AN10436

AN10436 TDA8932B/33(B) Class-D audio amplifier Rev. 01 — 12 December 2007 Application note Document information Info Keywords Abstract Content Class-D amplifier, High efficiency, Switch mode amplifier, Flat TV. This application note describes a stereo Switched Mode Amplifier (SMA) for audio, based on either the TDA8932B or TDA8933(B) Class-D audio amplifier device of NXP Semiconductors, which has been designed for Flat TV applications. The TDA8932B device is the high-power version that delivers an output power of 2 × 10 WRMS to 2 × 25 WRMS in a Single Ended (SE) configuration or 10 WRMS to 50 WRMS in a Bridge Tied Load (BTL) configuration. The TDA8933(B) device is the low-power version that delivers an output power of 2 × 5 WRMS to 2 × 15 WRMS in a SE configuration or 10 WRMS to 30 WRMS in a BTL configuration. This high efficiency SMA device has been designed to operate without a heat sink and has the flexibility to operate from either an asymmetrical supply or a symmetrical supply with a wide range (10 V to 36 V or ±5 V to ±18 V). The TDA8932B/33(B) device utilizes two advanced features, the Thermal Foldback (TF) and the cycle-by-cycle current limiting to avoid audio holes (interruptions) during normal operation. In addition, the TDA8932B/33(B) utilizes integrated Half Supply Voltage (HVP) buffers to simplify the design for an asymmetrical supply in the SE configuration. Control logic is integrated for a pop free transition between on/off. A SLEEP mode is incorporated to comply with the power saving regulations. An application designed around the TDA8932B/33(B) device is very robust because of the internal protection features, such as a number of voltage protections, OverCurrent Protection (OCP) and OverTemperature Protection (OTP). NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier Revision history Rev 01.00 Date 20071212 Description First release Contact information For additional information, please visit: http://www.nxp.com For sales office addresses, please send an email to: salesaddresses@nxp.com AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 2 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 1. Introduction This application note describes a reference design of a Switched Mode Amplifier (SMA) for audio, based on the TDA8932B or TDA8933(B) device of NXP Semiconductors operating from an asymmetrical supply. The TDA8932B device and the TDA8933(B) device are pin-to-pin compatible and can be used in either a stereo SE configuration or a mono BTL configuration. The TDA8932B is the high-power version and the TDA8933(B) is the low-power version. Together they cover a wide power range per channel of 5 WRMS to 50 WRMS. The two versions are available in the SO32 package (TDA8932BT, TDA8933T) and the HTSSOP32 package (TDA8932BTW, TDA8933BTW). The TDA8932B/33(B) Class-D amplifier is intended for: • • • • • Flat TV application Flat panel monitors Multimedia systems, docking stations Wireless speakers Microsystems Distinctive features • High efficiency Class-D audio amplifier due to a low RDSon in SE configuration. • Operates from a wide voltage range 10 V to 36 V (asymmetrical) or ±5 V to ±18 V (symmetrical). • Maximum power capability: – TDA8932B is 2 × 30 WRMS short time output power in 4 Ω SE without heat sink. – TDA8933(B) is 2 × 20 WRMS short time output power in 8 Ω SE without heat sink. • Cycle-by-cycle current limiting to avoid interruption during normal operation. • Unique Thermal Foldback (TF) to avoid interruption during normal operation. • Integrated Half Supply Voltage (HVP) buffers for reference and SE output capacitance (asymmetrical supply). • Internal logic for pop free power supply on/off cycling. • Low standby current in SLEEP mode for power saving regulations. Protection features • • • • • • • Window Protection (WP) UnderVoltage Protection (UVP) OverVoltage Protection (OVP) UnBalance Protection (UBP) OverCurrent Protection (OCP) OverTemperature Protection (OTP) ESD protection These features enable an engineer to design a high performance, reliable and cost effective SMA with only a small number of external components. