WM8726 Wolfson Microelectronics plc, WM8726 Datasheet

Page 1

... The 2 WM8726 supports I 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 ...

Page 2

... WM8726 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 DC ELECTRICAL CHARACTERISTICS .....................................................................6 ELECTRICAL CHARACTERISTICS ...........................................................................6 TERMINOLOGY ................................................................................................................. 7 MASTER CLOCK TIMING...........................................................................................8 DIGITAL AUDIO INTERFACE.....................................................................................8 POWER ON RESET (POR).........................................................................................9 DEVICE DESCRIPTION............................................................................................11 GENERAL INTRODUCTION .............................................................................................11 DAC CIRCUIT DESCRIPTION ..........................................................................................11 CLOCKING SCHEMES .....................................................................................................12 DIGITAL AUDIO INTERFACE ...

Page 3

... WM8726 PIN CONFIGURATION LRCIN 1 DIN 2 BCKIN 3 WM8726 NC 4 CAP 5 VOUTR 6 GND 7 ORDERING INFORMATION TEMPERATURE DEVICE RANGE WM8726GED/V -40 to +85 WM8726GED/RV -40 to +85 Notes: 1. Reel quantity = 3,000 w 14 MCLK 13 FORMAT 12 DEEMPH MUTE 9 VOUTL 8 VDD PACKAGE 14-lead SOIC o C (Pb-free) 14-lead SOIC o C (Pb-free, tape and reel) ...

Page 4

... WM8726 PIN DESCRIPTION PIN NAME 1 LRCIN Digital input DIN Digital input 2 3 BCKIN Digital input connect 5 CAP Analogue output 6 VOUTR Analogue output 7 GND Supply VDD Supply 8 9 VOUTL Analogue output MUTE Digital input connect 12 DEEMPH Digital input 13 FORMAT ...

Page 5

... WM8726 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 therefore generically susceptible to damage from excessive static voltages ...

Page 6

... WM8726 DC ELECTRICAL CHARACTERISTICS PARAMETER Supply range Ground Supply current Supply current Power down current (note 4) ELECTRICAL CHARACTERISTICS All MIN/MAX characteristics are guaranteed over the recommended operating conditions. Typical characteristics are based on measurements taken under the test conditions specified below. Test Conditions ...

Page 7

... WM8726 Test Conditions o VDD = 5V, GND = 0V + 48kHz, MCLK = 256fs unless otherwise stated. A PARAMETER Gain mismatch channel-to-channel Minimum resistance load Maximum capacitance load Output d.c. level Power On Reset (POR) POR threshold 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 ...

Page 8

... WM8726 MASTER CLOCK TIMING MCLK Figure 1 Master Clock Timing Requirements Test Conditions o VDD = 5V, GND = 0V + 48kHz, MCLK = 256fs unless otherwise stated. A PARAMETER System Clock Timing Information MCLK Master clock pulse width high MCLK Master clock pulse width low MCLK Master clock cycle time ...

Page 9

... WM8726 POWER ON RESET (POR) The WM8726 has an internal power-on-reset (POR) circuit which is used to reset the digital logic into a default state after power up. A block diagram of the reset circuit is shown in Figure 3 Figure 3 Block Diagram of Power-On-Reset The active low reset signal NPOR will be asserted low until VDD=2.4V, which means VMID rises to 1 ...

Page 10

... WM8726 Figure 5 illustrates the NPOR generation when the power is removed. Figure 5 Generation of NPOR at Power-Off-Reset w Production Data PD Rev 4.6 May 2008 10 ...

Page 11

... The device is packaged in a small 14-pin SOIC. DAC CIRCUIT DESCRIPTION The WM8726 DAC is designed to allow playback of 24-bit PCM audio or similar data with high resolution and low noise and distortion. Sample rates up to 192kHz may be used, with much lower sample rates acceptable provided that the ratio of sample rate (LRCIN) to master clock (MCLK) is maintained at one of the required rates ...

