Production Data
WM2639
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
DATA DESTINATION
(PIN 15)
DAC holding latch
Control register
0
1
D11
D10
D9
X
D8
X
D7
X
D6
X
D5
X
D4
D3
D2
X
D1
D0
X
X
REF1 REF0
PWR SPD
Table 1 Register Bits
PROGRAMMABLE SETTLING TIME
Settling time is a software selectable 3.5ms or 1ms, 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 1ms, a ZERO (default) defines a
settling time of 3.5ms.
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 10MW 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
External (default)
1.024V
0
0
1
1
0
1
0
1
2.048V
External
Table 2 Programmable Internal Reference
WOLFSON MICROELECTRONICS LTD
Production Data Rev 1.0 July 1999
9
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