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 3 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 1.1 Block diagram OSCREF OSCIO VDDA 8 28 OSCILLATOR DRIVER HIGH VSSD PWM MODULATOR CTRL DRIVER LOW 26 29 27 BOOT1 VDDP1 OUT1 VSSP1 10 31 IN1P 2 IN1N INREF IN2P 3 12 15 PWM MODULATOR 14 PROTECTIONS: OVP, OCP, OTP, UVP, TF, WP MANAGER 21 20 DRIVER HIGH CTRL DRIVER LOW 23 22 BOOT2 VDDP2 OUT2 VSSP2 IN2N VDDA STABILIZER 11 V 25 STAB1 DIAG 4 VDDA VSSP1 24 STABILIZER 11 V CGND 7 VSSP2 STAB2 POWERUP 6 REGULATOR 5 V MODE VSSD 18 DREF ENGAGE 5 VDDA 11 HVPREF 30 HVP1 TEST 13 TDA8932B VSSA 19 HVP2 HALF SUPPLY VOLTAGE 9 1, 16, 17, 32 001aaf597 VSSA VSSD(HW) Fig 1. Block diagram 1.2 Fixed frequency pulse width modulated Class-D concept The TDA8932B/33(B) device is a closed loop fixed frequency pulse width modulated Class-D amplifier with two differential analog inputs, each driving an independent power stage (see Figure 2). The power stage consists out of a low side and a high side N-channel MOSFET. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 4 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier The TDA8932B/33(B) can be configured for use in either SE or BTL. The major benefits of an SE configuration compared to a BTL configuration are cost and efficiency. This is because: • Only one pair of power switches is required for each channel. • Only one LP filter (inductor and film capacitor) is required for each channel. • Only two power stages for stereo in one package, therefore no heat sink required. TDA8932B/33(B) IN1P 2 3 IN1N IN2N 14 15 IN2P PWM 22 OUT2 LP FILTER CSE PWM 27 OUT1 LP FILTER CSE 010aaa000 Fig 2. TDA8932B/33(B) in SE configuration An internal feedback network has a fixed closed loop gain of 30 dB in the SE configuration (36 dB in the BTL configuration). The Pulse Width Modulation (PWM) output signal has a oscillator frequency that is fixed by either: • An internal oscillator when configured as master. • An external oscillator when configured as slave. The pulse width will be modulated according to the input signal. Section 3 describes the complete application design of the TDA8932B/33(B) and includes the dimensioning of the LP output filter. 1.3 Typical application circuits (simplified) 1.3.1 Asymmetrical supply stereo SE configuration The simplified application circuit of the TDA8932B/33(B) device when operated from an asymmetrical supply (single supply) can be seen in Figure 3. The TDA8932B/33(B) incorporates three integrated half supply voltage buffers to simplify the design for an asymmetrical supply in SE configuration. One buffer is for the reference decoupling capacitor (CHVPREF) on HVPREF (pin 11) and two other buffers are for the two AC-couple capacitors (CSE) in series with the speaker. