Datasheet AD7874 (Analog Devices) - 6

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 con- version 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 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 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 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 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 Relative Temperature SNR Accuracy Package Model1 Range (dBs) (LSB) Option2
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 AD7874SQ3 –55°C to +125°C 70 min ±1 max Q-28 AD7874SE3 –55°C to +125°C 70 min ±1 max E-28A NOTES 1To order MIL-STD-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–