background image

IMPORTANT NOTICE

Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other
changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest
issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and
complete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale
supplied at the time of order acknowledgment.

TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s terms
and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessary
to support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarily
performed.

TI assumes no liability for applications assistance or the design of Buyers’ products. Buyers are responsible for their products and
applications using TI components. To minimize the risks associated with Buyers’ products and applications, Buyers should provide
adequate design and operating safeguards.

TI 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 relating to any combination, machine, or process in which TI components or services are used. Information
published by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty or
endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the
third party, or a license from TI under the patents or other intellectual property of TI.

Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration
and is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altered
documentation. Information of third parties may be subject to additional restrictions.

Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service
voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice.
TI is not responsible or liable for any such statements.

Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements
concerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or support
that may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which
anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause
harm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the use
of any TI components in safety-critical applications.

In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI’s goal is to
help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and
requirements. Nonetheless, such components are subject to these terms.

No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties
have executed a special agreement specifically governing such use.

Only those TI components which TI has specifically designated as military grade or “enhanced plastic” are designed and intended for use in
military/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI components
which have

not

been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal and

regulatory requirements in connection with such use.

TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use of
non-designated products, TI will not be responsible for any failure to meet ISO/TS16949.

Products

Applications

Audio

www.ti.com/audio

Automotive and Transportation

www.ti.com/automotive

Amplifiers

amplifier.ti.com

Communications and Telecom

www.ti.com/communications

Data Converters

dataconverter.ti.com

Computers and Peripherals

www.ti.com/computers

DLP® Products

www.dlp.com

Consumer Electronics

www.ti.com/consumer-apps

DSP

dsp.ti.com

Energy and Lighting

www.ti.com/energy

Clocks and Timers

www.ti.com/clocks

Industrial

www.ti.com/industrial

Interface

interface.ti.com

Medical

www.ti.com/medical

Logic

logic.ti.com

Security

www.ti.com/security

Power Mgmt

power.ti.com

Space, Avionics and Defense

www.ti.com/space-avionics-defense

Microcontrollers

microcontroller.ti.com

Video and Imaging

www.ti.com/video

RFID

www.ti-rfid.com

OMAP Applications Processors

www.ti.com/omap

TI E2E Community

e2e.ti.com

Wireless Connectivity

www.ti.com/wirelessconnectivity

Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265

Copyright © 2014, Texas Instruments Incorporated

Summary of Contents for TAS54 4C Series

Page 1: ...on 12 1 7 Load Diagnostics 13 1 8 Power Supply 15 1 9 Charge Pump 15 1 10 EMI and PCB Layout Considerations 16 1 11 Filtering 16 1 12 Paralleling Outputs 17 1 13 Mute 17 1 14 Standby 17 1 15 Line Output 18 1 16 Harmonic Crosstalk 18 1 17 THD N Versus Frequency 19 2 TAS54x4C Software Design Guidelines 20 2 1 Definitions 20 2 2 Power Up and Initialization 21 2 3 Using the Device to Play Music 22 2 4...

Page 2: ... Handling 25 15 Channel Fault Handling 26 16 Mode Summary Excluding Faults 26 List of Tables 1 Oscillator Configuration and I2 C Addresses 4 2 Recommended Switching Frequencies for AM Mode Operation 7 3 Load Diagnostic Timing 14 2 TAS54x4C Design Guide SLOA196 June 2014 Submit Documentation Feedback Copyright 2014 Texas Instruments Incorporated ...

Page 3: ...apacitor values for the TAS54x4C devices are 0 47 µF or 1 µF For a 0 47 µF capacitor with 20 tolerance the highest cutoff frequency can be calculated using 60 kΩ and 0 38 µF The worst case cutoff frequency for this example is 7 1 Hz which allows for flat gain in the audio band The common mode rejection ratio CMRR is also affected by the input circuit The balanced inputs of the TAS5424C must have e...

Page 4: ...dress is determined by the DC voltage present on the address selection pin The I2 C address pin voltage is sensed when the device is released from standby mode This voltage is then latched at 300 µs Therefore any noise or voltage glitch cannot change the I2 C address during operation Because this pin latches when released from standby a capacitor is not necessary on this pin The charge time on the...