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 5 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier VP Rvdda VP 10 Ω VPA Cvdda 100 nF Cvddp 220 μF (35 V) GND VSSD(HW) Cin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 32 31 30 29 28 27 26 VSSD(HW) OSCIO HVP1 VDDP1 BOOT1 OUT1 VSSP1 HVP1 Clc Cstab 100 nF Llc Cbo (1) 15 nF Rsn 10 Ω Cse (1) Cvssp 100 nF Cvddp 100 nF + − 470 nF Cin 470 nF IN1P IN1N DIAG ENGAGE Cen 470 nF HVP1 Csn 470 pF VP Cbo 15 nF MUTE control Rsn 10 Ω Llc POWERUP CGND SLEEP control Cosc 100 nF Rosc 39 kΩ Chvpref 47 μF (25 V) Chvp 100 nF Cinref 100 nF Cin VPA VDDA VSSA OSCREF HVPREF INREF TEST IN2N STAB1 U1 25 TDA8932B/ STAB2 24 33(B) 23 22 21 20 19 18 17 VSSP2 OUT2 BOOT2 VDDP2 HVP2 DREF VSSD(HW) VP Cvddp 100 nF Csn 470 pF HVP2 Clc Cse + − 470 nF Cin 470 nF IN2P VSSD(HW) Cdref 100 nF CHVP 100 nF HVP2 010aaa418 (1) The TDA8933T device requires a 1 MΩ resistor in parallel with the bootstrap capacitor Cbo. TDA8932BT, TDA8932BTW and TDA8933BTW devices do not require a 1 MΩ resistor. Fig 3. Simplified SE application TDA8932B/33(B) (asymmetrical supply) 1.3.2 Symmetrical supply stereo SE configuration The TDA8932B/33(B) can operate also from a symmetrical supply (see Figure 4). The three half supply voltage buffers are disabled. HVPREF (Pin 11), HVP1 (pin 30) and HVP2 (pin 19) should be connected to ground when supplied from a symmetrical supply. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 6 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier VDD Rvdda VDD 10 Ω VDDA Cvdda 100 nF Cvddp 220 μF (25 V) Cvssp 220 μF (25 V) GND Cvssa 100 nF Rvssa VSS 10 Ω VSSA VSS VSSD(HW) VSSA 1 Cin 32 31 30 29 28 27 26 VSSD(HW) OSCIO HVP1 VDDP1 BOOT1 OUT1 VSSP1 STAB1 Cstab 100 nF Cbo 15 nF VSSA VSS Cvssp 100 nF Csn 470 pF Rsn 10 Ω Llc + − 470 nF Cin 470 nF IN1P IN1N DIAG ENGAGE Cen 470 nF 2 3 4 5 6 7 8 9 10 11 12 Cvddp 100 nF VDD (1) MUTE control POWERUP CGND SLEEP control Cosc 100 nF Rosc 39 kΩ VSS Clc VDDA VSSA VDDA VSSA VSSA OSCREF HVPREF INREF 25 U1 TDA8932B/ STAB2 24 33(B) 23 22 21 20 19 18 17 VSSP2 OUT2 BOOT2 VDDP2 HVP2 DREF VSSD(HW) VSS Llc Cbo 15 nF (1) Cinref 100 nF VSSA TEST 13 Cin VDD Cvddp 100 nF Cdref 100 nF Rsn 10 Ω Csn 470 pF Cvssp 100 nF Clc + − 470 nF Cin 470 nF IN2N IN2P 14 15 VSSD(HW) 16 VSSA VSSA VSS 010aaa419 (1) The TDA8933T device requires a 1 MΩ resistor in parallel with the bootstrap capacitor Cbo. TDA8932BT, TDA8932BTW and TDA8933BTW devices do not require a 1 MΩ resistor. Fig 4. Simplified SE application TDA8932B/33(B) (symmetrical supply) A symmetrical supply has some benefits compared to an asymmetrical supply. First, the power bandwidth is not limited by the size of the SE capacitor. Therefore, for a full bandwidth (20 Hz to 20 kHz) amplifier, a symmetrical supply should be considered to avoid a large value SE capacitor. Secondly, when the supply is either unregulated and/or weak (e.g., a 50 Hz / 60 Hz transformer), the output signal will not suffer from asymmetrical clipping (see Section 4.4). 1.3.3 Asymmetrical supply mono BTL configuration The TDA8932B/33(B) can operate in BTL configuration when a high output power is required at a low supply voltage (e.g., for driving a subwoofer in a 2.1 system). See Figure 5. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 7 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier VP Rvdda VP 10 Ω VPA Cvdda 100 nF Cvddp 220 μF (35 V) GND VSSD(HW) Cin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 32 31 30 29 28 27 26 VSSD(HW) OSCIO HVP1 VDDP1 BOOT1 OUT1 VSSP1 STAB1 Rsn 10 Ω Csn 470 pF Cstab 100 nF Llc Cbo 15 nF (1) Rsn 10 Ω Clc Clc Cbo 15 nF (1) Chvp 100 nF Rhvp 470 Ω Cvddp 100 nF Csn 470 pF Rsn 10 Ω Llc + − Cin 470 nF 470 nF IN1P IN1N DIAG MUTE control SLEEP control Cosc 100 nF Rosc 39 kΩ HVPREF ENGAGE Cen 470 nF VP POWERUP CGND VPA VDDA VSSA OSCREF HVPREF INREF 25 U1 TDA8932B/ STAB2 24 33(B) 23 22 21 20 19 18 17 VSSP2 OUT2 BOOT2 VDDP2 HVP2 DREF VSSD(HW) HVPREF Chvp 100 nF Cinref 100 nF TEST IN2N IN2P VP Cvddp 100 nF Rhvp Cdref 100 nF Chvp 470 Ω 100 nF Csn 470 pF HVPREF VSSD(HW) 010aaa420 (1) The TDA8933T device requires a 1 MΩ resistor in parallel with the bootstrap capacitor Cbo. TDA8932BT, TDA8932BTW and TDA8933BTW devices do not require a 1 MΩ resistor. Fig 5. Simplified BTL application TDA8932B/33(B) (asymmetrical supply) 1.3.4 Symmetrical supply mono BTL configuration The TDA8932B/33(B) can operate in BTL configuration when high output powers are required at a low supply voltage (e.g., for driving a subwoofer in a 2.1 system). See Figure 6. