Datasheet WM8738 Datasheet (wolfson)

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24 Bit Stereo ADC

WM8738

DESCRIPTION

The WM8738 is a high performance stereo audio ADC designed for consumer applications.

Stereo line-level audio inputs are provided, along with a control input pin to allow operation of the audio interface in either one of two industry standard modes. The device also has a selectable digital high pass filter to remove residual DC offsets.

Stereo 24-bit multi-bit sigma delta ADCs are provided, along with oversampling digital interpolation filters. 24-bit digital audio output word lengths and sampling rates from 32kHz to 96kHz are supported.

The device is available in a small 14-pin SOIC package.

BLOCK DIAGRAM

FEATURES

• Audio Performance

- 90 dB SNR (‘A’ weighted @ 48kHz)

• 3.0 – 5.5V Analogue Supply Operation

• 3.0 – 3.6V Digital Supply Operation

• ADC Sampling Frequency: 32kHz – 96kHz

• Selectable ADC High Pass Filter

• Selectable Audio Data Interface Modes

• 14-pin SOIC Package

- I

S or Left Justified

APPLICATIONS

• CD and Minidisc Recorders

• DVD Players

• General Purpose Audio Conversion

WOLFSON MICROELECTRONICS plc

www.wolfsonmicro.com

Production Data, November 2004, Rev 4.3

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WM8738 Production Data

TABLE OF CONTENTS

DESCRIPTION .......................................................................................................1

FEATURES.............................................................................................................1

APPLICATIONS .....................................................................................................1

BLOCK DIAGRAM .................................................................................................1

TABLE OF CONTENTS .........................................................................................2

PIN CONFIGURATION...........................................................................................3

ORDERING INFORMATION ..................................................................................3

PIN DESCRIPTION ................................................................................................4

ABSOLUTE MAXIMUM RATINGS.........................................................................5

RECOMMENDED OPERATING CONDITIONS .....................................................5

ELECTRICAL CHARACTERISTICS ......................................................................6

TERMINOLOGY .....................................................................................................7

DIGITAL AUDIO INTERFACE TIMING ..................................................................8

DEVICE DESCRIPTION .........................................................................................9

INTRODUCTION........................................................................................................... 9

ADC............................................................................................................................... 9

ADC DIGITAL FILTER................................................................................................... 9

AUDIO DATA SAMPLING RATES............................................................................... 10

DIGITAL AUDIO INTERFACES................................................................................... 11

DIGITAL FILTER CHARACTERISTICS ...............................................................12

ADC FILTER RESPONSES .................................................................................12

ADC HIGH PASS FILTER ........................................................................................... 12

APPLICATIONS INFORMATION .........................................................................13

RECOMMENDED EXTERNAL COMPONENTS.......................................................... 13

RECOMMENDED EXTERNAL COMPONENTS VALUES........................................... 13

PACKAGE DIMENSIONS ....................................................................................14

IMPORTANT NOTICE ..........................................................................................15

ADDRESS: .................................................................................................................. 15

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WM8738 Production Data

PIN CONFIGURATION

DVDD

SDATO

BCLK

FMT

CAP

VREF

RIN

WM8738

ORDERING INFORMATION

DEVICE

WM8738ED -25 to +85oC

WM8738ED/R -25 to +85oC

WM8738GED/V -25 to +85oC

TEMPERATURE

RANGE

DGND

MCLK

LRCLK

NOHP

AGND

AVDD

LIN

MOISTURE SENSITIVITY

PACKAGE

14-pin SOIC MSL 1

14-pin SOIC

(tape and reel)

14-pin SOIC

(lead free)

LEVEL

MSL 1

MSL 2

PEAK SOLDERING

TEMPERATURE

240°C

260°C

WM8738GED/RV -25 to +85oC

Note:

Reel quantity = 3,000

14-pin SOIC

(lead free, tape and reel)

MSL 2

260°C

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WM8738 Production Data

PIN DESCRIPTION

PIN NAME TYPE DESCRIPTION

1 DVDD Supply

2 SDATO Digital Output

3 BCLK Digital Input

4 FMT Digital input (with pull down)

5 CAP Analog

6 VREF Analogue output

7 RIN Analogue Input

8 LIN Analogue Input

9 AVDD Supply

10 AGND Supply

11 NOHP Digital input (with pull down)

12 LRCLK Digital Input

13 MCLK Digital Input

14 DGND Supply

Notes

1. Digital input pins have Schmitt trigger input buffers and are 5V tolerant.

Digital positive supply

ADC digital data output

ADC audio interface data clock (5V tolerant)

