WM2636

Production Data

WOLFSON MICROELECTRONICS LTD

PD Rev 1.0 July 1999

8

SOFTWARE CONFIGURATION OPTIONS

The 16 bits of data can be transferred with the sequence shown in Table 2. D11-D0 contains

the 12-bit data word. D15-D12 hold the programmable options.

D15

D14

D13

D12

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

R1

SPD PWR

R0

New DAC or control register value (12 bits)

Table 2 Serial Word Format

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 D14. A ONE defines a settling time of 1

µs, a ZERO defines a

settling time of 3.5

µs.

PROGRAMMABLE POWER DOWN

The power down function is controlled by D13. 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.

REGISTER ADDRESSING

A separate internal control register is available. This is accessed from the register access bits

R1 (Bit D15) and R0 (Bit D12).

R1

(BIT D15)

R0

(BIT D12)

REGISTER

00

Write data to DAC

01

Reserved

10

Reserved

11

Write data to control register

Table 3 Register Access Control

The contents of the control register, shown below in Table 4, are used to program the internal

reference function.

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

x

x

X

x

xx

xx

x

X

REF1 REF0

Table 4 Control Register Contents

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)

REGISTER

00

External

01

1.024V

10

2.048V

11

External

Table 5 Programmable Internal Reference