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 8 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier VDD Rvdda VDD 10 Ω VDDA Cvdda 100 nF Cvddp 220 μF (25 V) Cvssp 220 μF (25 V) GND Cvssa 100 nF Rvssa VSS 10 Ω VSSA VSS VSSA Cin VSSD(HW) IN1P IN1N DIAG 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 32 31 30 29 28 27 26 25 VSSD(HW) OSCIO HVP1 VDDP1 BOOT1 OUT1 VSSP1 STAB1 Cbo 15 nF VSSA VSS Cvssp 100 nF Csn 470 pF Rsn 10 Ω Llc + Cin − 1 μF 1 μF Cvddp 100 nF VDD (1) MUTE control SLEEP control ENGAGE Cen 470 nF POWERUP CGND VSS Cosc 100 nF Rosc VDDA VSSA VDDA VSSA Clc VSSA OSCREF HVPREF INREF Cinref 100 nF U1 TDA8932B/ STAB2 24 33(B) 23 22 21 20 19 18 17 VSSP2 OUT2 BOOT2 VDDP2 HVP2 DREF VSSD(HW) Cstab 100 nF 39 kΩ VSS Llc Clc Cbo 15 nF (1) VSSA TEST IN2N IN2P VDD Cvddp 100 nF Cdref 100 nF Rsn 10 Ω Csn 470 pF Cvssp 100 nF VSSA VSSD(HW) VSSA VSS 010aaa421 (1) The TDA8933T device requires a 1 MΩ resistor in parallel with the bootstrap capacitor Cbo. TDA8932BT, TDA8932BTW and TDA8933BTW devices do not require a 1 MΩ resistor. Fig 6. Simplified BTL application TDA8932B/33(B) (symmetrical supply) 2. Functional IC description This chapter briefly describes the main functionality of the TDA8932B/33(B) device and the different modes. It also describes the different features and the protections implemented in the TDA8932B/33(B). Table 3 in Section 2.8 in gives a description of each pin. 2.1 Control inputs The TDA8932B/33(B) is controlled by two inputs, POWERUP (pin 6) and ENGAGE (pin 5). The POWERUP is a two-level high impedance input. The ENGAGE input has an internal pull-up current source and an internal pull-down resistor of 100 kΩ (typical). The internal pull-up current source is enabled after the power stages are AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 9 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier enabled. The DIAG pin is an I/O indicating FAULT mode and it can be used to switch the amplifier in FAULT mode by means of an external pull-down to CGND. The DIAG has an internal pull-up current source. Table 1. Mode 1) SLEEP 2) MUTE 3) OPERATING 4) FAULT [1] [2] Control voltages referenced to CGND VPOWERUP (V) < 0.8 >2 >2 >2 VENGAGE (V) < 0.8 < 0.8 > 2.4[1] Does not matter VDIAG (V) Does not matter > 2[2] > 2[2] < 0.8 ENGAGE open pin voltage is 2.8 V in OPERATING mode. DIAG open pin voltage is 2.5 V in MUTE and OPERATING mode. See Section 3.3 for the recommended control circuitry of the POWERUP, ENGAGE and DIAG. Remark: Do not use an external pull-up resistor at the ENGAGE input, as it has its own internal pull-up current source. 2.1.1 Mode description • SLEEP mode: The SLEEP mode is incorporated to reduce the power consumption in system idle mode. In SLEEP mode, the internal 5 V stabilizer (DREF), the 11 V stabilizers (STAB1, STAB2) and the half supply voltage buffers (HVPREF, HVP1, HVP2) are disabled to reduce supply current consumption. • MUTE mode: In MUTE mode, the 5 V (DREF) and the 11 V (STAB1, STAB2) stabilizers will be enabled (internal logic biased) and the half supply voltage buffers will charge respectively the reference decouple capacitor (CHVPREF) and the AC-couple capacitors (CSE) in series with the speaker. The power stage is enabled (starts switching) after the SE capacitors are charged