WM8216
Production Data
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
a5
0
a3
a2
a1
a0
b7
b6
b5
b4
b3
b2
b1
b0
SDI
Address
Data Word
SEN
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).
PD Rev 4.0 March 2007
19
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
