SLES211C February   2008  – July 2015 PCM1681 , PCM1681-Q1

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Description (continued)
  6. Pin Configuration and Functions
  7. Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings: PCM1681
    3. 7.3 ESD Ratings: PCM1681-Q1
    4. 7.4 Recommended Operating Conditions
    5. 7.5 Thermal Information
    6. 7.6 Electrical Characteristics
    7. 7.7 Interface Timing Requirements
    8. 7.8 Typical Characteristics
      1. 7.8.1 Digital Filter (De-Emphasis Off)
      2. 7.8.2 De-Emphasis Filter
      3. 7.8.3 Analog Filter
      4. 7.8.4 Analog Dynamic Performance
        1. 7.8.4.1 Supply Voltage Characteristics
        2. 7.8.4.2 Temperature Characteristics
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 System Clock Input
      2. 8.3.2 Power-on-Reset Function
      3. 8.3.3 Audio Serial Interface
      4. 8.3.4 Audio Data Formats and Timing
      5. 8.3.5 De-Emphasis Filter
      6. 8.3.6 Oversampling Rate Control
      7. 8.3.7 Zero Flag
      8. 8.3.8 Mode Control
        1. 8.3.8.1 Parallel Hardware Control
        2. 8.3.8.2 SPI Control Interface
        3. 8.3.8.3 Analog Outputs
          1. 8.3.8.3.1 VCOM Output
        4. 8.3.8.4 Register Write Operation
        5. 8.3.8.5 Interface Timing Requirements
    4. 8.4 Device Functional Modes
      1. 8.4.1 Control Modes
      2. 8.4.2 Audio Modes
    5. 8.5 Programming
      1. 8.5.1 I2C Interface
        1. 8.5.1.1 Slave Address
        2. 8.5.1.2 Packet Protocol
        3. 8.5.1.3 Write Operation
        4. 8.5.1.4 Read Operation
      2. 8.5.2 Mode Control Registers
        1. 8.5.2.1 User-Programmable Mode Controls
    6. 8.6 Register Maps
      1. 8.6.1 Reserved Registers
      2. 8.6.2 Register Definitions
        1. 8.6.2.1  ATx[7:0]: Digital Attenuation Level Setting
        2. 8.6.2.2  MUTx: Soft Mute Control
        3. 8.6.2.3  DACx: DAC Operation Control
        4. 8.6.2.4  FLT: Digital Filter Roll-Off Control
        5. 8.6.2.5  FMT[3:0]: Audio Interface Data Format
        6. 8.6.2.6  SRST: Reset
        7. 8.6.2.7  ZREV: Zero-Flag Polarity Select
        8. 8.6.2.8  DREV: Output Phase Select
        9. 8.6.2.9  DMF[1:0]: Sampling Frequency Selection for the De-Emphasis Function
        10. 8.6.2.10 DMC: Digital De-Emphasis All-Channel Function Control
        11. 8.6.2.11 REV[8:1]: Output Phase Select per Channel
        12. 8.6.2.12 OVER: Oversampling Rate Control
        13. 8.6.2.13 FLTx: Digital Filter Roll-Off Control per DATA Group
        14. 8.6.2.14 DAMS: Digital Attenuation Mode Select
        15. 8.6.2.15 AZRO[1:0]: Zero-Flag Channel-Combination Select
        16. 8.6.2.16 ZERO[8:1]: Zero-Detect Status (Read-Only, I2C Interface Only)
  9. Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 D/A Output Filter Circuits
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Hardware Control Method
        2. 9.2.2.2 Audio Input
        3. 9.2.2.3 Audio Output
        4. 9.2.2.4 Master Clock
      3. 9.2.3 Application Curve
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Related Links
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8 Detailed Description

8.1 Overview

The PCM1681 and PCM1681-Q1 are CMOS monolithic integrated circuits which feature an eight-channel 24-bit audio digital-to-analog converter (DAC) and support circuitry in small 28-lead TSSOP PowerPAD packages. The DACs utilize a Burr-Brown enhanced multilevel delta-sigma (ΔΣ) architecture to achieve excellent signal-to-noise performance and a high tolerance to clock jitter. The system clock can operate anywhere from 128 fs to 1152 fs and with respect to the system clock rate the DAC can oversample anywhere from ×16 to ×128. The PCM1681 and PCM1681-Q1 accept TDM (time-division multiplexed) format in addition to industry-standard audio data formats with 16- to 24-bit audio data width. This includes right justified, I2S, left justified, and DSP formats along with sampling rates up to 200 kHz. The PCM1681 and PCM1681-Q1 provide a sub-set of user-programmable functions through a parallel control port, in addition to a full set of user-programmable functions through a serial control port, SPI, or I2C. This is controlled through the MSEL pin as explained in Table 7. A 5-V analog supply and a 3.3-V digital supply are required. The PCM1681 supports –40°C to 85°C for consumer grade applications and the PCM1681-Q1 supports –40°C to 105°C for automotive audio grade systems.