completely. • OPERATING mode: In the OPERATING mode, the gain of the device is increased gradually to 30 dB per output stage to avoid pop noise. The complete start-up sequence will take about 500 ms in a typical SE application. • FAULT mode: The FAULT mode is entered when one of the internal protections is triggered (see Section 2.6) and as a consequence the DIAG (pin 4) is set to low. The internal pull-up current source of the ENGAGE pin is disabled in FAULT mode. Therefore, the external capacitor will be discharged by means of the internal pull-down resistor. The FAULT mode can be entered also by means of an external pull-down to CGND. Table 2 shows an overview of the internal protections. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 10 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 2.2 Half Supply Voltage (HVP) chargers The internal HVPREF, HVP1 and HVP2 buffers will quickly charge the reference capacitor (CHVPREF) and the SE capacitors (CSE) before the power stage is enabled. The typical charge current of the HVP1 (pin 30) and the HVP2 (pin 19) buffers is 80 mA (dependent on the junction temperature). The charge time of the SE capacitor can be estimated as follows: C SE ⋅ 0.5 ⋅ ( V DDA – V SSA ) t = ------------------------------------------------------------I Where: CSE = single ended capacitor (F) VDDA = analog supply voltage (V) VSSA = negative analog supply voltage (V) I = typical charge current (A) Example: Charging an SE capacitor of 1000 μF at a supply voltage of 22 V takes about 138 ms. Remark: The half supply voltage buffers are short circuit protected. (1) 2.3 Pop free power supply on/off cycling 2.3.1 Supply turn-on Internal logic will delay the operation (regardless of the control voltages) until the HVPREF, HVP1 and HVP2 buffers are settled at ½(VDDA − VSSA) to avoid pop noise. For an optimum pop performance, a capacitor of 470 nF should be attached to the ENGAGE (pin 5). This will make sure the gain and therefore the offset will be increased gradually to avoid pop sound (see Figure 21). 2.3.2 Supply turn-off Either the UnBalance Protection (UBP) or the UnderVoltage Protection (UVP) will avoid pop noise when the power supply is turned off. The power stage is disabled when either VDDA drops more than 20 % (see Section 2.6.6 for more detail) or the UVP threshold level (9.5 V typical) is reached. Remark: During power supply on/off cycling, an unwanted input signal from the audio source can still cause a pop noise. To prevent this the ENGAGE pin should be pulled down to CGND to mute any unwanted signal. 2.4 Oscillator frequency An external resistor connected between the OSCREF (pin 10) and VSSA sets the oscillator frequency of the PWM output. The oscillator frequency can be estimated with this equation: 9 f osc = 12.45 ⋅ 10 ------------------------R osc (2) AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 11 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier Where: Rosc = resistor to set the oscillator frequency. The oscillator frequency can be set between 250 kHz and 500 kHz. Example: The use of a 39 kΩ resistor will result in a oscillator frequency of about 320 kHz. Remark: A decouple capacitor of 100 nF should be connected across Rosc for noise reduction. Remark: Synchronization is recommended when two or more TDA8932B/33(B) devices are used in the same application (see Section 2.5). 