883B processing only.

REV. C

–5–


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