AD7874 Analog Devices, AD7874 Datasheet - Page 5

• Manufacturer Part Number: AD7874
• Description: LC2MOS 4-Channel/ 12-Bit Simultaneous Sampling Data Acquisition System
• Manufacturer: Analog Devices

REV. C
PIN FUNCTION DESCRIPTION
Pin
1
2
3
4
5
6
7
8
9
10
11–13
14
15–21
22
23
24
25
26
27
28
Mnemonic
V
V
V
INT
CONVST
RD
CS
CLK
V
DB11
DB10–DB8
DGND
DB7–DB1
DB0
AGND
REF IN
REF OUT
V
V
V
IN1
IN2
DD
DD
SS
IN3
IN4
Model
AD7874AN
AD7874BN
AD7874AR
AD7874BR
AD7874AQ
AD7874BQ
AD7874SQ
AD7874SE
NOTES
1
1
2
3
To order MIL-STD-883, Class B processed parts, add /883B to part number. Contact
our local sales office for military data sheet and availability.
E = Leaded Ceramic Chip Carrier; N = Plastic DIP; Q = Cerdip; R = SOIC.
Available to /883B processing only.
1
3
3
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
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
Positive Supply Voltage, +5 V
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 A. 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 A.
Negative Supply Voltage, –5 V
Analog Input Channel 3. Analog input voltage range is 10 V.
Analog Input Channel 4. Analog input voltage range is 10 V.
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
ORDERING GUIDE
SS
–5–
SNR
(dBs)
70 min
72 min
70 min
72 min
70 min
72 min
70 min
70 min
enables the internal laser trimmed clock oscillator.
5%. This pin should be decoupled to AGND.
5%. Same as Pin 3; both pins must be tied together at the
5%.
Accuracy
(LSB)
1 max
1/2 max
1 max
1/2 max
1 max
1/2 max
1 max
1 max
Package
Option
N-28
N-28
R-28
R-28
Q-28
Q-28
Q-28
E-28A
2
AD7874