8.2 Functional Block Diagram

PCM1681 PCM1681-Q1 fbd2_sles211.gif

8.3 Feature Description

8.3.1 System Clock Input

The PCM1681 and PCM1681-Q1 require a system clock for operating the digital interpolation filters and multilevel ΔΣ modulators. The system clock is applied at the SCK input (pin 5). Table 1 shows examples of system clock frequencies for common audio sampling rates.

Figure 21 shows the timing requirements for the system clock input. For optimal performance, it is important to use a clock source with low phase jitter and noise. A Texas Instruments PLL170x multi-clock generator is an excellent choice for providing the PCM1681 and PCM1681-Q1 system clock source.

Table 1. System Clock Frequencies for Common Audio Sampling Frequencies

SAMPLING FREQUENCY SYSTEM CLOCK FREQUENCY (fSCK), MHz
128 fS 192 fS 256 fS 384 fS 512 fS 768 fS 1152 fS
8 kHz 1.024 1.536 2.048 3.072 4.096 6.144 9.216
16 kHz 2.048 3.072 4.096 6.144 8.192 12.288 18.432
32 kHz 4.096 6.144 8.192 12.288 16.384 24.576 36.864
44.1 kHz 5.6448 8.4672 11.2896 16.9344 22.5792 33.8688 (1)
48 kHz 6.144 9.216 12.288 18.432 24.576 36.864 (1)
88.2 kHz 11.2896 16.9344 22.5792 33.8688 (1) (1) (1)
96 kHz 12.288 18.432 24.576 36.864 (1) (1) (1)
192 kHz 24.576 36.864 (1) (1) (1) (1) (1)
(1) This system clock frequency is not supported for the given sampling frequency.
PCM1681 PCM1681-Q1 les211_5a08_2.gif
1. System clock pulse cycle time; 1/128 fS, 1/192 fS, 1/256 fS, 1/384 fS, 1/512 fS, 1/768 fS, or 1/1152 fS
Figure 21. System Clock Timing Diagram

Table 2. System Clock Timing

PARAMETER MIN MAX UNIT
tc(SCK) System clock cycle time 25 ns
tw(SCKH) System clock pulse duration, HIGH 10 ns
tw(SCKL) System clock pulse duration, LOW 10 ns
System clock duty cycle 40% 60%

8.3.2 Power-on-Reset Function

The PCM1681 and PCM1681-Q1 include a power-on-reset function. Figure 22 shows the operation of this function. With the system clock active and VDD > 2.2 V (typical, 1.4 V to 2.9 V), the power-on-reset function is enabled. The initialization sequence requires 65,536 system clocks from the time VDD > 2.2 V. VDD must rise up with a ramp-up rate greater than 1V/ms to ensure reliable initialization. After the initialization period, the PCM1681 and PCM1681-Q1 are set to the respective reset default state, as described in the Mode Control Registers section of this data sheet.

During the reset period (65,536 system clocks), the analog output is forced to the common voltage (VCOM), or VCC/2. After the reset period, the internal register is initialized in the next 1/fS period and if SCK, BCK, and LRCK are provided continuously, the PCM1681 and PCM1681-Q1 provide the proper analog output with group delay corresponding to the input data.

PCM1681 PCM1681-Q1 pwro_tim_2_les211.gifFigure 22. Power-On-Reset Timing

8.3.3 Audio Serial Interface

The audio serial interface for the PCM1681 and PCM1681-Q1 is comprised of a 6-wire synchronous serial port. It includes LRCK (pin 8), BCK (pin 7), and DATA1 (pin 6), DATA2 (pin 11), DATA3 (pin 12), and DATA4 (pin 13). BCK is the serial audio bit clock, and it is used to clock the serial data present on DATA1, DATA2, DATA3, and DATA4 into the audio interface serial shift register. Serial data are clocked into the PCM1681 and PCM1681-Q1 on the rising edge of BCK. LRCK is the serial audio left/right word clock. It is used to latch serial data into the serial audio interface internal registers.

Both LRCK and BCK must be synchronous with the system clock, SCK. Ideally, it is recommended that LRCK and BCK are derived from SCK. LRCK is operated at the sampling frequency, fS. BCK can be operated at 32, 48, or 64 times the sampling frequency for the PCM formats and times at 128 and 256 the sampling frequency for the TDM formats.

Internal operation of the PCM1681 and PCM1681-Q1 is synchronized with LRCK. Accordingly, internal operation is suspended when LRCK is changed or when SCK and/or BCK is interrupted for at least 3-bit clock cycles. If SCK, BCK, and LRCK are provided continuously after this held condition, the internal operation is resynchronized automatically within the following 3/fS period. External resetting is not required.

8.3.4 Audio Data Formats and Timing

The PCM1681 and PCM1681-Q1 support industry-standard audio data formats, including right-justified, I2S, left-justified, and DSP. The PCM1681 and PCM1681-Q1 also support a time-division-multiplexed (TDM) format. The TDM format is supported only at system clocks of 128 fS, 256 fS, and 512 fS. The data formats are shown in Figure 23 and Figure 24. Data formats are selected using the format bits, FMT[3:0], located in control register 9 of the PCM1681 and PCM1681-Q1. The default data format is 16- to 24-bit left-justified. All formats require binary 2s complement, MSB-first audio data. Figure 25 shows a detailed timing diagram for the serial audio interface.

