Document Outline
- WM8726
- DESCRIPTION
- FEATURES
- APPLICATIONS
- BLOCK DIAGRAM
- PIN CONFIGURATION
- ORDERING INFORMATION
- PIN DESCRIPTION
- ABSOLUTE MAXIMUM RATINGS
- DC ELECTRICAL CHARACTERISTICS
- ELECTRICAL CHARACTERISTICS
- TERMINOLOGY
- MASTER CLOCK TIMING
- DIGITAL AUDIO INTERFACE
- DEVICE DESCRIPTION
- GENERAL INTRODUCTION
- DAC CIRCUIT DESCRIPTION
- CLOCKING SCHEMES
- DIGITAL AUDIO INTERFACE
- AUDIO DATA SAMPLING RATES
- HARDWARE CONTROL MODES
- DIGITAL FILTER CHARACTERISTICS
- DAC FILTER RESPONSES
- DIGITAL DE-EMPHASIS CHARACTERISTICS
- RECOMMENDED EXTERNAL COMPONENTS
- RECOMMENDED EXTERNAL COMPONENTS VALUES
- RECOMMENDED ANALOGUE LOW PASS FILTER
- PCB LAYOUT RECOMMENDATIONS
- PACKAGE DRAWING
- IMPORTANT NOTICE
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WM8726
24-bit 192kHz Stereo DAC
WOLFSON MICROELECTRONICS LTD
www.wolfsonmicro.com
Product Preview September 2002, Rev 1.5
Copyright
2002 Wolfson Microelectronics Ltd.
DESCRIPTION
The WM8726 is a high performance stereo DAC designed
for audio applications such as DVD, home theatre systems,
and digital TV. The WM8726 supports data input word
lengths from 16 to 24-bits and sampling rates up to 192kHz.
The WM8726 consists of a serial interface port, digital
interpolation filters, multi-bit sigma delta modulators and
stereo DAC in a 14-pin SOIC package.
The WM8726 has a hardware control interface for selection
of audio data interface format, mute and de-emphasis. The
WM8726 supports I
2
S, right Justified or DSP interfaces.
The WM8726 is an ideal device to interface to AC-3
,
DTS
, and MPEG audio decoders for surround sound
applications, or for use in DVD players, including supporting
the implementation of 2 channels at 192kHz for high-end
DVD-Audio applications.
FEATURES
Stereo
DAC
Audio
Performance
-
100dB SNR (`A' weighted @ 48kHz)
-
-88dB
THD
DAC Sampling Frequency: 8kHz 192kHz
Pin Selectable Audio Data Interface Format
-
I
2
S, 16-bit Right Justified or DSP
2.7V - 5.5V Supply Operation
14-pin SOIC Package
Pin Compatible with WM8725
APPLICATIONS
DVD
Players
Home
Theatre
Systems
Digital
TV
Digital Set Top Boxes
BLOCK DIAGRAM
W
WM8726
BCKIN
AUDIO
INTERFACE
MUTE
CONTROL
INTERFACE
VOUTL
VOUTR
LRCIN
DIN
MUTE
DIGITAL
FILTERS
MCLK
DEEMPH
MUTE
FORMAT
CAP
RIGHT
DAC
LEFT
DAC
GND
VDD
SIGMA
DELTA
MODULATOR
SIGMA
DELTA
MODULATOR
WM8726
Product Preview
w
PP Rev 1.5 September 2002
2
PIN CONFIGURATION
ORDERING INFORMATION
DEVICE TEMP.
RANGE
PACKAGE
WM8726ED
-25 to +85
o
C 14-pin
SOIC
10
9
8
14
13
12
11
WM8726
5
6
7
1
2
3
4
VDD
VOUTL
MUTE
NC
DEEMPH
MCLK
FORMAT
GND
VOUTR
CAP
NC
BCKIN
LRCIN
DIN
PIN DESCRIPTION
PIN NAME
TYPE
DESCRIPTION
1
LRCIN
Digital input
Sample rate clock input
2
DIN
Digital input
Serial audio data input
3
BCKIN
Digital input
Bit clock input
4
NC
No connect
No internal connection
5
CAP
Analogue output
Analogue internal reference
6
VOUTR
Analogue output
Right channel DAC output
7
GND Supply
Negative
supply
8
VDD Supply
Positive
supply
9
VOUTL
Analogue output
Left channel DAC output
10
MUTE
Digital input
Soft mute control, Internal pull down
High Impedance = Automute
High = Mute ON
Low = Mute OFF
11
NC
No connect
No internal connection
12
DEEMPH
Digital input
De-emphasis select, Internal pull up
High = de-emphasis ON
Low = de-emphasis OFF
13
FORMAT
Digital input
Data input format select, Internal pull up
Low = 16-bit right justified or DSP `late'
High = 16-24-bit I
2
S or DSP `early'
14
MCLK
Digital input
Master clock input
Note:
1.