Page 5: ...z These three frequencies synchronize the ICs and are present on the OSC_SYNC pin This oscillator is then divided again by 8 to provide 500 kHz 417 kHz and 357 kHz switching frequency options The divide ratio is set through the I2 C 1 3 1 Oscillator Synchronization Some designs require more than one TAS54xx device As previously mentioned in Section 1 2 one I2 C bus can have up to four separate dev...

Page 6: ...0 offset by 90 which is half of the switching phase 45 Phase 180 Phase Figure 2 Clock Synchronization Options NOTE The PCB layout for the OSC_SYNC should be a direct route or the shortest route from the master to slave devices for best operation A star connection is preferred instead of a daisy chain The REXT resistor that sets the 20 MHz oscillator must still be used in the slave devices The 20 M...

Page 7: ...ality This variation moves the oscillator frequency enough to avoid the AM receiver from locking on the frequency and producing a tone The next design characteristic for dither is to determine the dither frequency or how fast the REXT pin current changes Any change in the PWM frequency is demodulated as an output signal Because the TAS54x4C devices have feedback this change is reduced by the amoun...

Page 8: ... A bypass capacitor C BYPASS must be included in the design because it is part of the current path for snubbing the inductance of the high side FET The terminals of C BYPASS must be close to the PVDD pins and the PGND pins of the IC Rx and Cx should be close to the output pin and the PGND pins of the IC This necessary to reduce the series inductance of the PCB traces The current loops that are for...

Page 9: ... of the calculated Rx Too high a value for the Rx could allow for a spike but too low of a value for Rx could cause the snubber to draw excessive current and overheat Use Equation 5 to calculate the power loss in the resistor P Cx V2 ƒS where V is the voltage at PVDD ƒS is the switching frequency 5 1 4 2 Demodulation Filter Design An output LC demodulation filter is required to reconstruct the aud...

Page 10: ...ance is infinity and therefore the value of Q would be infinity also See Equation 7 7 The peak of the Q value is located at ƒCO The signal at this frequency is greatly amplified and can be measured on an oscilloscope This signal is seen as a sine wave and can be mistaken as an oscillating amplifier 1 5 Component Selection 1 5 1 Inductors When the inductance value has been determined three addition...

Page 11: ... resistance increases less power is delivered to the loudspeakers and more power is dissipated in the voice coil creating more heat in the voice coil increasing RDC further The RDC is determined by the amplifier power and nominal speaker impedance A 25 W rated amplifier into a 4 Ω speaker should use an inductor with a maximum RDC of 25 mΩ When either amplifier power increases or speaker impedance ...

Page 12: ...just the volume level or reduce bass in the system so that the amplifier will not produce more heat This warning can also be used to turn on a system fan 1 6 3 DC Offset In a car environment with extreme temperature and humidity changes electronic components such as electrolytic capacitors can become leaky over time If this capacitor is used in series with the input signal and it becomes leaky and...

Page 13: ...r or speaker wires could be shorted shorted load the speaker wires could be shorted to ground and the speaker wires could be shorted to power or battery The TAS54x4C devices have the ability to test all of the channels at the same time or each channel individually for a proper load The load diagnostics are instigated through an I2 C command See Figure 13 for a flowchart of the load diagnostics In ...

Page 14: ...short to ground failure occurs if any output does not reach either PVDD pin Likewise if any output does not reach the ground a short to power failure occurs If a boosted PVDD is used the S2P test can still detect a short to battery The OL and SL tests derive the signal by charging and discharging the MUTE capacitor This signal is directed to the output pins The signal is measured differentially ac...

Page 15: ... the power supply can be the battery of the vehicle These devices have feedback around the class D amplifier to provide a fixed gain As in many class D amplifiers the gain is dependent on the power supply voltage but with feedback this is not the case Additional circuits have been added to improve the power supply rejection ratio PSRR further The need for wideband PSRR is to remove high frequency ...

