AD7874
P IN FUNCTIO N D ESCRIP TIO N
P in
Mnem onic
D escription
1
VIN1
Analog Input Channel 1. T his is the first of the four input channels to be converted in a con-
version cycle. Analog input voltage range is ±10 V.
2
3
4
5
VIN2
Analog Input Channel 2. Analog input voltage range is ±10 V.
VDD
Positive supply voltage, +5 V ± 5%. T his pin should be decoupled to AGND.
Interrupt. Active low logic output indicating converter status. See Figure 7.
INT
CONVST
Convert Start. Logic Input. A low to high transition on this input puts the track/hold into its
hold mode and starts conversion. T he four channels are converted sequentially, Channel 1 to
Channel 4. T he CONVST input is asynchronous to CLK and independent of CS and RD.
6
RD
Read. Active low logic input. T his 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.
7
8
CS
Chip Select. Active low logic input. T he device is selected when this input is active.
CLK
Clock Input. An external T T L-compatible clock may be applied to this input pin. Alterna-
tively, 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. T his pin should be decoupled to DGND.
10
DB11
Data Bit 11 (MSB). T hree-state T T L output. Output coding is 2s complement.
Data Bit 10 to Data Bit 8. T hree-state T T L outputs.
11–13
14
DB10–DB8
DGND
DB7–DB1
DB0
Digital Ground. Ground reference for digital circuitry.
Data Bit 7 to Data Bit 1. T hree-state T T L outputs.
15–21
22
Data Bit 0 (LSB). T hree-state T T L output.
23
AGND
Analog Ground. Ground reference for track/hold, reference and DAC.
24
REF IN
Voltage Reference Input. T he reference voltage for the part is applied to this pin. It is inter-
nally buffered, requiring an input current of only ±1 µA. T he nominal reference voltage for
correct operation of the AD7874 is 3 V.
25
REF OUT
Voltage Reference Output. T he internal 3 V analog reference is provided at this pin. T o oper-
ate the AD7874 with internal reference, REF OUT is connected to REF IN. T he external
load capability of the reference is 500 µA.
26
27
28
VSS
Negative Supply Voltage, –5 V ± 5%.
VIN3
VIN4
Analog Input Channel 3. Analog input voltage range is ±10 V.
Analog Input Channel 4. Analog input voltage range is ±10 V.
O RD ERING GUID E
Relative
Tem perature
Range
SNR
(dBs)
Accuracy
(LSB)
P ackage
O ption2
Model1
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
70 min
72 min
70 min
72 min
70 min
72 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
R-28
Q-28
Q-28
Q-28
E-28A
–55°C to +125°C 70 min
–55°C to +125°C 70 min
NOT ES
1T o order MIL-ST D-883, Class B processed parts, add /883B to part number. Contact
1our local sales office for military data sheet and availability.
2E = Leaded Ceramic Chip Carrier; N = Plastic DIP; Q = Cerdip; R = SOIC.
3Available to /883B processing only.
REV. C
–5–
ADI [ ADI ]