Digital input pins have Schmitt trigger input buffers.
WM8726
Product Preview
w
PP Rev 1.5 September 2002
3
ABSOLUTE MAXIMUM RATINGS
Absolute Maximum Ratings are stress ratings only. Permanent damage to the device may be caused by continuously operating at
or beyond these limits. Device functional operating limits and guaranteed performance specifications are given under Electrical
Characteristics at the test conditions specified.
ESD Sensitive Device. This device is manufactured on a CMOS process. It is therefore generically susceptible
to damage from excessive static voltages. Proper ESD precautions must be taken during handling and storage
of this device.
CONDITION
MIN MAX
Supply voltage
-0.3V +7V
Voltage range digital inputs
GND -0.3V
VDD +0.3V
Master Clock Frequency
50MHz
Operating temperature range, T
A
-25
C +85
C
Storage temperature prior to soldering
30
C max / 85% RH max
Storage temperature after soldering
-65
C +150
C
Package body temperature (soldering 10 seconds)
+240
C
Package body temperature (soldering 2 minutes)
+183
C
WM8726
Product Preview
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PP Rev 1.5 September 2002
4
DC ELECTRICAL CHARACTERISTICS
PARAMETER SYMBOL
TEST
CONDITIONS
MIN
TYP
MAX
UNIT
Supply range
VDD
2.7
5.5
V
Ground
GND
0
V
Supply current
VDD
=
5V
27
mA
Supply current
VDD = 3.3V
23
mA
Power down current (note 4)
VDD=3.3V 0.5 mA
ELECTRICAL CHARACTERISTICS
Test Conditions
VDD = 5V, GND = 0V, T
A
= +25
o
C, fs = 48kHz, MCLK = 256fs unless otherwise stated.
PARAMETER SYMBOL
TEST
CONDITIONS
MIN
TYP
MAX
UNIT
Digital Logic Levels (TTL Levels)
Input LOW level
V
IL
0.8
V
Input HIGH level
V
IH
2.0
V
Output LOW
V
OL
I
OL
= 2mA
GND + 0.3V
V
Output HIGH
V
OH
I
OH
= 2mA
VDD - 0.3V
V
Analogue Reference Levels
Reference voltage (CAP)
VDD/2
V
Potential divider resistance
R
CAP
VDD to CAP and CAP
to GND
50k
Ohms
DAC Output (Load
= 10k ohms. 50pF)
0dBFs Full scale output voltage
At DAC outputs
1.1 x
VDD/5
V
rms
SNR (Note 1,2,3)
A-weighted,
@ fs = 48kHz
94 100 dB
SNR (Note 1,2,3)
A-weighted
@ fs = 96kHz
97 dB
SNR (Note 1,2,3)
A-weighted
@ fs = 192kHz
97 dB
SNR (Note 1,2,3)
A-weighted,
@ fs = 48kHz
VDD = 3.3V
95 dB
SNR (Note 1,2,3)
A-weighted
@ fs = 96kHz
VDD = 3.3V
95 dB
SNR (Note 1,2,3)
Non `A' weighted @ fs
= 48kHz
98 dB
THD (Note 3)
1kHz,
0dBFs -88 dB
Dynamic Range (Note 2)
1kHz, THD+N @
-60dBFs
90 100 dB
DAC channel separation
93
dB
WM8726
Product Preview
w
PP Rev 1.5 September 2002
5
Test Conditions
VDD = 5V, GND = 0V, T
A
= +25
o
C, fs = 48kHz, MCLK = 256fs unless otherwise stated.
PARAMETER SYMBOL
TEST
CONDITIONS
MIN
TYP
MAX
UNIT
Analogue Output Levels
Load = 10k ohms,
0dBFS
1.1 V
RMS
Output level
Load = 10k ohms,
0dBFS,
(VDD = 3.3V)
0.72 V
RMS
Gain mismatch
channel-to-channel
1
%FSR
To midrail or a.c.
coupled
1
kOhms
Minimum resistance load
To midrail or a.c.
coupled
(VDD = 3.3V)
1
kOhms
Maximum capacitance load
5V or 3.3V
100
pF
Output d.c. level
VDD/2
V
Power On Reset (POR)
POR threshold
1.8
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.
CAP pin decoupled with 10uF and 0.1uF capacitors (smaller values may result in reduced performance).
4.
Power down occurs 1.5
s after MCLK is stopped.
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.
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