DATA1, DATA2, DATA3, and DATA4 each carry two audio channels, designated as the left and right channels in the right-justified, I2S, left-justified, and DSP formats. The left-channel data always precedes the right-channel data in the serial data stream for all data formats. Table 3 shows the mapping of the digital input data to the analog output pins. DATA1 carries eight audio channels in 256 fS mode TDM fornat, and DATA1 and DATA2 each carry four audio channels in 128 fS mode TDM format.

Table 3. Audio Input Data to Analog Output Mapping

DATA INPUT CHANNEL ANALOG OUTPUT
DATA1 Left VOUT1
Right VOUT2
DATA2 Left VOUT3
Right VOUT4
DATA3 Left VOUT5
Right VOUT6
DATA4 Left VOUT7
Right VOUT8
PCM1681 PCM1681-Q1 dta_fmts_2_les211.gifFigure 23. Audio Data Input Formats
PCM1681 PCM1681-Q1 dsp_fmt_les211.gifFigure 24. Audio Data Input Formats
PCM1681 PCM1681-Q1 aud_tim_2_les211.gifFigure 25. Audio Interface Timing Diagram

Table 4. Audio Interface Timing

PARAMETER MIN MAX UNIT
t(BCY) BCK cycle time 75(1) ns
t(BCH) BCK pulse duration HIGH 35 ns
t(BCL) BCK pulse duration LOW 35 ns
t(LRW) LRCK pulse duration HIGH, right-justified, I2S, left-justified 1/2 fS 1/2 fS
LRCK pulse duration HIGH, DSP format t(BCY) t(BCY)
LRCK pulse duration HIGH, TDM format t(BCY) 1/fS – t(BCY)
t(LS) LRCK setup time to BCK rising edge 10 ns
t(LH) LRCK hold time to BCK rising edge 10 ns
t(DS) DATA1, DATA2, DATA3, DATA4 setup time to BCK rising edge 10 ns
t(DH) DATA1, DATA2, DATA3, DATA4 hold time to BCK rising edge 10 ns
(1) For right-justified, I2S, left-justified, and DSP formats, there is no fS (sampling frequency) limitation for all of 1/32 fS, 1/48 fS, or 1/64 fS. However, for TDM format, allowable fS is limited to fS ≤ 50 kHz for BCK = 256 fS mode and fS ≤ 100 kHz for BCK = 128 fS mode.

8.3.5 De-Emphasis Filter

The PCM1681 and PCM1681-Q1 include a digital de-emphasis filter for 32 kHz, 44.1 kHz, and 48 kHz sampling frequencies.

8.3.6 Oversampling Rate Control

The PCM1681 and PCM1681-Q1 automatically control the oversampling rate of the ΔΣ DACs according to system clock frequency and oversampling mode. Oversampling mode, narrow or wide, can be selected by the MSEL pin in H/W control mode and the OVER bit of control register 12 in S/W control mode. The oversampling rate is set to 64× oversampling with a 1152 fS, 768 fS, 512 fS system clock, 32× oversampling with a 384 fS, 256 fS system clock, and 16× oversampling with a 192 fS, 128 fS system clock in default, narrow mode, and 128× oversampling with a 1152 fS, 768 fS, 512 fS system clock, 64× oversampling with a 384 fS, 256 fS system clock, and 32× oversampling with a 192 fS, 128 fS system clock in wide mode. Wide mode is recommended for fS ≤ 96 kHz at SCK = 128 fS or 192 fS, fS ≤ 48 kHz at SCK = 256 fS or 384 fS, and fS ≤ 24 kHz at SCK = 512 fS, 768 fS, or 1152 fS.

Table 5. Oversampling Rate Control

OVERSAMPLING MODE OVERSAMPLING RATE
SCK = 128 fS or 192 fS SCK = 256 fS or 384 fS SCK = 512 fS, 768 fS, or 1152 fS
Narrow mode 16× 32× 64×
Wide mode 32× 64× 128×

8.3.7 Zero Flag

The PCM1681 and PCM1681-Q1 have two zero-flag pins, ZR1 (pin 1) and ZR2 (pin 28), which are assigned to the combinations A through D as shown in Table 6. Zero-flag combinations are selected using the zero-flag combination bits, AZRO[1:0], located in control register 13 of the PCM1681 and PCM1681-Q1. If the input data of the L-channel and/or R-channel of all assigned channels remains at a logic-0 level for 1024 sampling periods (LRCK clock periods), ZR1 and ZR2 are set to logic-1 states, or high level. If the input data of any of the assigned channels contains a logic-1 level, ZR1 and ZR2 are set to logic-0 states or low level immediately.

The active polarity of a zero-flag output can be inverted by setting the ZREV bit of control register 10 to 1. The reset default is ZREV = 0, active-high for zero detection.

In parallel hardware control mode, ZR1 is not applicable due to the reassignment of ZR1 as the FMT0 control pin, and the zero-flag output combination is fixed as all 8 channel (DATA1-DATA4) data zero on the ZR2 pin.

