Datasheet

AD7874
REV. C
–5–
PIN FUNCTION DESCRIPTION
Pin Mnemonic Description
1V
IN1
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.
2V
IN2
Analog Input Channel 2. Analog input voltage range is ±10 V.
3V
DD
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 chan-
nels 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. Alterna-
tively, tying this pin to V
SS
enables the internal laser trimmed clock oscillator.
9V
DD
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 inter-
nally 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 oper-
ate the AD7874 with internal reference, REF OUT is connected to REF IN. The external
load capability of the reference is 500 µA.
26 V
SS
Negative Supply Voltage, –5 V ± 5%.
27 V
IN3
Analog Input Channel 3. Analog input voltage range is ±10 V.
28 V
IN4
Analog Input Channel 4. Analog input voltage range is ±10 V.
ORDERING GUIDE
Relative
Temperature SNR Accuracy Package
Model
1
Range (dBs) (LSB) Option
2
AD7874AN –40°C to +85°C 70 min ±1 max N-28
AD7874BN –40°C to +85°C 72 min ±1/2 max N-28
AD7874AR –40°C to +85°C 70 min ±1 max R-28
AD7874BR –40°C to +85°C 72 min ±1/2 max R-28
AD7874AQ –40°C to +85°C 70 min ±1 max Q-28
AD7874BQ –40°C to +85°C 72 min ±1/2 max Q-28
AD7874SQ
3
–55°C to +125°C 70 min ±1 max Q-28
AD7874SE
3
–55°C to +125°C 70 min ±1 max 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.