WM2631

Production Data

WOLFSON MICROELECTRONICS LTD

PD Rev 1.1 April 2001

8

DEVICE DESCRIPTION

GENERAL FUNCTION

The WM2631 is an octal 10-bit, voltage output DAC. It contains a serial interface, control logic for

speed and power down, a programmable voltage reference, and eight digital to analogue converters.

Each converter uses a resistor string network buffered with an op amp to convert 10-bit digital data to

analogue voltage levels (see Block Diagram). The output voltage is determined by the reference

input voltage and the input code according to the following relationship:

Output voltage =

()

1024

2

CODE

INPUT

OUTPUT

11 1111 1111

()

1024

1023

2

REF

V

::

10 0000 0001

()

1024

511

2

REF

V

10 0000 0000

()

REF

REF

V

V

=

1024

512

2

01 1111 1111

()

1024

511

2

REF

V

::

00 0000 0001

()

1024

1

2

REF

V

00 0000 0000

0V

POWER ON RESET

An internal power-on-reset circuit resets the DAC register to all 0s on power-up.

BUFFER AMPLIFIER

The output buffer has a near rail-to-rail output with short circuit protection and can reliably drive a

2k

Ω load with a 100pF load capacitance.

PROGRAMMABLE REFERENCE

The DAC reference can be sourced internally or externally under software control. If an external

reference voltage is applied to the REF pin, the device must be configured to accept this. If an

internal reference is selected, a voltage of 1.024V or 2.048 is available. The internal reference can

source up to 1mA and can therefore be used as an external system reference.