Table 6. Zero-Flag Output Combinations

ZERO-FLAG COMBINATION ZR1/ZR1/FMT0 (PIN 1) ZR2 (PIN 28)
A DATA1 L-ch DATA1 R-ch
B DATA1-4 DATA1-4
C DATA4 DATA1-3
D DATA1 DATA2-4

8.3.8 Mode Control

The PCM1681 and PCM1681-Q1 support three types of interface mode control with three types of oversampling configuration, according to the input state of MSEL (pin 14) as listed in Table 7. The required values of the pull-up and pull-down resistors are 220 kΩ ± 5%.

Table 7. Interface Mode Control

MSEL INTERFACE MODE CONTROL
Tied with DGND 2-Wire (I2C) serial control, selectable oversampling configuration
Pull-down resistor to DGND 4-Wire parallel H/W control, narrow mode oversampling configuration
Pull-up resistor to VDD 4-Wire parallel H/W control, wide mode oversampling configuration
Tied with VDD 3-Wire (SPI) serial control, selectable oversampling configuration

The input state of the MSEL pin is sampled at power-on with the system clock input; therefore, an input change after a reset is ignored until the next power-on. The assignments of the four pins are controlled by the interface mode control setting as listed in Table 8.

Table 8. Interface Mode Control Pin Assignments

PIN DEFINITION (Assignment)
I2C SPI PARALLEL H/W
4 SDA (input/output) MD (input) MUTE (input)
3 SCL (input) MC (input) DEMP (input)
2 ADR (input) MS (input) FMT1 (input)
1 ZR1 (output) ZR1 (output) FMT0 (input)

In serial control mode, actual mode control is performed by a register write (and read) through the I2C or SPI compatible serial control port. In parallel H/W control mode, the specific four functions are controlled directly through high-level/low-level control of five specific pins (see Parallel Hardware Control section), and the zero-flag function of ZR1 is not applicable.

8.3.8.1 Parallel Hardware Control

Four functions are controlled by five pins, MSEL, FMT0, FMT1, DEMP, and MUTE in parallel hardware control mode.

MSEL TERMINATION(1) DESCRIPTION
Pull-down resistor to DGND Narrow oversampling mode
Pull-up resistor to VDD Wide oversampling mode
(1) The MSEL termination controls the oversampling mode for all eight channels.
FMT1(1) FMT0(1) DESCRIPTION
LOW LOW 24-bits right-justified format
LOW HIGH 16 to 24-bits I2S format
HIGH LOW 16 to 24-bits left-justified format
HIGH HIGH 24-bits I2S mode TDM format
(1) The FMT0 and FMT1 pins control the audio interface format for all eight channels.
DEMP(1) DESCRIPTION
LOW De-emphasis off
HIGH 44.1-kHz De-emphasis on
(1) The DEMP pin controls the 44.1-kHz digital de-emphasis function of all eight channels.
MUTE(1) DESCRIPTION
LOW Mute off (mute disable)
HIGH Mute on (mute enable)
(1) The MUTE pin controls all 8 channel outputs at the same time.

8.3.8.2 SPI Control Interface

The SPI control interface of the PCM1681 and PCM1681-Q1 is a 3-wire synchronous serial port that operates asynchronously to the serial audio interface. The SPI control interface is used to program the on-chip mode registers. The control interface includes MD (pin 4), MC (pin 3), and MS (pin 2). MD is the serial data input, used to program the mode registers. MC is the control port for the serial bit clock, used to shift in the serial data, and MS is the control port for mode control select, which is used to enable the mode control. The SPI control interface is available when MSEL (pin 14) is tied with VDD and after power-on reset completion.

8.3.8.3 Analog Outputs

The PCM1681 and PCM1681-Q1 include eight independent output channels, VOUT1 through VOUT8. These are unbalanced outputs, each capable of driving 3.75 VPP typical into a 5-kΩ ac load with VCC = 5 V. The internal output amplifiers for VOUT1 through VOUT8 are biased to the dc common voltage, equal to 0.486 VCC.

The output amplifiers include an RC continuous-time filter, which helps to reduce the out-of-band noise energy present at the DAC outputs due to the noise-shaping characteristics of the PCM1681 and PCM1681-Q1 ΔΣ DACs. The frequency response of this filter is shown in Figure 12. By itself, this filter is not enough to attenuate the out-of-band noise to an acceptable level for most applications. An external low-pass filter is required to provide sufficient out-of-band noise rejection. Further discussion of DAC post-filter circuits is provided in the Application and Implementation section of this data sheet.

8.3.8.3.1 VCOM Output

One unbuffered common voltage output pin, VCOM (pin 25), is brought out for decoupling purposes. This pin is nominally biased to the dc common voltage, equal to VCC/2. If this pin is to be used to bias external circuitry, a voltage follower is required for buffering purposes. Figure 26 shows an example of a 5-V single-supply filter circuit using the VCOM pin for external biasing applications.