Page 12

... Master Clock. The external master clock can be applied directly through the MCLK input pin with no configuration necessary for sample rate selection. Note that on the WM8726, MCLK is used to derive clocks for the DAC path. The DAC path consists of DAC sampling clock, DAC digital filter clock and DAC digital audio interface timing 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 DAC ...

Page 13

... Figure 7 Right Justified Mode Timing Diagram DSP MODE A DSP compatible, time division multiplexed format is also supported by the WM8726. This format is of the type where a ‘synch’ pulse is followed by two data words (left and right) of predetermined word length. (16-bits). The ‘synch’ pulse replaces the normal duration LRCIN, and DSP mode is auto-detected by the shorter than normal duration of the LRCIN ...

Page 14

... Figure 9 DSP Mode B Timing AUDIO DATA SAMPLING RATES The master clock for WM8726 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. ...

Page 15

... WM8726 HARDWARE CONTROL MODES The WM8726 is hardware programmable providing the user with options to select input audio data format, de-emphasis and mute. MUTE AND AUTO MUTE OPERATION Pin 10 (MUTE) controls selection of MUTE directly, and can be used to enable and disable the automute function output of the automuted signal. ...

Page 16

... Note 2. For data widths greater than 24 bits, the LSB’s will be truncated and the most significant 24 bits will be used by the internal processing exactly 16 BCKIN cycles occur in both the low and high period of LRCIN the WM8726 will assume the data is 16-bit and accept the data accordingly. INPUT DSP FORMAT SELECTION ...

Page 17

... WM8726 DIGITAL FILTER CHARACTERISTICS PARAMETER Passband Edge Passband Ripple Stopband Attenuation Table 6 Digital Filter Characteristics DAC FILTER RESPONSES 0 -20 -40 -60 -80 -100 -120 0 0.5 1 1.5 Frequency (Fs) Figure 12 DAC Digital Filter Frequency Response -44.1, 48 and 96kHz 0 -20 -40 -60 -80 0 0.2 0.4 Frequency (Fs) Figure 14 DAC Digital Filter Frequency Response -192kHz ...

Page 18

... WM8726 DIGITAL DE-EMPHASIS CHARACTERISTICS - Frequency (kHz) Figure 16 De-Emphasis Frequency Response (32kHz - Frequency (kHz) Figure 18 De-Emphasis Frequency Response (44.1kHz - Frequency (kHz) Figure 20 De-Emphasis Frequency Response (48kHz 0.5 0 -0.5 -1 -1 ...

Page 19

... AGND Hardware Control Audio Serial Data I/F Notes: 1. C2, C5 should be positioned as close to the WM8726 as possible. 2. Capacitor types should be carefully chosen. Capacitors with very low ESR are recommended for optimum performance and C4 not required if using the recommended low pass filter in Figure 20. ...

Page 20

... An external low pass filter is recommended (see Figure 20) if the device is driving a wideband amplifier. In some applications, a passive RC filter may be adequate. PCB LAYOUT RECOMMENDATIONS Care should be taken in the layout of the PCB that the WM8726 mounted to. The following notes will help in this respect: 1. ...

Page 21

... WM8726 PACKAGE DIMENSIONS D: 14 PIN SOIC 3.9mm Wide Body 0.10 (0.004) Dimensions Symbols (mm) MIN A 1.35 A1 0.10 B 0.33 C 0.19 D 8.55 E 3.80 e 1.27 BSC H 5.80 h 0. REF: JEDEC.95, MS-012 NOTES: A. ALL LINEAR DIMENSIONS ARE IN MILLIMETERS (INCHES). B. THIS DRAWING IS SUBJECT TO CHANGE WITHOUT NOTICE. C. BODY DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSION, NOT TO EXCEED 0.25MM (0.010IN). ...

Page 22

... WM8726 IMPORTANT NOTICE Wolfson Microelectronics plc (“Wolfson”) products and services are sold subject to Wolfson’s terms and conditions of sale, delivery and payment supplied at the time of order acknowledgement. Wolfson warrants performance of its products to the specifications in effect at the date of shipment. Wolfson reserves the right to make changes to its products and specifications or to discontinue any product or service without notice ...