WM8216

Production Data

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PD Rev 4.0 March 2007

19

REFERENCES

The ADC reference voltages are derived from an internal band-gap reference, and buffered to pins

VRT and VRB, where they must be decoupled to ground. Pin VRX is driven by a similar buffer, and

also requires decoupling. The output buffer from the RLCDAC also requires decoupling at pin

VRLC/VBIAS.

The ADC references can be switched from the default values (VRT=2.05V, VRB=1.05V, ADC input

range=2V) to give a smaller ADC reference range (VRT=1.85V, VRB=1.25V, ADC input range=1.2V)

under control of the LOWREFS register bit. Setting LOWREFS=1 allows smaller input signals to be

accommodated.

Note:

When LOWREFS = 1 the output of the RLCDAC will scale if RLCDACRNG = 1. The max output

from RLCDAC will change from 2.05 to 1.85V and the step size will proportionally reduce.

POWER MANAGEMENT

Power management for the device is performed via the Control Interface. By default the device is

fully enabled. The EN bit allows the device to be fully powered down when set low. Individual blocks

can be powered down using the bits in Setup Register 5. When in MONO mode the unused input

channels are automatically disabled to reduce power consumption.

CONTROL INTERFACE

The internal control registers are programmable via the serial digital control interface. The register

contents can be read back via the serial interface on pin OP[9]/SDO.

It is recommended that a software reset is carried out after the power-up sequence, before writing to

any other register. This ensures that all registers are set to their default values (as shown in Table

5).

SERIAL INTERFACE: REGISTER WRITE

Figure 15 shows register writing in serial mode. Three pins, SCK, SDI and SEN are used. A six-bit

address (a5, 0, a3, a2, a1, a0) is clocked in through SDI, MSB first, followed by an eight-bit data

word (b7, b6, b5, b4, b3, b2, b1, b0), also MSB first. Setting address bit a4 to 0 indicates that the

operation is a register write. Each bit is latched on the rising edge of SCK. When the data has been

shifted into the device, a pulse is applied to SEN to transfer the data to the appropriate internal

register.

SCK

SEN

SDI

a5

0

a3a2a1

a0b7b6b5

b4b3b2b1b0

Address

Data Word

Figure 15 Serial Interface Register Write

A software reset is carried out by writing to Address “000100” with any value of data, (i.e. Data Word

= XXXXXXXX).