PCM1681 PCM1681-Q1 ai_1sup_filt_vcom_les211.gif

NOINDENT:

Example:
R1: 6.2 kΩ
R2: 6.8 kΩ
R3: 430 Ω
C1: 470 pF
C2: 4700 pF
AV: –1.10 (1.45 Vrms Output)
fC: 70 kHz
Figure 26. Single-Supply Filter Circuit Using VCOM for External Biasing Applications

8.3.8.4 Register Write Operation

All write operations for the serial control port use 16-bit data words. Figure 27 shows the control data word format. The most significant bit is a fixed 0 for the write operation. Seven bits, labeled IDX[6:0], set the register index (or address) for the write operation. The least significant eight bits, D[7:0], contain the data to be written to the register specified by IDX[6:0].

Figure 28 shows the functional timing diagram for writing to the serial control port. MS is held at a logic-1 state until a register needs to be written. To start the register write cycle, MS is set to logic-0. 16 clock cycles are then provided on MC, corresponding to the 16 bits of the control data word on MD. After completion of the 16th clock cycle, MS is set to logic-1 to latch the data into the indexed mode control register.

PCM1681 PCM1681-Q1 r0001-01_2.gifFigure 27. Control Data Word Format for MD
PCM1681 PCM1681-Q1 t0048-01_2.gifFigure 28. Write Operation Timing

8.3.8.5 Interface Timing Requirements

Figure 29 shows a detailed timing diagram for the serial control interface. Special attention to the setup and hold times is required. Also, t(MSS) and t(MSH), which define the minimum delays between the edges of the MS and MC clocks, require special attention. These timing parameters are critical for proper control port operation.

PCM1681 PCM1681-Q1 t0013-03_2.gifFigure 29. Interface Timing Diagram

Table 9. Interface Timing

PARAMETER MIN UNIT
t(MCY) MC cycle time 100 ns
t(MCL) MC pulse duration, LOW 50 ns
t(MCH) MC pulse duration, HIGH 50 ns
t(MHH) MS pulse duration, HIGH ns(1)
t(MSS) MS falling edge to MC rising edge 20 ns
t(MSH) MS hold time, MC rising edge for LSB to MS rising edge 20 ns
t(MDH) MD hold time 15 ns
t(MDS) MD setup time 20 ns
(1) 3/(256 fS) s (minimum), fS: sampling rate

8.4 Device Functional Modes

8.4.1 Control Modes

  • 3-wire SPI
  • I2C
  • Hardware Control

8.4.2 Audio Modes

  • Right or left justified
  • I2S
  • TDM
  • DSP

8.5 Programming

8.5.1 I2C Interface

The PCM1681 and PCM1681-Q1 support the I2C serial bus and the data transmission protocol for standard mode as a slave device. This protocol is explained in the I2C specification 2.0. The PCM1681 and PCM1681-Q1 do not support a board-to-board interface. The I2C control interface is available when MSEL (pin 14) is tied with DGND and after power-on reset completion.

8.5.1.1 Slave Address

MSB LSB
1 0 0 1 1 0 ADR R/W

The PCM1681 and PCM1681-Q1 have seven bits for the respective slave address. The first six bits (MSBs) of the slave address are factory preset to 1001 10. The next bit of the address byte is the device select bit, which can be user-defined using the ADR terminal. A maximum of two PCM1681s or PCM1681-Q1s can be connected on the same bus at one time. Each PCM1681 or PCM1681-Q1 responds when it receives its own slave address.

8.5.1.2 Packet Protocol

A master device must control packet protocol, which consists of a start condition, slave address, read/write bit, data if writing or acknowledge if reading, and stop condition. The PCM1681 and PCM1681-Q1 support only slave receivers and slave transmitters. The details about DATA for write and read operation are described in the following sections.

PCM1681 PCM1681-Q1 i2c_frmwrk_2_les211.gifFigure 30. Basic I2C Framework

8.5.1.3 Write Operation

A master can write to any PCM1681 and PCM1681-Q1 registers using a single access. The master sends a PCM1681 or PCM1681-Q1 slave address with a write bit, a register address, and the data. When undefined registers are accessed, the PCM1681 or PCM1681-Q1 sends an acknowledgment, but the write operation does not occur. Figure 31 is a diagram of the write operation.

PCM1681 PCM1681-Q1 r0002-01_2.gifFigure 31. Write Operation

8.5.1.4 Read Operation

A master can read any PCM1681 or PCM1681-Q1 register using a single access. The master sends a PCM1681 or PCM1681-Q1 slave address with a read bit after transferring the register address. Then the PCM1681 or PCM1681-Q1 transfers the data in the register specified. Figure 32 is a diagram of the read operation.

PCM1681 PCM1681-Q1 r0002-02_2.gif

NOTE:

The slave address after the repeated start condition must be the same as the previous slave address.
Figure 32. Read Operation

8.5.2 Mode Control Registers

8.5.2.1 User-Programmable Mode Controls

The PCM1681 and PCM1681-Q1 include a number of user-programmable functions which are accessed via control registers. The registers are programmed using the serial control interface which is discussed in the Mode Control section of this data sheet. Table 10 lists the available mode control functions, along with the respective reset default conditions and associated register index.

8.6 Register Maps

The mode control register map is shown in Table 11. The MSB of all registers is fixed to 0. Each register also includes an index (or address) indicated by the IDX[6:0] bits.

