Production Data

WM2639

WOLFSON MICROELECTRONICS LTD

Production Data Rev 1.0 July 1999

9

SOFTWARE CONFIGURATION OPTIONS

DATA FORMAT

The WM2639 writes data either to the DAC holding latch or to the control register depending on the state

of input pin REG.

REG

(PIN 15)

DATA DESTINATION

0

DAC holding latch

1

Control register

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

X

X

X

X

X

X

X

REF1

REF0

X

PWR

SPD

Table 1 Register Bits

PROGRAMMABLE SETTLING TIME

Settling time is a software selectable 3.5

µs or 1µs, typical to within ±0.5LSB of final value. This is

controlled by the value of SPD – Bit D0. A ONE defines a settling time of 1

µs, a ZERO (default) defines a

settling time of 3.5

µs.

PROGRAMMABLE POWER DOWN

The power down function can be controlled by PWR. A ZERO configures the device as active, or fully

powered up, a ONE configures the device into power down mode. When the power down function is

released the device reverts to the DAC code set prior to power down.

PROGRAMMABLE INTERNAL REFERENCE

The 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 external reference is selected, the reference voltage input is buffered which makes the DAC input

resistance independent of code. The REF pin has an input resistance of 10M

Ω and an input capacitance

of typically 55pF. The reference voltage determines the DAC full-scale output.

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.

REF1

REF0

REFERENCE

0

0

External (default)

0

1

1.024V

1

0

2.048V

1

1

External

Table 2 Programmable Internal Reference