AD7792/AD7793

Rev. B | Page 17 of 32

FS3

FS2

FS1

FS0

Rejection @ 50 Hz/60 Hz (Internal Clock)

1

0

0

1

16.7

120

80 dB (50 Hz only)

1

0

1

0

16.7

120

65 dB (50 Hz and 60 Hz)

1

0

1

1

12.5

160

66 dB (50 Hz and 60 Hz)

1

1

0

0

10

200

69 dB (50 Hz and 60 Hz)

1

1

0

1

8.33

240

70 dB (50 Hz and 60 Hz)

1

1

1

0

6.25

320

72 dB (50 Hz and 60 Hz)

1

1

1

1

4.17

480

74 dB (50 Hz and 60 Hz)

CONFIGURATION REGISTER

RS2, RS1, RS0 = 0, 1, 0; Power-On/Reset = 0x0710

The configuration register is a 16-bit register from which data can be read or to which data can be written. This register is used to con-

figure the ADC for unipolar or bipolar mode, enable or disable the buffer, enable or disable the burnout currents, select the gain, and

select the analog input channel. Table 17 outlines the bit designations for the filter register. CON0 through CON15 indicate the bit

locations; CON denotes that the bits are in the configuration register. CON15 denotes the first bit of the data stream. The number in

parentheses indicates the power-on/reset default status of that bit.

CON15

CON14

CON13

CON12

CON11

CON10

CON9

CON8

VBIAS1(0)

VBIAS0(0)

BO(0)

U/B(0)

BOOST(0)

G2(1)

G1(1)

G0(1)

CON7

CON6

CON5

CON4

CON3

CON2

CON1

CON0

REFSEL(0)

0(0)

0(0)

BUF(1)

0(0)

CH2(0)

CH1(0)

CH0(0)

Table 17. Configuration Register Bit Designations

Bit Location

Bit Name

Description

CON15 to

CON14

VBIAS1 to

VBIAS0

bits are used in conjunction with the boost bit.

VBIAS1

VBIAS0

Bias Voltage

0

0

Bias voltage generator disabled

0

1

Bias voltage connected to AIN1(

−)

1

0

Bias voltage connected to AIN2(

−)

1

1

Reserved

CON13

BO

Burnout Current Enable Bit. When this bit is set to 1 by the user, the 100 nA current sources in the signal path

are enabled. When BO = 0, the burnout currents are disabled. The burnout currents can be enabled only

when the buffer or in-amp is active.

CON12

U/B

Unipolar/Bipolar Bit. Set by user to enable unipolar coding; that is, zero differential input results in 0x000000

output, and a full-scale differential input results in 0xFFFFFF output. Cleared by the user to enable bipolar

coding. Negative full-scale differential input results in an output code of 0x000000, zero differential input

results in an output code of 0x800000, and a positive full-scale differential input results in an output code of

0xFFFFFF.

CON11

BOOST

This bit is used in conjunction with the VBIAS1 and VBIAS0 bits. When set, the current consumed by the bias

voltage generator is increased. This reduces its power-up time.

CON10 to

CON8

G2 to G0

Gain Select Bits.

Written by the user to select the ADC input range as follows:

G2

G1

G0

Gain

ADC Input Range (2.5 V Reference)

0

0

0

1 (In-amp not used)

2.5 V

0

0

1

2 (In-amp not used)

1.25 V

0

1

0

4

625 mV

0

1

1

8

312.5 mV

1

0

0

16

156.2 mV

1

0

1

32

78.125 mV

1

1

0

64

39.06 mV

1

1

1

128

19.53 mV