Datasheet

Data Sheet AD7190
Rev. C | Page 23 of 40
CON23 CON22 CON21 CON20 CON19 CON18 CON17 CON16
Chop(0) 0(0) 0(0) REFSEL(0) 0(0) 0(0) 0(0) (0)
CON15
CON14
CON13
CON12
CON11
CON10
CON9
CON8
CH7(0) CH6(0) CH5(0) CH4(0) CH3(0) CH2(0) CH1(0) CH0(1)
CON7 CON6 CON5 CON4 CON3 CON2 CON1 CON0
Burn(0) REFDET(0) 0(0) BUF(1) U/
B
(0) G2(1) G1(1) G0(1)
Table 19. Configuration Register Bit Designations
Bit Location Bit Name Description
CON23 Chop Chop enable bit. When the chop bit is cleared, chop is disabled. When the chop bit is set, chop is
enabled. When chop is enabled, the offset and offset drift of the ADC are continuously minimized.
However, this increases the conversion time and settling time of the ADC. For example, when FS = 96
decimal and the sinc
4
filter is selected, the conversion time with chop enabled equals 80 ms and the
settling time equals 160 ms. With chop disabled, higher conversion rates are allowed. For an FS word of
96 decimal and the sinc
4
filter selected, the conversion time is 20 ms and the settling time is 80 ms.
However, at low gains, periodic calibrations may be required to remove the offset and offset drift.
CON22, CON21 These bits must be programmed with a Logic 0 for correct operation.
CON20 REFSEL Reference select bits. The reference source for the ADC is selected using these bits.
REFSEL Reference Voltage
0
External reference applied between REFIN1(+) and REFIN1(−).
1 External reference applied between the P1/REFIN2(+) and P0/REFIN2(-) pins.
CON19 to CON16
These bits must be programmed with a Logic 0 for correct operation.
CON15 to CON8 CH7 to CH0 Channel select bits. These bits are used to select which channels are enabled on the AD7190. See Table 20.
Several channels can be selected, and the AD7190 automatically sequences them. The conversion on
each channel requires the complete settling time.
CON7 Burn When this bit is set to 1, the 500 nA current sources in the signal path are enabled. When burn = 0, the
burnout currents are disabled. The burnout currents can be enabled only when the buffer is active and
when chop is disabled.
CON6 REFDET Enables the reference detect function. When set, the NOREF bit in the status register indicates when the
external reference being used by the ADC is open circuit or less than 0.6 V maximum. The reference
detect circuitry only operates when the ADC is active.
CON5 This bit must be programmed with a Logic 0 for correct operation.
CON4 BUF Enables the buffer on the analog inputs. If cleared, the analog inputs are unbuffered, lowering the
power consumption of the device. If set, the analog inputs are buffered, allowing the user to place
source impedances on the front end without contributing gain errors to the system. With the buffer
disabled, the voltage on the analog input pins can be from 50 mV below AGND to 50 mV above AV
DD
.
When the buffer is enabled, it requires some headroom; therefore, the voltage on any input pin must be
limited to 250 mV within the power supply rails.
CON3
U/
B
Polarity select bit. When this bit is set, unipolar operation is selected. When this bit is cleared, bipolar
operation is selected.
CON2 to CON0 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 (5 V Reference, Bipolar Mode)
0 0 0 1 ±5 V
0 0 1 Reserved
0 1 0 Reserved
0 1 1 8 ±625 mV
1 0 0 16 ±312.5 mV
1 0 1 32 ±156.2 mV
1 1 0 64 ±78.125 mV
1 1 1 128 ±39.06 mV