Datasheet
AD7792/AD7793
Rev. B | Page 17 of 32
FS3 FS2 FS1 FS0 f
ADC
(Hz) t
SETTLE
(ms) 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.
Tabl e 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
Bias Voltage Generator Enable. The negative terminal of the analog inputs can be biased up to AV
DD
/2. These
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