Audio interface format selection (5V tolerant)

‘0’ = I

‘1’ = Left Justified

Reference de-coupling pin

Buffered reference decoupling pin

Right channel ADC input

Left channel ADC input

Analogue positive supply

Analogue ground supply and chip substrate

Digital highpass filter bypass; (5V tolerant)

‘0’ = Enabled

‘1’ = Bypassed

Data left/right word clock (5V tolerant)

Master clock input (5V tolerant)

Digital supply ground

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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

Wolfson tests its package types according to IPC/JEDEC J-STD-020B for Moisture Sensitivity to determine acceptable storage conditions prior to surface mount assembly. These levels are:

MSL1 = unlimited floor life at <30°C / 85% Relative Humidity. Not normally stored in moisture barrier bag. MSL2 = out of bag storage for 1 year at <30°C / 60% Relative Humidity. Supplied in moisture barrier bag. MSL3 = out of bag storage for 168 hours at <30°C / 60% Relative Humidity. Supplied in moisture barrier bag.

CONDITION

Digital supply voltage

Analogue supply voltage

Voltage range digital inputs

Voltage range analogue inputs

Master Clock Frequency

Operating temperature range, TA

Storage temperature prior to soldering

Storage temperature after soldering

Notes

1. Analogue and digital grounds must always be within 0.3V of each other.

2. The digital supply voltage must always be less than or equal to the analogue supply voltage.

of this device.

MIN MAX

-0.3V +4.2V

-0.3V +7.0V

DGND -0.3V +7.0V

AGND -0.3V AVDD +0.3V

37MHz

-25°C +85°C 30°C max / 85% RH max

-65°C +150°C

RECOMMENDED OPERATING CONDITIONS

PARAMETER SYMBOL TEST

Digital supply range

Analogue supply range

Ground

Analogue supply current

Supply Current Low Power Mode

Digital supply current

DVDD 3.0 3.6 V

AVDD 3.0 5.5 V

DGND,AGND 0

AVDD = 5.0V,

AVDD = 3.3V,

AVDD = 5.0V

AVDD = 3.3V

DVDD = 3.3V

CONDITIONS

(DVDD at 3.3V)

AVDD = 5.0V or 3.3V

MIN TYP MAX UNIT

180

110

PD Rev 4.3 November 2004

µA

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WM8738 Production Data

ELECTRICAL CHARACTERISTICS

Test Conditions

AVDD = 5.0V, AGND = 0V, DVDD = 3.3V, DGND = 0V, T

PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT

Digital Logic Levels (TTL Levels)

Input LOW level VIL

Input HIGH level VIH

Output LOW VOL

Output HIGH VOH

Pull down resistance (FMT,

RPD

NOHP)

Analogue Reference Levels

Reference voltage V

Buffered reference voltage V

Potential divider output

CAP

REF

CAP

impedance

Input to ADC

Input Signal Level (0dB) V

RIN / VLIN

SNR (Note 1,2)

Dynamic Range (Note 2) DNR

Total Harmonic Distortion (THD)

(Note 4)

ADC channel separation

Power Supply Rejection Ratio

PSRR

Input Resistance 20 kΩ

Input Capacitance

Notes

1. Ratio of output level with 1kHz full scale input, to the output level with the input open circuited, measured ‘A’ weighted over a 20Hz to 20kHz bandwidth using an Audio analyser.

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. VREF and CAP de-coupled with 10uF and 0.1uF capacitors (smaller values may result in reduced performance).

4. This data is measured, using an active filter on the device inputs.

= +25oC, fs = 48kHz, MCLK = 256fs unless otherwise stated.