8.6.1 Reserved Registers

Registers 0 and 15 are reserved for factory use. To ensure proper operation, the user should not write to these registers.

Table 10. User-Programmable Mode Control Functions

FUNCTION RESET DEFAULT REGISTER BIT
Digital attenuation control, 0 dB to –63 dB in 0.5-dB steps 0 dB, no attenuation 1–6, 16, 17 AT1[7:0], AT2[7:0], AT3[7:0], AT4[7:0], AT5[7:0], AT6[7:0], AT7[7:0], AT8[7:0]
Soft mute control Mute disabled 7, 18 MUT[8:1], MUT[8:7]
DAC1–DAC8 operation control DAC1–DAC8 enabled 8, 19 DAC[8:1], DAC[8:7]
Audio data format control 16- to 24-bit, left-justified 9 FMT[3:0]
Digital filter roll-off control Sharp roll-off 9 FLT
De-emphasis all-channel function control De-emphasis of all channels disabled 10 DMC
De-emphasis all-channel sample rate selection 44.1 kHz 10 DMF[1:0]
Output phase select Normal phase 10 DREV
Zero-flag polarity select High 10 ZREV
Software reset control Reset disabled 10 SRST
Output phase select per channel Reverse phase 11 REV[8:1]
Oversampling rate control Narrow (×64, ×32, ×16) mode 12 OVER
Digital filter roll-off control per DATA group Slow roll-off 12 FLT[4:1]
Zero-flag combination select ZR1: DATA1 Lch
ZR2: DATA1 Rch
13 AZRO[1:0]
Digital attenuation mode select 0 to –63 dB, 0.5-dB step 13 DAMS
Zero-detect status
(read-only, I2C interface only)
N/A 14 ZERO[8:1]

Table 11. Mode Control Register Map

IDX (B8–B14) REGISTER B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
00h 0 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 N/A(1) N/A(1) N/A(1) N/A(1) N/A(1) N/A(1) N/A(1) N/A(1)
01h 1 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT17 AT16 AT15 AT14 AT13 AT12 AT11 AT10
02h 2 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT27 AT26 AT25 AT24 AT23 AT22 AT21 AT20
03h 3 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT37 AT36 AT35 AT34 AT33 AT32 AT31 AT30
04h 4 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT47 AT46 AT45 AT44 AT43 AT42 AT41 AT40
05h 5 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT57 AT56 AT55 AT54 AT53 AT52 AT51 AT50
06h 6 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT67 AT66 AT65 AT64 AT63 AT62 AT61 AT60
07h 7 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 MUT8 MUT7 MUT6 MUT5 MUT4 MUT3 MUT2 MUT1
08h 8 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 DAC8 DAC7 DAC6 DAC5 DAC4 DAC3 DAC2 DAC1
09h 9 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 RSV(2) RSV(2) FLT RSV(2) FMT3 FMT2 FMT1 FMT0
0Ah 10 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 SRST ZREV DREV DMF1 DMF0 RSV(2) RSV(2) DMC
0Bh 11 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 REV8 REV7 REV6 REV5 REV4 REV3 REV2 REV1
0Ch 12 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 OVER RSV(2) RSV(2) RSV(2) FLT4 FLT3 FLT2 FLT1
0Dh 13 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 DAMS AZRO1 AZRO0 RSV(2) RSV(2) RSV(2) RSV(2) RSV(2)
0Eh 14 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 ZERO8 ZERO7 ZERO6 ZERO5 ZERO4 ZERO3 ZERO2 ZERO1
10h 16 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT77 AT76 AT75 AT74 AT73 AT72 AT71 AT70
11h 17 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT87 AT86 AT85 AT84 AT83 AT82 AT81 AT80
12h 18 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 RSV(2) RSV(2) RSV(2) RSV(2) RSV(2) RSV(2) MUT8 MUT7
13h 19 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 RSV(2) RSV(2) RSV(2) RSV(2) RSV(2) RSV(2) DAC8 DAC7
(1) Not assigned. No operation even if setting any data
(2) Reserved for test operation. It should be set to 0 during normal operation.

8.6.2 Register Definitions

B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
REGISTER 1 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT17 AT16 AT15 AT14 AT13 AT12 AT11 AT10
REGISTER 2 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT27 AT26 AT25 AT24 AT23 AT22 AT21 AT20
REGISTER 3 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT37 AT36 AT35 AT34 AT33 AT32 AT31 AT30
REGISTER 4 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT47 AT46 AT45 AT44 AT43 AT42 AT41 AT40
REGISTER 5 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT57 AT56 AT55 AT54 AT53 AT52 AT51 AT50
REGISTER 6 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT67 AT66 AT65 AT64 AT63 AT62 AT61 AT60
REGISTER 16 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT77 AT76 AT75 AT74 AT73 AT72 AT71 AT70
REGISTER 17 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 AT87 AT86 AT85 AT84 AT83 AT82 AT81 AT80

