AD7985BCPZ(Rev0) View Datasheet(PDF) - Analog Devices

Part Name

Description

MFG CO.

AD7985BCPZ
(Rev.:Rev0)

16-Bit, 2.5 MSPS, PulSAR 15.5 mW ADC in LFCSP

Analog Devices 

AD7985

Transfer Functions

The ideal transfer characteristic for the AD7985 is shown in

Figure 22 and Table 7.

111 ... 111

111 ... 110

111 ... 101

000 ... 010

000 ... 001

000 ... 000

–FSR

–FSR + 1 LSB

+FSR – 1 LSB

–FSR + 0.5 LSB

+FSR – 1.5 LSB

ANALOG INPUT

Figure 22. ADC Ideal Transfer Function

Table 7. Output Codes and Ideal Input Voltages

Description

Analog Input,

VREF = 4.096 V

Digital Output

Code (Hex)

FSR – 1 LSB

4.095938 V

0xFFFF1

Midscale + 1 LSB 2.048063 V

0x8001

Midscale

2.048 V

0x8000

Midscale – 1 LSB 2.047938 V

0x7FFF

–FSR + 1 LSB

62.5 μV

0x0001

–FSR

0V

0x00002

1 This is also the code for an overranged analog input (VIN+ − VIN− above VREF −

REFGND).

2 This is also the code for an underranged analog input (VIN+ − VIN− below REFGND).

TYPICAL CONNECTION DIAGRAM

Figure 23 shows an example of the recommended connection

diagram for the AD7985 when multiple supplies are available.

1.8V

TO

5V 2.5V 2.7V

0V TO VREF

V+

BVDD AVDD, VIO

15Ω

DVDD TURBO

IN+

SDI

2.7nF

IN–

AD7985 SCK

V–

SDO

REF GND

CNV

VIO

3- OR 4-WIRE

INTERFACE:

SPI, CS,

DAISY CHAIN

(TURBO = LOW)

10µF

NOTES

1. GND REFERS TO REFGND, AGND, AND DGND.

Figure 23. Typical Application Diagram with Multiple Supplies

Rev. 0 | Page 14 of 28

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