2.5 Device synchronization Synchronization is recommended to avoid possible audible beat tones from the speakers when two or more TDA8932B/33(B) devices are used in the same application. Synchronization can be achieved by connecting all OSCIOs (pin 31) together and configuring one of the devices as master, while the other TDA8932B/33(B) device is configured as slave (see Figure 7). A device is configured as master when a resistor is connected between OSCREF (pin 10) and VSSA to set the oscillator frequency. The OSCIO (pin 31) of the master is then configured as an oscillator output for synchronization. The OSCREF (pin 10) of the slave devices should be shortened to VSSA to configure the OSCIO as an input. MASTER L/R CHANNEL SLAVE SUBWOOFER CHANNEL TDA8932B/33(B) TDA8932B/33(B) 9 VSSA VSSA Rosc 39 kΩ 10 OSCREF 31 OSCIO VSSA Cosc 100 nF 9 VSSA 10 OSCREF 31 OSCIO 010aaa001 Fig 7. Device synchronization in a 2.1 system Remark: In a 2.1 system, the SE device for the L/R channel should be configured as master. Remark: The maximum number of slaves driven by one master is 12. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 12 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 2.6 Limiting and protection features The TDA8932B/33(B) device utilizes two advanced limiting features, the thermal foldback and the cycle-by-cycle current limiting, to avoid audio holes (interruptions) during normal operation. In addition to these limiting features the device has several protection features that make the TDA8932B/33(B) very robust during a fault condition. The following protections are incorporated: • • • • • • Window Protection (WP) UnderVoltage Protections (UVP) OverVoltage Protection (OVP) UnBalance Protection (UBP) OverCurrent Protection (OCP) OverTemperature Protection (OTP) When one of the above protections is triggered, the device will enter the FAULT mode and the power stage is disabled immediately (floating). Furthermore, an internal timer of about 100 ms is started and the DIAG (pin 4), referenced to CGND, is set low for the first 50 ms of the timer to indicate this protection status (FAULT mode). In addition the internal pull-up current of the ENGAGE pin is disabled in the FAULT mode, so the external capacitor will be discharged by means of the internal pull-down resistor (100 kΩ). After about 100 ms the device will restart (self-recovering), but only when the fault condition has been resolved. A microcontroller can use the diagnostic signal (DIAG) to, e.g., shut down either the amplifier or the power supply. Table 2. Feature TF Overview of all the limiting and protection features inside the TDA8932B/33(B) Trigger level Min 140 °C Typ Max 150 °C DIAG output high Remark Unique thermal limiting to avoid audio holes when the junction temperature exceeds 140 °C during normal operation. (See Section 2.6.1) Unique current limiting to avoid audio holes when the current exceeds the trigger level during normal operation. (See Section 2.6.2) Power stage stays floating and entering FAULT mode. (See Section 2.6.3) Power stage becomes floating entering FAULT mode. (See Section 2.6.4) Power stage becomes floating entering FAULT mode. (See Section 2.6.5) Power stage becomes floating entering FAULT mode. (See Section 2.6.6) Cycle-by-cycle current limiting WP[1] UVP (VDDA − VSSA) OVP (VDDA − VSSA) UBP[3] TDA8932B 4.0 A 5.0 A 2.3 A 9.5 V 38.5 V 10 V 40 V high TDA8933(B) 2.0 A low level high level low level high level 7.6[1] 14.4[1] 8.0 V 36 V - low[2] low[2] low[2] low[2] 17.6 V[3] 29.3 V[3] - AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 13 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier Table 2. Feature Overview of all the limiting and protection features inside the TDA8932B/33(B) …continued Trigger level Min Typ 5.0 A 2.3 A Max 160 °C low[2] DIAG output low[2] Remark Power stage becomes floating entering FAULT mode. (See Section 2.6.7) Power stage becomes floating entering FAULT mode. (See Section 2.6.8) OCP TDA8932B 4.0 A Low ohmic short TDA8933(B) 2.0 A across the load OTP 155 °C [1] [2] [3] WP threshold level at VP = 22 V. See Equation 3 and Equation 4 for the threshold level versus the supply voltage. DIAG is active low for at least 50 ms. UBP threshold level at VP = 22 V. See Equation 5 and Equation 6 for the threshold level versus the supply voltage. 