Page 16: ...s to use a four layer PCB with all the traces with high current or clocks on the inner layers with vias to connect them to the parts The outer layers are reserved for ground planes which creates a Faraday cage around the whole PCB reducing the EMI emanated from the PCB 1 11 Filtering 1 11 1 Power Supply Filtering The power supply is tested for both conducted and radiated emissions The first test i...

Page 17: ...el 2 The channel 1 input can be left disconnected When channels 3 and 4 are paralleled the input signal is placed on channel 3 and the input on channel 4 can be left disconnected The power is still voltage limited To increase the power specification a lower load impedance is necessary For example one channel into a 4 Ω load at 14 4 VDC can provide 28W at 10 THD By paralleling two channels one chan...

Page 18: ...im channel The harmonic crosstalk is most prevalent on channels that have the respective switching frequencies 90 degrees out of phase This situation arises on alternate channels of the TAS54x4C devices when the default switching phase of 45 degrees between adjacent channels is selected With this default phase setting the pairings of channels 1 and 3 and of channels 2 and 4 exhibits the most notic...

Page 19: ...rrect data 2 Switch to 180 phase difference The amount of cross talk and feedback from other channels are reduced These options can be incorporated individually or together Therefore the best THD N versus frequency data would be to incorporate all of the options at once for example ƒs 357K HZ at 180 phase shift Figure 9 shows a graphical representation of these options V PVDD 14 4 V RL 4 Ω PO 1 W ...

Page 20: ... be controlled before the output stage proceeds to the hi Z mode The low low mode pulls the output stage to ground to drain the stored current Load diagnostics mode The output stage in this mode is controlled internally through special states to measure the condition of the external amplifier load Gain and common mode ramps In addition to the five operating modes for each H Bridge output stage the...

Page 21: ...turn from load diagnostics The device must be powered on and the STANDBY pin must be pulled high before sending I2 C commands to the device Once STANDBY has been pulled high the power on procedure takes approximately 300 µs Power on device STANDBY high www ti com TAS54x4C Software Design Guidelines 2 2 Power Up and Initialization Every time the device is powered up or returns from a POR power on r...

Page 22: ...n MUTE mode The device starts in hi Z mode TAS54x4C Software Design Guidelines www ti com 2 3 Using the Device to Play Music The device is now powered on load diagnostics may have run and the device is configured The output stages are in hi Z mode The output stages must transition from hi Z mode to mute mode and then into play mode to minimize pops or clicks in the speakers The register values sho...

Page 23: ...s reached when register 0x05 is 0x0F www ti com TAS54x4C Software Design Guidelines 2 4 Using the Device to Stop Playing Musing The device requires one command to place all channels into hi Z mode from play mode The device still executes several ramps and transitions during the process as in Figure 12 If desired by the user the device can also be commanded to any state separately but this command ...

Page 24: ...st or can be run every time the audio system is turned on This test can also be run if a channel fault condition is detected In this case only the single channel can run while the other channels are still playing In this mode only a speaker wire shorts to battery and speaker wire shorts to ground are run but the flow is still the same The total time for load diagnostics is about 450 ms Load diagno...

Page 25: ...e the fault If the fault is not a global fault it is a channel fault See note B Optionally run load diagnostics Register 0x04 holds the status of the global faults These will clear when the fault clears When the value is 0x00 there are no faults present see note A Hi Z mode Any mode Hi Z mode www ti com TAS54x4C Software Design Guidelines 2 6 Fault Handling 2 6 1 Global Faults Global faults place ...

Page 26: ...i Z mode see note B From global fault handling Hi Z mode TAS54x4C Software Design Guidelines www ti com 2 6 2 Channel Faults Channel faults are faults that occur on an individual channel These faults are DC offset overcurrent and local overtemperature faults Only the channel that experienced the fault is placed in Hi Z The other channels remain playing The other difference between channel faults a...

Page 27: ...esponsible for compliance with all legal regulatory and safety related requirements concerning its products and any use of TI components in its applications notwithstanding any applications related information or support that may be provided by TI Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which anticipate dangerous consequences of failur...

Reviews: