Preliminary Technical Data

AD7190

Rev.PrD 7/08 | Page 19

CONFIGURATION REGISTER

(RS2, RS1, RS0 = 0, 1, 0; Power-On/Reset = 0x000117)

The configuration register is a 24-bit register from which data can be read or to which data can be written. This register is used to

configure 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 18 outlines the bit designations for the filter register. CON0 through CON23 indicate the bit locations. CON denotes that the bits

are in the configuration register. CON23 denotes the first bit of the data stream. The number in brackets indicates the power-on/reset

default status of that bit.

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)

GN2(1)

GN1(1)

GN0(1)

Table 18. Configuration Register Bit Designations

Bit

Location

Bit Name

Description

CON23

CHOP

Chop Enable Bit.

When CHOP is cleared, chop is disabled.

When CHOP is set, chop is disabled.

When chop is enabled, the offset and offset drift is continuously removed by the ADC. However, it

increases the conversion time and settling time of the ADC. For example, when FS = 96 decimal and the

160 ms. With chop disabled, higher conversion rates are allowed. For an SF word of 96 decimal and the

periodic calibrations may be required to remove the offset and offset drift.

CON22,

CON21

0

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 and P0 pins.

CON19 to

CON16

0

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 19. Several channels

can be selected and the AD7190 will automatically sequence between them. The conversion on each

channel will require the complete settling time.

CON7

BURN

When this bit is set to 1 by the user, 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.

CON6

REFDET

Enables the Reference Detect Function.

When set, the NOXREF bit in the status register indicates when the external reference being used by the

ADC is open circuit or less than 0.5 V.

CON5

0

This bit must be programmed with a Logic 0 for correct operation.

CON4

BUF

Configures the ADC for buffered or unbuffered mode of operation. If cleared, the ADC operates in

unbuffered mode, lowering the power consumption of the device. If set, the ADC operates in buffered

mode, 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 GND to 50 mV

be limited to 200 mV within the power supply rails.