TPA3156D2DAD

Product Folder Order Now Technical Documents Support & Community Tools & Software TPA3156D2 SLOS992 – DECEMBER 2017 TPA3156D2 2 x 70-W, Analog Input, Stereo, Class-D Audio Amplifier With Low Idle Power Dissipation 1 Features 3 Description • • • The TPA3156D2 has low idle power loss and helps to extend the battery life of Bluetooth/Wireless speakers and other battery-powered audio systems. The high efficiency of the TPA3156D2 device allows it to do 2 × 70 W with external heat sink on a dual layer PCB. This device integrates an efficiency boost mode, which dynamically reduces the current ripple of the external LC filter and the idle current . 1 • • • • • • • • 2 × 70 W Into a 4-Ω BTL Load at 24 V Wide Voltage Range: 4.5 V to 26 V Efficient Class-D Operation – Very Low Idle Current: 150°C Low Output high impedance Latched Too High DC Offset DC output voltage Low Output high impedance Latched Under Voltage on PVCC PVCC < 4.5V – Output high impedance Self-clearing Over Voltage on PVCC PVCC > 27V – Output high impedance Self-clearing 7.3.9 DC Detect Protection The TPA3156D2 has circuitry which will protect the speakers from DC current which might occur due to defective capacitors on the input or shorts on the printed circuit board at the inputs. A DC detect fault will be reported on the FAULT pin as a low state. The DC Detect fault will also cause the amplifier to shutdown by changing the state of the outputs to Hi-Z. If automatic recovery from the short circuit protection latch is desired, connect the FAULTZ pin directly to the SDZ pin. Connecting the FAULTZ and SDZ pins allows the FAULTZ pin function to automatically drive the SDZ pin low which clears the DC Detect protection latch. A DC Detect Fault is issued when the output differential voltage of either channel exceeds DC protection threshold level for more than 640 ms at the same polarity. Table 5 below shows some examples of the typical DC Detect Protection threshold for several values of the supply voltage. The Detect Protection Threshold feature protects the speaker from large DC currents or AC currents less than 2 Hz. To avoid nuisance faults due to the DC detect circuit, hold the SD pin low at power-up until the signals at the inputs are stable. Also, take care to match the impedance seen at the positive and negative inputs to avoid nuisance DC detect faults. Table 5 lists the minimum output offset voltages required to trigger the DC detect. The outputs must remain at or above the voltage listed in the table for more than 640 ms to trigger the DC detect. Table 5. DC Detect Threshold PVCC (V) VOS - OUTPUT OFFSET VOLTAGE (V) 4.5 1.35 6 1.8 12 3.6 18 5.4 7.3.10 Short-Circuit Protection and Automatic Recovery Feature The TPA3156D2 has protection from over current conditions caused by a short circuit on the output stage. The short circuit protection fault is reported on the FAULTZ pin as a low state. The amplifier outputs are switched to a high impedance state when the short circuit protection latch is engaged. The latch can be cleared by cycling the SDZ pin through the low state. If automatic recovery from the short circuit protection latch is desired, connect the FAULTZ pin directly to the SDZ pin. Connecting the FAULTZ and SDZ pins allows the FAULTZ pin function to automatically drive the SDZ pin low which clears the short-circuit protection latch. 7.3.11 Thermal Protection Thermal protection on the TPA3156D2 prevents damage to the device when the internal die temperature exceeds 150°C. This trip point has a ±15°C tolerance from device to device. Once the die temperature exceeds the thermal trip point, the device enters into the shutdown state and the outputs are disabled. This is a latched fault. Thermal protection faults are reported on the FAULTZ terminal as a low state. If automatic recovery from the thermal protection latch is desired, connect the FAULTZ pin directly to the SDZ pin. This allows the FAULTZ pin function to automatically drive the SDZ pin low which clears the thermal protection latch. Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: TPA3156D2 17 TPA3156D2 SLOS992 – DECEMBER 2017 www.ti.com 7.3.12 Device Modulation Scheme The TPA3156D2 and have the option of running in either BD modulation or low idle-loss mode. 7.3.12.1 BD-Modulation This is a modulation scheme that allows operation without the classic LC reconstruction filter when the amp is driving an inductive load with short speaker wires. Each output is switching from 0 volts to the supply voltage. The OUTPx and OUTNx are in phase with each other with no input so that there is little or no current in the speaker. The duty cycle of OUTPx is greater than 50% and OUTNx is less than 50% for positive output voltages. The duty cycle of OUTPx is less than 50% and OUTNx is greater than 50% for negative output voltages. The voltage across the load sits at 0V throughout most of the switching period, reducing the switching current, which reduces any I2R losses in the load. OUTP OUTN No Output OUTP- OUTN 0V Speaker Current OUTP OUTN Positive Output PVCC OUTP-OUTN 0V Speaker Current 0A OUTP Negative Output OUTN OUTP - OUTN 0V - PVCC Speaker Current 0A Figure 28. BD Mode Modulation 18 Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: TPA3156D2 TPA3156D2 www.ti.com SLOS992 – DECEMBER 2017 7.3.13 Efficiency: LC Filter Required with the Traditional Class-D Modulation Scheme The main reason that the traditional class-D amplifier-based on AD modulation requires an output filter is that the switching waveform results in maximum current flow. This causes more loss in the load, which causes lower efficiency. The ripple current is large for the traditional modulation scheme, because the ripple current is proportional to voltage multiplied by the time at that voltage. The differential voltage swing is 2 × VCC, and the time at each voltage is half the period for the traditional modulation scheme. An ideal LC filter is required to store the ripple current from each half cycle for the next half cycle, while any resistance causes power dissipation. The speaker is both resistive and reactive, whereas an LC filter is almost purely reactive. The TPA3156D2 and modulation schemes have little loss in the load without a filter because the pulses are short and the change in voltage is VCC instead of 2 × VCC. As the output power increases, the pulses widen, making the ripple current larger. Ripple current could be filtered with an LC filter for increased efficiency, but for most applications the filter is not required. An LC filter with a cutoff frequency less than the class-D switching frequency allows the switching current to flow through the filter instead of the load. The filter has less resistance but higher impedance at the switching frequency than the speaker, which results in less power dissipation, therefore increasing efficiency. 7.3.14 Ferrite Bead Filter Considerations Using the Advanced Emissions Suppression Technology in the TPA3156D2 and amplifiers, a high efficiency class-D audio amplifier can be designed while minimizing interference to surrounding circuits. Designing the amplifier can also be accomplished with only a low-cost ferrite bead filter. In this case the user must carefully select the ferrite bead used in the filter. One important aspect of the ferrite bead selection is the type of material used in the ferrite bead. Not all ferrite material is alike, therefore the user must select a material that is effective in the 10-MHz to 100-MHz range which is key to the operation of the class-D amplifier. Many of the specifications regulating consumer electronics have emissions limits as low as 30 MHz. The ferrite bead filter should be used to block radiation in the 30-MHz and above range from appearing on the speaker wires and the power supply lines which are good antennas for these signals. The impedance of the ferrite bead can be used along with a small capacitor with a value in the range of 1000 pF to reduce the frequency spectrum of the signal to an acceptable level. For best performance, the resonant frequency of the ferrite bead/ capacitor filter should be less than 10 MHz. Also, the ferrite bead must be large enough to maintain its impedance at the peak currents expected for the amplifier. Some ferrite bead manufacturers specify the bead impedance at a variety of current levels. In this case the user can make sure the ferrite bead maintains an adequate amount of impedance at the peak current the amplifier will see. If these specifications are not available, the device can also estimate the bead current handling capability by measuring the resonant frequency of the filter output at low power and at maximum power. A change of resonant frequency of less than fifty percent under this condition is desirable. Examples of ferrite beads which have been tested and work well with the TPA3136D2 can be seen in the TPA3136D2EVM user guide SLOU444. A high quality ceramic capacitor is also required for the ferrite bead filter. A low ESR capacitor with good temperature and voltage characteristics will work best. Additional EMC improvements may be obtained by adding snubber networks from each of the class-D outputs to ground. Suggested values for a simple RC series snubber network would be 18 Ω in series with a 330 pF capacitor although design of the snubber network is specific to every application and must be designed taking into account the parasitic reactance of the printed circuit board as well as the audio amp. Take care to evaluate the stress on the component in the snubber network especially if the amp is running at high PVCC. Also, make sure the layout of the snubber network is tight and returns directly to the GND pins on the IC. Figure 29 and Figure 30 are TPA3156D2 EN55022 Radiated Emissions results uses TPA3156D2EVM with 8-Ω speakers. Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: TPA3156D2 19 TPA3156D2 SLOS992 – DECEMBER 2017 www.ti.com Figure 29. TPA3156D2 Radiated Emissions-Horizontal (PVCC=19V, PO=1W) Figure 30. TPA3156D2 Radiated Emissions-Vertical (PVCC=19V, PO=1W) 7.3.15 When to Use an Output Filter for EMI Suppression A complete LC reconstruction filter should be added in some circuit instances. These circumstances might occur if there are nearby circuits which are sensitive to noise. In these cases a classic second order Butterworth filter similar to those shown in the figures below can be used. Some systems have little power supply decoupling from the AC line but are also subject to line conducted interference (LCI) regulations. These include systems powered by "wall warts" and "power bricks." In these cases, LC reconstruction filters can be the lowest cost means to pass LCI tests. Common mode chokes using low frequency ferrite material can also be effective at preventing line conducted interference. 10 µH OUTP L1 C2 0.68 µF 4W-8W 10 µH OUTN L2 C3 0.68 µF Ferrite Chip Bead OUTP 1 nF 4W-8W Ferrite Chip Bead OUTN 1 nF Figure 31. Output Filters 7.3.16 AM Avoidance EMI Reduction Table 6. AM Frequencies US EUROPEAN AM FREQUENCY (kHz) AM FREQUENCY (kHz) SWITCHING FREQUENCY (kHz) AM2 AM1 AM0 0 0 1 0 1 0 0 0 0 0 0 1 0 1 0 0 0 0 522-540 540-917 540-914 500 917-1125 914-1122 600 (or 400) 1125-1375 1122-1373 500 1375-1547 20 1373-1548 600 (or 400) Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: TPA3156D2 TPA3156D2 www.ti.com SLOS992 – DECEMBER 2017 Table 6. AM Frequencies (continued) US EUROPEAN AM FREQUENCY (kHz) AM FREQUENCY (kHz) 1547-1700 1548-1701 SWITCHING FREQUENCY (kHz) AM2 AM1 AM0 0 1 0 0 0 1 600 (or 500) 7.4 Device Functional Modes 7.4.1 PBTL Mode The TPA3156D2 can be connected in PBTL mode enabling up to 100W output power. This is done by: • Connect INPL and INNL directly to Ground (without capacitors) this sets the device in Mono mode during power up. • Connect OUTPR and OUTNR together for the positive speaker terminal and OUTNL and OUTPL together for the negative pin. • Analog input signal is applied to INPR and INNR. PVCC TPA3156D2 TPA3126D2 TPA3128D2 TPA3129D2 RINP Audio RIGHT Source And Control RINN Power Supply 4.5V t 26V OUTPR OUTNR LINP PBTL DETECT LINN LC Filter OUTPL OUTNL Figure 32. PBTL Mode 7.4.2 Mono Mode (Single Channel Mode) The TPA3156D2 and can be connected in MONO mode to cut the idle power-loss nearly by half. This is done by: • Connect INPR and INNR directly to Ground (without capacitors) this sets the device in Mono mode during power up. • Connect OUTPL and OUTNL to speaker just like normal BTL mode. • Analog input signal is applied to INPL and INNL. Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: TPA3156D2 21 TPA3156D2 SLOS992 – DECEMBER 2017 www.ti.com Device Functional Modes (continued) RINP RIGHT RINN MONO DETECT TPA3156D2 TPA3126D2 TPA3128D2 TPA3129D2 Power Supply 4.5V t 26V OUTPR OUTNR LINP Audio Source And Control LEFT LINN OUTPL OUTNL LC Filter Figure 33. MONO Mode 22 Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: TPA3156D2 TPA3156D2 www.ti.com SLOS992 – DECEMBER 2017 8 Applications and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 8.1 Application Information This section describes a 2.1 Master and Slave application. The Master is configured as stereo outputs and the Slave is configured as mono PBTL output. 8.2 Typical Application A 2.1 solution, U1 TPA3156D2 in Master mode 400 kHz, BTL, gain if 26 dB, power limit not implemented. U2 in Slave, PBTL mode gain of 26 dB. Inputs are connected for differential inputs. 287387/&),/7(5 (0,&5&618%%(5 / & ,1B3B5,*+7 ,1B1B5,*+7  —) &  —)   & —) *1' ,1B3B/()7 ,1B1B/()7 5 N  5 N   & —) & —)  5  5 N 5 N 087(B/5  39&&    4 N  *1' 39&& 6'= 39&& )$8/7= %635 5,13 28735 5,11 3/,0,7 *9'' *$,16/9 *1' /,13 *1' /,11 28715 %615 *1' %63/ 2873/ *1' 087( 2871/ $0 %61/ $0 39&& $0 39&& 6