WM8753 Wolfson Microelectronics plc, WM8753 Datasheet - Page 72

• Manufacturer Part Number: WM8753
• Description: HI FI AND TELEPHONY DUAL CODEC
• Manufacturer: Wolfson Microelectronics plc

Advanced Information
Figure 27 Bias Current Control
w
MICBIASBST[1:0]
00=x1
01=x2
10=x3
11=x4
adc pga
& zc
IPBIASX0P5
0=x1
1=x0.5
2
adc pga
micpreamp
micpreamp
& zc
mixinv
MBIASBOOST
0=x1
1=x1.5
adc
Table 70 ADC and DAC Oversampling Rate Selection
mixinv
adc
local biasgen
masterbias
line
mix
SAVING POWER BY REDUCING OVERSAMPLING RATE
The default mode of operation of the ADC and DAC digital filters is in 64x oversampling mode. Under
the control of ADCOSR and DACOSR the oversampling rate may be doubled. 64x oversampling
results in a slight decrease in noise performance compared to 128x but lowers the power
consumption of the device. ADC 64x mode is not available in USB mode (USB = 1). In USB mode
ADCOSR must be set to ‘0’.
SAVING POWER BY REDUCING BIAS CURRENTS
There are various biasing options within the WM8753L for increasing or reducing the bias current that
is used by sections of the chip.
VDACBIASX0P5,
DMBIASX0P5 as shown in Figure 27. The performance of the chip may vary when the bias currents
are changed from the default.
mix
R7 (07h)
Sample Rate
Control (2)
rx
R18 (12h)
Additional
Control
REGISTER
ADDRESS
detect
mic
REGISTER
ADDRESS
DMBIASX0P5
0=x1
1=x0.5
mix
alc
mixl
7:6
BIT
mixr
clkdet
clkdet
MICBIASBST,
2
1
0
local biasgen
mixm
VSEL
[1:0]
dac
LABEL
BIT
dacinv
dac
11
VXDACOSR
ADCOSR
DACOSR
DEFAULT
voice
dac
The control of these is via the register bits MBIASBOOST,
BUFBIAS,
dacinv
LABEL
VDACBIASX0P5
0=x1
1=x0.5
dacinv
Analogue Bias optimization
00: Lowest bias current, optimized for AVDD=1.8V
01: Low bias current, optimized for AVDD=2.5V
1X: Default bias current, optimized for AVDD=3.3V
rec mix
IPBIASX0P5,
OPBIASX0P5
0=x1
1=x0.5
1
1
1
spkr pga
DEFAULT
& zc
spkr pga
& zc
BUFBIAS[1:0]
00=x1
01=x0.25
10=x0.5
11=x1.5
local biasgen
hp pga &
zc
ADCBIAS,
DESCRIPTION
Voice DAC oversample rate
select
1 = 64x (lowest power)
0 = 128x (best SNR)
ADC oversample rate select
1 = 64x (lowest power)
0 = 128x (best SNR)
DAC oversample rate select
1 = 64x (lowest power)
0 = 128x (best SNR)
2
hp pga &
buffer
buffer
zc
s/h
s/h
DESCRIPTION
pga & zc
mono
AI Rev 3.1 June 2004
OPBIASX0P5
ADCBIAS[1:0]
00=x1
01=x0.25
10=x0.5
11=x1.5
out3
WM8753L
2
out4
adc
adc
mono
2
and
72