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WM8706 Schematic ( PDF Datasheet ) - Wolfson Microelectronics plc

Teilenummer WM8706
Beschreibung 24-bit/ 192kHz Stereo DAC with Volume Control
Hersteller Wolfson Microelectronics plc
Logo Wolfson Microelectronics plc Logo 




Gesamt 24 Seiten
WM8706 Datasheet, Funktion
WM8706
24-bit, 192kHz Stereo DAC with Volume Control
Product Preview, Rev 1.2, April 2001
DESCRIPTION
The WM8706 is a high performance stereo DAC designed
for audio applications such as DVD, home theatre systems,
and digital TV. The WM8706 supports data input word
lengths from 16 to 32-bits and sampling rates up to 192kHz.
The WM8706 can implement 2 channels at 192kHz for high-
end DVD-Audio. The WM8706 consists of a serial interface
port, digital interpolation filters, multi-bit sigma delta
modulators and stereo DAC in a small 28-pin SSOP
package. The WM8706 also includes a digitally controllable
mute and attenuate function on each channel.
The WM8706 supports a variety of connection schemes for
audio DAC control. The MPU serial port provides access to
a wide range of features including on-chip mute, attenuation
and phase reversal. A hardware controllable interface is
also available. It is pin-compatible with the WM8716
provided the oscillator circuit on WM8716 is not required in
the application.
The WM8706 is an ideal device to interface to AC-3,
DTS, and MPEG audio decoders for surround sound
applications, or for use in DVD players supporting DVD-A.
BLOCK DIAGRAM
FEATURES
Stereo DAC
Audio Performance
- 106dB SNR (‘A’ weighted @ 48kHz) DAC
- -97dB THD
DAC Sampling Frequency: 8kHz – 192kHz
3-Wire Serial Control Interface or Hardware Control
Programmable Audio Data Interface Modes
- I2S, Left, Right Justified, DSP
- 16/20/24/32 bit Word Lengths
Independent Digital Volume Control on Each Channel with
127.5dB Range in 0.5dB Steps
3.0V – 5.5V Supply Operation
28-Pin SSOP Package
Exceeds Dolby Class A Performance Requirements
APPLICATIONS
DVD-Audio and DVD ‘Universal’ Players
Home theatre systems
Digital TV
Digital broadcast receivers
MODE MLIIS MCDM1 MDDM0 MUTEB CSBIWO ZERO
CONTROL INTERFACE
WM8706
BCKIN
LRCIN
DIN
SERIAL
INTERFACE
MUTE/
ATTEN
MUTE/
ATTEN
DIGITAL FILTERS
SIGMA
DELTA
MODULATOR
SIGMA
DELTA
MODULATOR
RIGHT
DAC
LEFT
DAC
LOW
PASS
FILTER
LOW
PASS
FILTER
VOUTR
VOUTL
VMID
XTI AVDD DVDD
VREFP VREFN AGND DGND
WOLFSON MICROELECTRONICS LTD
Lutton Court, Bernard Terrace, Edinburgh, EH8 9NX, UK
Tel: +44 (0) 131 667 9386
Fax: +44 (0) 131 667 5176
www.wolfsonmicro.com
Product Preview data sheets contain
specifications for products in the formative
phase of development. These products may
be changed or discontinued without notice.
2001 Wolfson Microelectronics Ltd.






WM8706 Datasheet, Funktion
WM8706
Product Preview
Test Conditions
AVDD, DVDD = 5V, AGND, DGND = 0V, TA = +25oC, fs = 48kHz, XTI = 256fs unless otherwise stated.
PARAMETER
SYMBOL TEST CONDITIONS
MIN
TYP
Analogue Output Levels
Output level
Load = 10k ohms,
0dBFS
1.1
Load = 10k ohms,
0dBFS,
(AVDD = 3.3V)
0.726
Gain mismatch
channel-to-channel
±1
Minimum resistance load
To midrail or a.c.
coupled
1
To midrail or a.c.
coupled
600
(AVDD = 3.3V)
Maximum capacitance load
5V or 3.3V
100
Output d.c. level
(VREFP -
VREFN)/2
Power On Reset (POR)
POR threshold
2.4
MAX
UNIT
VRMS
VRMS
%FSR
kohms
ohms
pF
V
V
Notes:
1. Ratio of output level with 1kHz full scale input, to the output level with all zeros into the digital input, measured ‘A’ weighted
over a 20Hz to 20kHz bandwidth.
2. All performance measurements done with 20kHz low pass filter, and where noted an A-weight filter. Failure to use such a
filter will result in higher THD+N and lower SNR and Dynamic Range readings than are found in the Electrical
Characteristics. The low pass filter removes out of band noise; although it is not audible it may affect dynamic specification
values.
3. VMID decoupled with 10uF and 0.1uF capacitors (smaller values may result in reduced performance).
TERMINOLOGY
1. Signal-to-noise ratio (dB) - SNR is a measure of the difference in level between the full scale output and the output with no
signal applied. (No Auto-zero or Automute function is employed in achieving these results).
2. Dynamic range (dB) - DNR is a measure of the difference between the highest and lowest portions of a signal. Normally a
THD+N measurement at 60dB below full scale. The measured signal is then corrected by adding the 60dB to it. (e.g.
THD+N @ -60dB= -32dB, DR= 92dB).
3. THD+N (dB) - THD+N is a ratio, of the rms values, of (Noise + Distortion)/Signal.
4. Stop band attenuation (dB) - Is the degree to which the frequency spectrum is attenuated (outside audio band).
5. Channel Separation (dB) - Also known as Cross-Talk. This is a measure of the amount one channel is isolated from the
other. Normally measured by sending a full scale signal down one channel and measuring the other.
WOLFSON MICROELECTRONICS LTD
PP Rev 1.2 April 2001
6

6 Page









WM8706 pdf, datenblatt
WM8706
Product Preview
AUDIO DATA SAMPLING RATES
The master clock for WM8706 supports audio sampling rates from 128fs to 768fs, where fs is
the audio sampling frequency (LRCIN) typically 32kHz, 44.1kHz, 48kHz, 96kHz or 192kHz. The
master clock is used to operate the digital filters and the noise shaping circuits.
The WM8706 has a master clock detection circuit that automatically determines the relation
between the master clock frequency and the sampling rate (to within +/- 32 master clocks). If
there is a greater than 8 clocks error, the interface shuts down the DAC and mutes the output.
The master clock should be synchronised with LRCIN, although the WM8706 is tolerant of
phase differences or jitter on this clock.
SAMPLING
RATE
(LRCIN)
128fs
MASTER CLOCK FREQUENCY (MHZ) (XTI)
192fs
256fs
384fs
512fs
32kHz
44.1kHz
48kHz
4.096
5.6448
6.114
6.144
8.467
9.216
8.192
11.2896
12.288
12.288
16.9340
18.432
16.384
22.5792
24.576
96kHz
12.288
18.432
24.576
36.864 Unavailable
192kHz
24.576
36.864 Unavailable Unavailable Unavailable
Table 1 Typical Relationships Between System Frequency and Sampling Rates.
768fs
24.576
33.8688
36.864
Unavailable
Unavailable
HARDWARE CONTROL MODES
When the MODE pin is held low, the following hardware modes of operation are available.
MUTE AND AUTOMUTE OPERATION
In both hardware and software modes, pin 25 (MUTEB) controls selection of MUTE directly, and
can be used to enable and disable the automute function, or as an output of the automuted signal.
MUTEB PIN
DESCRIPTION
0 Mute DAC channels
1 Normal Operation
Floating
Enable IZD, MUTEB becomes an output to indicate when IZD occurs.
Table 2 Mute and Automute Control
Figure 9 shows the application and release of MUTE whilst a full amplitude sinusoid is being
played at 48kHz sampling rate. When MUTE (lower trace) is asserted, the output (upper trace)
begins to decay exponentially from the DC level of the last input sample. The output will decay
towards VMID with a time constant of approximately 64 input samples. When MUTE is de-
asserted, the output will restart almost immediately from the current input sample.
WOLFSON MICROELECTRONICS LTD
PP Rev 1.2 April 2001
12

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