WM2331

Production Data

WOLFSON MICROELECTRONICS LTD

PD Rev 1.4 April 2001

12

AVDD/2

AVDD

AIN

MODE

REFSENSE

DC SOURCE =

AVDD/2 + [(+FS) - (-FS)] * GAIN/2

DC SOURCE =

AVDD/2 - [(+FS) - (-FS)] * GAIN/2

REFTF

REFBF

+FS

-FS

REFTS

REFBS

0.1µF

10µF

0.1µF

0.1µF

Figure 8 Full External Reference Mode (Reference Generator Disabled)

AVDD/2

AVDD

AIN

MODE

REFSENSE

REFTF

REFBF

+FS

-FS

REFTS

REFBS

-

+

+

-

REFT =

AVDD/2 + [(+FS) - (-FS)] * GAIN/2

REFB =

AVDD/2 - [(+FS) - (-FS)] * GAIN/2

0.1µF

10µF

0.1µF

0.1µF

0.1µF

0.1µF

Figure 9 Full External Mode with Kelvin connections (Reference Generator Disabled)

DIFFERENTIAL MODE (MODE = AVDD/2)

The WM2331 operates in differential mode when the voltage at the MODE pin is AVDD/2 (mid-

supply). The ADC reference voltages REFTF and REFBF are generated by the internal reference

on-chip reference generator or driven by an external source, as discussed under ‘On-chip Reference

Voltage Generation’, below. REFTF and REFBF are centred around AVDD/2 by the internal

SAMPLE

AND

HOLD

REFTS

REFBS

AIN

-1/2

+1

-1/2

PGA

REFTF

REFBF

ADC

CORE

INTERNAL

REFERENCE

BUFFER

= AVDD + VREF

2

= AVDD - VREF

2

VREF

AGND

Figure 10 ADC Reference Generation in Differential Mode

This mode is suitable for handling differentially presented inputs, which are applied to the AIN and

REFTS/REFBS pins. A special case of differential mode is centre span mode, in which the user

REFBS pins.