0.8 V

2.0 V

= 1mA 0.1 x DVDD V

= 1mA 0.9 x DVDD V

100 kΩ

AVDD/2 –

50mV

AVDD/2 AVDD/2 +

50mV

CAP

40 50 60 kΩ

1.0 Vrms

A-weighted, 0dB gain

90 dB

@ fs = 48KHz

A-weighted, 0dB gain

90 dB

@ fs = 96KHz

A-weighted, 0dB gain

90 dB

fs = 48KHz, AVDD =

3.3V

A-weighted, -60dB full

90 97 dB

scale input

-1dB input, 0dB gain -87 dB

1KHz input 95 dB

1kHz 100mV

20Hz to 20kHz

100mV

50 dB

p-p

45 dB

p-p

10 pF

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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 r.m.s. 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.

6. Pass-Band Ripple - Any variation of the frequency response in the pass-band region.

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WM8738 Production Data

DIGITAL AUDIO INTERFACE TIMING

MCL K L

MCLK

MCL KH

MCL KY

Figure 1 Master Clock Timing Requirements

Test Conditions

AVDD = 5.0V, AGND = 0V, DVDD = 3.3V, DGND = 0V, T

PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT

System Clock Timing Information

MCLK System clock pulse width high

MCLK System clock pulse width low

MCLK System clock cycle time

MCLKH

MCLKL

MCLKY

BCH

= +25oC, fs = 48kHz, MCLK = 256fs unless otherwise stated.

10 ns

27 ns

BCL

BCLK

LRCLK

SDATO

BCY

LRH

LRS U

Figure 2 Digital Audio Data Timing

Test Conditions

AVDD = 5.0V, AGND = 0V, DVDD = 3.3V, DGND = 0V, T

PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT

Audio Data Input Timing Information

BCLK cycle time

BCLK pulse width high

BCLK pulse width low

LRCLK set-up time to BCLK

BCY

BCH

BCL

LRSU

rising edge

LRCLK hold time from

LRH

BCLK rising edge

SDATO propagation delay

from BCLK falling edge

= +25oC, fs = 48kHz, MCLK = 256fs unless otherwise stated.

80 ns

40 ns

10 ns

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WM8738 Production Data

DEVICE DESCRIPTION

INTRODUCTION

The WM8738 is an ADC designed for audio recording. It’s features, performance and low power consumption make it ideal for recordable CD or DVD players, karaoke, MP3 players and mini-disc players.

The on-board stereo analogue to digital converter (ADC) is of a high quality using a multi-bit highorder oversampling architecture delivering optimum performance with low power consumption. The ADC includes a selectable digital high pass filter to remove unwanted DC components from the audio signal. The device supports system clock inputs of 256, 384, 512fs or 768fs (fs is the sampling rate)

The output from the ADC is available on the digital audio interface in either I data formats.

S or left justified audio

ADC

The line inputs are biased internally through the operational amplifier to V

The WM8738 uses a multi-bit over sampled sigma-delta ADC. A single channel of the ADC is illustrated in Figure 3.

LIN/RIN

Figure 3 Multi-Bit Oversampling Sigma Delta ADC Schematic

The use of multi-bit feedback and high oversampling rates reduces the effects of jitter and high frequency noise.

The ADC Full Scale input is 1.0V rms at AVDD = 5.0 volts. Any voltage greater than full scale will possibly overload the ADC and cause distortion. Note that the full scale input tracks directly with AVDD.

ANALO G

INTEGRATOR

MULTI

BITS

CAP

TO ADC DIGITAL FILTERS

The ADC filters perform true 24 bit signal processing to convert the raw multi-bit oversampled data from the ADC to the correct sampling frequency to be output on the digital audio interface.

ADC DIGITAL FILTER

The ADC digital filters contain a digital high pass filter, selectable via pin NOHP.

NOHP = 0 Digital high pass filter enabled

NOHP = 1 Digital high pass filter bypassed

The high-pass filter response detailed in Digital Filter Characteristics. The operation of the high pass filter removes residual DC offsets that are present on the audio signal.

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AUDIO DATA SAMPLING RATES

In a typical digital audio system there is only one central clock source producing a reference clock to which all audio data processing is synchronised. This clock is often referred to as the audio system’s Master Clock. The external master system clock can be applied directly through the MCLK input pin. In a system where there are a number of possible sources for the reference clock it is recommended that the clock source with the lowest jitter be used to optimise the performance of the ADC.