8.6.2.1 ATx[7:0]: Digital Attenuation Level Setting

where x = 1–8, corresponding to the DAC output VOUTx. Default value: 1111 1111b

ATx[7:0] DECIMAL VALUE ATTENUATION LEVEL SETTING
DAMS = 0 DAMS = 1
1111 1111b 255 0 dB, no attenuation (default) 0 dB, no attenuation (default)
1111 1110b 254 –0.5 dB –1 dB
1111 1101b 253 –1 dB –2 dB
: : : :
1001 1100b 156 –49.5 dB –99 dB
1001 1011b 155 –50 dB –100 dB
1001 1010b 154 –50.5 dB Mute
: : : :
1000 0010b 130 –62.5 dB Mute
1000 0001b 129 –63 dB Mute
1000 0000b 128 Mute Mute
: : : :
0000 0000b 0 Mute Mute

Each DAC output, VOUT1 through VOUT8, has a digital attenuation function. The attenuation level can be set from 0 dB to R dB, in S-dB steps. Changes in attenuation levels are made by incrementing or decrementing by one step (S-dB) for every 8/fS time interval until the programmed attenuation setting is reached. Alternatively, the attenuation level can be set to infinite attenuation (or mute). Range (R) and step (S) are –63 and 0.5, respectively, for DAMS = 0 and –100 and 1, respectively, for DAMS = 1. The DAMS bit is defined in register 13. The attenuation data for each channel can be set individually. The attenuation level can be calculated using the following formula:

where

    where ATx[7:0]DEC = 0 through 255. For ATx[7:0]DEC = 0 through 128 with DAMS = 0 or for ATx[7:0]DEC = 0 through 154 with DAMS = 1, the attenuation is set to infinite attenuation (mute).

    B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
    REGISTER 7 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 MUT8 MUT7 MUT6 MUT5 MUT4 MUT3 MUT2 MUT1
    REGISTER 18 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 RSV RSV RSV RSV RSV RSV MUT8 MUT7

    8.6.2.2 MUTx: Soft Mute Control

    where x = 1–8, corresponding to the DAC output VOUTx. Default value: 0

    MUTx SOFT MUTE CONTROL
    0 Mute disabled (default)
    1 Mute enabled

    The mute bits, MUT1 through MUT8, are used to enable or disable the soft mute function for the corresponding DAC outputs, VOUT1 through VOUT8. MUT7 and MUT8 of register 7 and register 18 work as an OR function, either one or both can be used according to the requirements of the application. The soft mute function is incorporated into the digital attenuators. When mute is disabled (MUTx = 0), the attenuator and DAC operate normally. When mute is enabled by setting MUTx = 1, the digital attenuator for the corresponding output is decreased from the current setting to the infinite-attenuation setting one attenuator step (S-dB) at a time. This provides a quiet, pop-free muting of the DAC output. On returning from soft mute, by setting MUTx = 0, the attenuator is increased one step at a time to the previously programmed attenuator level. The step size, S, is 0.5 dB for DAMS = 0 and 1 dB for DAMS = 1.

    B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
    REGISTER 8 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 DAC8 DAC7 DAC6 DAC5 DAC4 DAC3 DAC2 DAC1
    REGISTER 19 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 RSV RSV RSV RSV RSV RSV DAC8 DAC7

    8.6.2.3 DACx: DAC Operation Control

    where x = 1–8, corresponding to the DAC output VOUTx. Default value: 0

    DACx DAC OPERATION CONTROL
    0 DAC operation enabled (default)
    1 DAC operation disabled

    The DAC operation controls are used to enable and disable the DAC outputs, VOUT1 through VOUT8. When DACx = 0, the output amplifier input is connected to the DAC output. When DACx = 1, the output amplifier input is switched to the dc common voltage (VCOM), equal to VCC/2. DAC7 and DAC8 of register 8 and register 19 work as an OR function, either one or both can be used according to the requirements of the application.

    B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
    REGISTER 9 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 RSV RSV FLT RSV FMT3 FMT2 FMT1 FMT0

    8.6.2.4 FLT: Digital Filter Roll-Off Control

    Default value: 0

    FLT DIGITAL FILTER ROLL-OFF CONTROL
    0 Sharp roll-off (default)
    1 Slow roll-off

    The FLT bit allows users to select the digital filter roll-off that is best suited to their application. Two filter roll-off selections are available: sharp or slow. The filter responses for these selections are shown in the Typical Characteristics section of this data sheet.

    8.6.2.5 FMT[3:0]: Audio Interface Data Format

    Default value: 0101b

    FMT[3:0] AUDIO DATA FORMAT SELECTION
    0000 Right-justified format, 24-bit
    0001 Reserved
    0010 Reserved
    0011 Right-justified format, 16-bit
    0100 I2S format, 16- to 24-bit
    0101 Left-justified format, 16- to 24-bit (default)
    0110 I2S format, TDM format, 24-bit
    0111 Left-justified format, TDM format, 24-bit
    1000 I2S format, DSP format, 24-bit
    1001 Left-justified format, DSP format, 24-bit

    The FMT[3:0] bits are used to select the data format for the serial audio interface.

    The format details and restrictions related with the system clock are described in the section Audio Data Formats and Timing.

