AD7874
PIN FUNCTION DESCRIPTION
Pin
1
2
3
4
5
Mnemonic
V
IN1
V
IN2
V
DD
INT
CONVST
Description
Analog Input Channel 1. This is the first of the four input channels to be converted in a con-
version cycle. Analog input voltage range is
±
10 V.
Analog Input Channel 2. Analog input voltage range is
±
10 V.
Positive supply voltage, +5 V
±
5%. This pin should be decoupled to AGND.
Interrupt. Active low logic output indicating converter status. See Figure 7.
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.
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 chan-
nels in the sequence, Channel 1, 2, 3, 4.
Chip Select. Active low logic input. The device is selected when this input is active.
Clock Input. An external TTL-compatible clock may be applied to this input pin. Alterna-
tively, tying this pin to V
SS
enables the internal laser trimmed clock oscillator.
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.
Data Bit 11 (MSB). Three-state TTL output. Output coding is 2s complement.
Data Bit 10 to Data Bit 8. Three-state TTL outputs.
Digital Ground. Ground reference for digital circuitry.
Data Bit 7 to Data Bit 1. Three-state TTL outputs.
Data Bit 0 (LSB). Three-state TTL output.
Analog Ground. Ground reference for track/hold, reference and DAC.
Voltage Reference Input. The reference voltage for the part is applied to this pin. It is inter-
nally buffered, requiring an input current of only
±
1
µA.
The nominal reference voltage for
correct operation of the AD7874 is 3 V.
Voltage Reference Output. The internal 3 V analog reference is provided at this pin. To oper-
ate the AD7874 with internal reference, REF OUT is connected to REF IN. The external
load capability of the reference is 500
µA.
Negative Supply Voltage, –5 V
±
5%.
Analog Input Channel 3. Analog input voltage range is
±
10 V.
Analog Input Channel 4. Analog input voltage range is
±
10 V.
ORDERING GUIDE
6
RD
7
8
9
10
11–13
14
15–21
22
23
24
CS
CLK
V
DD
DB11
DB10–DB8
DGND
DB7–DB1
DB0
AGND
REF IN
25
REF OUT
26
27
28
V
SS
V
IN3
V
IN4
Model
1
Relative
Temperature
Range
–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
SNR
(dBs)
70 min
72 min
70 min
72 min
70 min
72 min
70 min
70 min
Accuracy
(LSB)
±
1 max
±
1/2 max
±
1 max
±
1/2 max
±
1 max
±
1/2 max
±
1 max
±
1 max
Package
Option
2
N-28
N-28
R-28
R-28
Q-28
Q-28
Q-28
E-28A
AD7874AN
AD7874BN
AD7874AR
AD7874BR
AD7874AQ
AD7874BQ
AD7874SQ
3
AD7874SE
3
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–
AD [ ANALOG DEVICES ]