The master clock for WM8738 supports audio sampling rates from 256fs to 768fs, where fs is the audio sampling frequency LRCLK, typically 32kHz, 44.1kHz, 48kHz, or 96kHz. The master clock is used to operate the digital filters and the noise shaping circuits.

The WM8738 has a master clock detection circuit that automatically determines the relationship between the master clock frequency and the sampling rate (to within +/- 32 system clocks). If there is a greater than 32 clocks error the interface is disabled and maintains the output level at the last sample. The master clock must be synchronised with LRCLK, although the WM8738 is tolerant of phase variations or jitter on this clock. Table 1 shows the typical master clock frequency inputs for the WM8738.

If MCLK is stopped for greater than 10us then the device will enter a low power mode where the current taken from AVDD is greatly reduced. Note that when the device enters this mode the references are powered down.

Table 1 shows the common MCLK frequencies for different sample rates.

SAMPLING

RATE

(LRCLK)

32kHz 8.192 12.288 16.384 24.576

44.1kHz 11.2896 16.9340 22.5792 33.8688

48kHz 12.288 18.432 24.576 36.864

96kHz 24.576 36.864 Unavailable Unavailable

Table 1 Master Clock Frequency Selection

Master Clock Frequency (MHz)

256fs 384fs 512fs 768fs

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WM8738 Production Data

DIGITAL AUDIO INTERFACES

The WM8738 has two data output formats, selectable via the FMT pin.

FMT = 0 ADC audio data output is I

FMT = 1 ADC audio data output is Left Justified

Both of these modes are MSB first.

The digital audio interface takes the data from the internal ADC digital filter. SDATO is the formatted digital audio data stream output from the ADC digital filters with left and right channels multiplexed together. LRCLK is an alignment clock that controls whether Left or Right channel data is present on the SDATO line. SDATO and LRCLK are synchronous with the BCLK signal with each data bit transition signified by a low to high BCLK transition.

LEFT JUSTIFIED MODE

In left justified mode, the MSB of the ADC data is output on SDATO and changes on the same falling edge of BCLK as LRCLK and may be sampled on the rising edge of BCLK. LRCLK is high during the left samples and low during the right samples.

LRCLK

BCLK

1/fs

LEFT CHANNEL RIGHT CHANNEL

SDATO

n321n-2n-1

LSBMSB

n321n-2n-1

LSBMSB

Figure 4 Left Justified Mode Timing Diagram

S MODE

In I2S mode, the MSB of the ADC data is output on SDATO and changes on the first falling edge of BCLK following an LRCLK transition and may be sampled on the rising edge of BCLK. LRCLK is low during the left samples and high during the right samples.

1/fs

LEFT CHANNEL RIGHT CHANNEL

LRCLK

BCLK

MSB

1 BCLK

n321n-2n-1

LSB

SDATO

Figure 5 I

1 BCLK

MSB

S Mode Timing Diagram

n321n-2n-1

LSB

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WM8738 Production Data

DIGITAL FILTER CHARACTERISTICS

PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT

Passband

Stopband

Passband ripple

Stopband

Stopband Attenuation

Group Delay

±0.01 dB 0 0.4535fs dB

-6dB 0.5fs ±0.01 dB

0.5465fs

f > 0.5465fs -65 dB

22 Samples

Table 2 Digital Filter Characteristics

ADC FILTER RESPONSES

0.02

-20

-40

Response (dB)

-60

-80

0 0.5 1 1.5 2 2.5 3

Frequency (Fs)

0.015

0.01

0.005

Response (dB)

-0.005

-0.01

-0.015

-0.02 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5

Frequency (Fs)

Figure 6 ADC Digital Filter Frequency Response Figure 7 ADC Digital Filter Ripple

ADC HIGH PASS FILTER

The WM8738 has a selectable digital highpass filter to remove DC offsets. The filter response is characterised by the following polynomial.