    B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
    REGISTER 10 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 SRST ZREV DREV DMF1 DMF0 RSV RSV DMC

    8.6.2.6 SRST: Reset

    Default value: 0

    SRST RESET
    0 Reset disabled (default)
    1 Reset enabled

    The SRST bit is used to enable or disable the soft reset function. The operation is the same as the power-on-reset function with the exception of the reset period, which is 1024 system clocks for the SRST function. All registers are initialized.

    8.6.2.7 ZREV: Zero-Flag Polarity Select

    Default value: 0

    ZREV ZERO-FLAG POLARITY SELECT
    0 Zero-flag pins high at a zero detect (default)
    1 Zero-flag pins low at a zero detect

    The ZREV bit allows the user to select the polarity of the zero-flag pins.

    8.6.2.8 DREV: Output Phase Select

    Default value: 0

    DREV OUTPUT PHASE SELECT
    0 Normal output (default)
    1 Inverted output

    The DREV bit allows the user to select the phase of the analog output signal.

    8.6.2.9 DMF[1:0]: Sampling Frequency Selection for the De-Emphasis Function

    Default value: 00b

    DMF[1:0] DE-EMPHASIS SAMPLING RATE SELECTION
    00 44.1 kHz (default)
    01 48 kHz
    10 32 kHz
    11 Reserved

    The DMF[1:0] bits select the sampling frequency used for the digital de-emphasis function when it is enabled. The de-emphasis curves are shown in the Typical Characteristics section of this data sheet. The preceding table shows the available sampling frequencies.

    8.6.2.10 DMC: Digital De-Emphasis All-Channel Function Control

    Default value: 0

    DMC DIGITAL DE-EMPHASIS ALL-CHANNEL FUNCTION CONTROL
    0 De-emphasis disabled for all channels (default)
    1 De-emphasis enabled for all channels

    The DMC bit is used to enable or disable the de-emphasis function for all channels.

    B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
    REGISTER 11 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 REV8 REV7 REV6 REV5 REV4 REV3 REV2 REV1

    8.6.2.11 REV[8:1]: Output Phase Select per Channel

    Where x = 1 – 8, corresponding to the DAC output VOUTx. Default value: 1

    REVx OUTPUT PHASE SELECT PER CHANNEL
    0 Normal output
    1 Inverted output (default)

    The REVx bit allows the user to select the phase of the analog output signal per channel when DREV = 1 is set on Register 10.

    B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
    REGISTER 12 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 OVER RSV RSV RSV FLT4 FLT3 FLT2 FLT1

    8.6.2.12 OVER: Oversampling Rate Control

    Default value: 0

    OVER 512 fS, 768 fS, 1152 fS 256 fS, 384 fS 128 fS, 192 fS
    0 ×64 oversampling, narrow mode (default) ×32 oversampling, narrow mode (default) ×16 oversampling, narrow mode (default)
    1 ×128 oversampling, wide mode ×64 oversampling, wide mode ×32 oversampling, wide mode

    8.6.2.13 FLTx: Digital Filter Roll-Off Control per DATA Group

    Where x = 1 – 4, corresponding to the DATAx. Default value: 1

    FLTx DIGITAL FILTER ROLL-OFF CONTROL PER DATA GROUP
    0 Sharp roll-off
    1 Slow roll-off (default)

    The FLTx bit allows the user to select the digital filter roll-off characteristic per 2 channels when FLT = 1 is set, so that it is best suited to the application. Two filter roll-off sections are available: sharp or slow. The filter responses for these selections are shown in the Typical Characteristics section.

    B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
    REGISTER 13 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 DAMS AZRO1 AZRO0 RSV RSV RSV RSV RSV

    8.6.2.14 DAMS: Digital Attenuation Mode Select

    Default value: 0

    DAMS DIGITAL ATTENUATION MODE SELECT
    0 Fine step, 0.5 dB/step for 0 to –63 dB range (default)
    1 Wide range, 1 dB/step for 0 to –100 dB range

    The DAMS bit is used to select the digital attenuation mode.

    8.6.2.15 AZRO[1:0]: Zero-Flag Channel-Combination Select

    Default value: 00b

    AZRO[1:0] ZERO-FLAG CHANNEL-COMBINATION SELECT
    00 Combination A (ZR1: DATA1 L-ch, ZR2: DATA1 R-ch) (default)
    01 Combination B (ZR1: DATA1–DATA4, ZR2: DATA1–DATA4)
    10 Combination C (ZR1: DATA4, ZR2: DATA1–DATA3)
    11 Combination D (ZR1: DATA1, ZR2: DATA2–DATA4)

    The AZRO[1:0] bits are used to select the zero-flag channel combinations for ZR1 and ZR2.

    B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
    REGISTER 14 0 IDX6 IDX5 IDX4 IDX3 IDX2 IDX1 IDX0 ZERO8 ZERO7 ZERO6 ZERO5 ZERO4 ZERO3 ZERO2 ZERO1

    8.6.2.16 ZERO[8:1]: Zero-Detect Status (Read-Only, I2C Interface Only)

    Default value: N/A

    The ZERO[8:1] bits show the status of zero detect for each channel. The status is set to 1 by detecting a zero state without regard to the ZREV bit setting.