2.6.1 Thermal Foldback (TF) When the junction of the TDA8932B/33(B) exceeds 140 °C, the TF will gradually reduce the gain, limiting the power dissipation. This means that the device will not switch off, but will continue to operate at a slightly lower gain, causing no audio holes (interruptions). The maximum junction temperature will not go beyond the absolute maximum temperature. Therefore, a heat sink is not required and the thermal design becomes less critical and less temperature head room requires to be taken into account since audio holes will not occur and the device will always stay within the Safe Operating Area (SOA). 2.6.2 Cycle-by-cycle current limiting When the output current of the device exceeds either 4 A (TDA8932B) or 2 A (TDA8933(B)), the cycle-by-cycle current limitation becomes active. This means the device will not switch off, but continue to operate while limiting the current without causing audio holes (interruptions). The maximum output current will not go beyond the absolute maximum current. Remark: When the cycle-by-cycle current limiting becomes active, it will cause distortion. See Section 3.2 for information on how to calculate the peak output current, depending on the supply voltage and the speaker impedance. 2.6.3 Window Protection (WP) WP checks the voltage at the PWM outputs (OUT1 pin 27 and OUT2 pin 22) before the power stage is enabled (transition from SLEEP mode to MUTE / OPERATING mode). To avoid large currents flowing, the WP is activated (power stage stays floating) in the event of a short from the PWM output to either VDD or VSS. The DIAG is set to low for at least 50 ms. The PWM output voltage where the WP becomes active at an asymmetrical supply can be calculated as follows: Low threshold level: 11 V O ( wp ) l = ----- ⋅ V DDA 32 (3) AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 14 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier High threshold level: 21 V O ( wp ) h = ----- ⋅ V DDA 32 Where: VO(wp) = window protection output voltage (low or high). Referenced to VSSA (V). VDDA = analog supply voltage (V). The TDA8932B/33(B) will recover when the output voltage at OUT1 and OUT2 is within (21/32) VDDA > Vo > (11/32) VDDA. (4) 2.6.4 UnderVoltage Protection (UVP) The TDA8932B/33(B) requires a minimum supply voltage for proper operation. When the supply voltage drops below the UVP threshold level of 9.5 V (typical VDDA − VSSA), the power stage becomes floating and the DIAG is set low for at least 50 ms. 2.6.5 OverVoltage Protection (OVP) An OVP is incorporated because an SE Class-D amplifier is able to increase the supply voltage when it is driven at low audio frequencies. This phenomenon is better known as "supply pumping" (see also Section 4.3). The OVP prevents that supply pumping exceeds the absolute maximum supply voltage rating of the TDA8932B/33(B). This is a protection against self-destruction. The OVP threshold level is an internal fixed level at 38.5 V (typical VDDA − VSSA). Beyond this OVP threshold level the power stage will become floating and the DIAG is set low for at least 50 ms. Remark: The OVP will neither prevent nor limit an overvoltage caused by the power supply. 