-1

H(z) =

-5

-10

Response (dB)

-15

0 0.0005 0.001 0.0015 0.002

1 - z

1 - 0.9995z

-1

Frequency (Fs)

Figure 8 ADC Highpass Filter Response

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WM8738 Production Data

APPLICATIONS INFORMATION

RECOMMENDED EXTERNAL COMPONENTS

DVDD

Hardware

Control

DVDD

Audio Serial Data I/F

DVDD

DGND

FMT

AVDD

AGND

LIN

WM8738

NOHP

MCLK

BCLK

LRCLK

SDATO

RIN

VREF

CAP

AVDD

AGND

Notes:

1. AGND and DGND should be connected as close to the WM8738 as possible. , C3, C9 and C

2. C

3. Capacitor types should be carefully chosen. Capacitors with very low ESR are recommended for optimum

should be positioned as close to the WM8738 as possible.

performance.

Figure 9 External Components Diagram

RECOMMENDED EXTERNAL COMPONENTS VALUES

COMPONENT

REFERENCE

C1 and C4 10µF C2 and C3 0.1µF C5 and C7 1µF Analogue input AC coupling caps

C6 and C8 4.7nF R2 and R3 10kΩ R1 and R4 680Ω

C9 0.1µF C10 10µF C11 0.1µF C12 10µF

Table 3 External Components Description

SUGGESTED

VALUE

DESCRIPTION

De-coupling for DVDD and AVDD

Analogue input filtering (RC) capacitor

Current limiting resistors

Analogue input filtering (RC) resistor

Reference de-coupling capacitors for VREF pin

Reference de-coupling capacitors for CAP pin

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WM8738 Production Data

PACKAGE DIMENSIONS

D: 14 PIN SOIC 3.9mm Wide Body

0.10 (0.004)

DM001.C

h x 45

-C-

SEATING PLANE

Symbols

Dimensions

(mm)

Dimensions

(Inches)

MIN MAX MIN MAX

A 1.35 1.75 0.0532 0.0688

A1 0.10 0.25 0.0040 0.0098

0.33 0.51 0.0130 0.0200

C 0.19 0.25 0.0075 0.0098 D E

8.55 8.75 0.3367 0.3444

3.80 4.00 0.1497 0.1574

e 1.27 BSC 0.05 BSC H h L 0.40 1.27 0.0160 0.0500

αααα

REF:

NOTES: A. ALL LINEAR DIMENSIONS ARE IN MILLIMETERS (INCHES). B. THIS DRAWING IS SUBJE CT TO CHANGE WI THOUT NOT ICE. C. BODY DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSION, NOT TO EXCEED 0.25MM (0.010IN). D. MEETS JEDEC.95 MS-012, VARIATION = AB. REFER TO THIS SPECIFICATION FOR FURTHER DETAILS.

5.80 6.20 0.2284 0.2440

0.25 0.50 0.0099 0.0196

JEDEC.95, MS-012

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WM8738 Production Data

IMPORTANT NOTICE

Wolfson Microelectronics plc (W M) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current. All products are sold subject to the WM terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability.

WM warrants performance of its products to the specifications applicable at the time of sale in accordance with W M’s standard warranty. Testing and other quality control techniques are utilised to the extent WM deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements.

In order to minimise risks associated with customer applications, adequate design and operating safeguards must be used by the customer to minimise inherent or procedural hazards. Wolfson products are not authorised for use as critical components in life support devices or systems without the express written approval of an officer of the company. Life support devices or systems are devices or systems that are intended for surgical implant into the body, or support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided, can be reasonably expected to result in a significant injury to the user. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.

WM assumes no liability for applications assistance or customer product design. WM does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of WM covering or relating to any combination, machine, or process in which such products or services might be or are used. WM’s publication of information regarding any third party’s products or services does not constitute WM’s approval, license, warranty or endorsement thereof.

Reproduction of information from the WM web site or datasheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations and notices. Representation or reproduction of this information with alteration voids all warranties provided for an associated WM product or service, is an unfair and deceptive business practice, and WM is not responsible nor liable for any such use.

Resale of WM’s products or services with statements different from or beyond the parameters product or service voids all express and any implied warranties for the associated WM product or service, is an unfair and deceptive business practice, and WM is not responsible nor liable for any such use.

stated by WM for that

ADDRESS:

Wolfson Microelectronics plc

26 Westfield Road

Edinburgh

EH11 2QB

United Kingdom

Tel :: +44 (0)131 272 7000

Fax :: +44 (0)131 272 7001

Email :: [email protected]

PD Rev 4.3 November 2004