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WM2626ID

Low Power Dual 8-bit Serial Input DAC with Internal Reference

Wolfson Microelectronics plc 

WM2626

Production Data

SOFTWARE CONFIGURATION OPTIONS

Table 2 shows the composition of a 16-bit data word. D11-D4 contains the 8-bit data word, and

D14-D13 hold the programmable options. Bits D15 and D12 are used for addressing the different

latches. D3 to D0 are unused and should be set to ZERO.

D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

R1 SPD PWR R0

New DAC value (8 bits)

0 000

Table 2 Register Map

PROGRAMMABLE CONVERTER SPEED

SPD (Bit 14) allows for software control of the converter speed. A ONE selects the fast mode,

where typical settling time to within ±0.5LSB of the final value is 0.8µs. a ZERO puts the device into

the slow mode, where typical settling time is 2.8µs.

PROGRAMMABLE POWER DOWN

The power down function is controlled by PWR (Bit 13). 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

Data received on the serial interface is routed according to the values of bits R1 and R0, as shown

in Table 3.

R1

R0

(BIT D15)

(BIT D12)

0

0

0

1

1

0

1

1

Table 3 Latch Addressing

REGISTER

Write data to DAC B and buffer

Write data to buffer

Write data to DAC A and update DAC B with buffer content

Write data to control register

To update both DACs simultaneously, the data intended for DAC B should first be stored in the

buffer. Subsequently, writing data to DAC A will automatically update the DAC B latch from the

buffer, so that the analogue output of both DACs will change at the same time.

When updating the two channels independently, all data written to the DAC B latch (R1 and R0 set

to ZERO) is also copied to the buffer. Thus the automatic update of DAC B when writing to DAC A

latch (R1=1, R0=0) does not change the DAC B data. Data should not be written only to the buffer

when operating in this mode.

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 x x x x x x REF1 REF0

Table 4 Control Register Contents

PROGRAMMABLE INTERNAL OR EXTERNAL REFERENCE

The reference can be sourced internally or externally under software control, as detailed in Table 5.

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

this. This will activate the reference input buffer, whose input resistance of 10MΩ (typical) makes

the reference input resistance independent of code.

REF1

REF0

FUNCTION

0

0

Use external reference

0

1

Use internal 1.024V reference

1

0

Use internal 2.048V reference

1

1

Use external reference

Table 5 Programmable Internal Reference

When using the on-chip reference, voltages of 1.024V or 2.048V are available. The internal

reference can source up to 1mA on the REF pin and can therefore be used as a system reference

for external components.

WOLFSON MICROELECTRONICS LTD

PD Rev 1.0 April 2001

8

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