2.6.6 UnBalance Protection (UBP) The UBP senses the supply voltage unbalance between the analog supply voltages VDDA and VSSA with respect to the HVPREF voltage at pin 11. The UBP is triggered when the unbalance exceeds a certain level to avoid improper biasing resulting in e.g. pop. The DIAG is set low and remains low for at least 50 ms. The supply voltage where the UBP becomes active with an asymmetrical supply can be estimated as follows: Low threshold level: 8 V P ( ubp ) l = -- ⋅ V HVPREF 5 High threshold level: 8 V P ( ubp ) h = -- ⋅ V HVPREF 3 Where: VP(ubp) = unbalance protection supply voltage (low and high). VDDA (pin 8) referenced to VSSA (V). AN10436_1 © NXP B.V. 2007. All rights reserved. (5) (6) Application note Rev. 01 — 12 December 2007 15 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier VHVPREF = half supply voltage reference (pin 11) referenced to VSSA (V) The TDA8932B/33(B) will recover when the supply voltage is within (8/5) VHVPREF > VP > (8/3) VHVPREF. The supply voltage at which the UBP becomes active with a symmetrical supply can be estimated as follows: Low threshold level: 3 V DDA ( ubp ) l = -- ⋅ V SSA 5 High threshold level: 5 V DDA ( ubp ) h = -- ⋅ V SSA 3 Where: VDDA(ubp) = unbalance protection analog supply voltage. VDDA (pin 8) referenced to VHVPREF (V), HVPREF is connected to GND. VSSA = negative analog supply voltage (pin 9) referenced to VHVPREF (V) Example asymmetrical supply (use Equation 5 and Equation 6): At a supply voltage of 22 V, the voltage on HVPREF is equal to VHVPREF = 11 V. The HVPREF voltage is buffered so the level will change only very slowly. When the supply voltage drops quickly (dV/dt > 4 V/s), the UBP is triggered below 17.6 V. When the supply voltage increases quickly, the UBP is triggered above 29.3 V. Remark: With either an unregulated or a weak power supply, it might happen that this UBP is triggered, e.g., because of a voltage drop during a transient from no load to full load condition. See Section 4.4 for more detail. (8) (7) 2.6.7 OverCurrent Protection (OCP) The OCP is activated only in a fault condition when the current exceeds 4 A (TDA8932B) or 2 A (TDA8933(B)) because of either a low ohmic short across the load or a low ohmic short from the demodulated output (after the inductor) to either VSS or VDD. The DIAG is set low for 50 ms and the internal timer of 100 ms is started. The timer or the WP will keep the power stage disabled for at least 100 ms. As long as the short remains across the load, this cycle will repeat. The average power dissipation in the TDA8932B/33(B) will be low because the short circuit current will flow only during a very small part of the timer cycle of 100 ms. When the current exceeds 4 A (TDA8932B) or 2 A (TDA8933(B)) during normal operation, only the cycle-by-cycle current limiting is active without causing any audio holes (interruptions). See also Section 2.6.2. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 16 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 2.6.8 OverTemperature Protection (OTP) The OTP is activated only in a fault condition when the junction temperature exceeds 155 °C (typical) e.g. during a short across the SE capacitor. The DIAG output is set low for at least 50 ms and an internal timer of 100 ms is started. The timer will keep the power stage disabled for at least 100 ms. When the junction temperature exceeds 140 °C during normal operation, the thermal foldback is active without causing any audio holes (interruptions). See also Section 2.6.1. 2.7 Pinning information VSSD(HW) IN1P IN1N DIAG ENGAGE POWERUP CGND VDDA VSSA 1 2 3 4 5 6 7 8 9 32 VSSD(HW) 31 OSCIO 30 HVP1 29 VDDP1 28 BOOT1 27 OUT1 26 VSSP1 25 STAB1 24 STAB2 23 VSSP2 22 OUT2 21 BOOT2 20 VDDP2 19 HVP2 18 DREF 17 VSSD(HW) 010aaa422 TDA8932BT TDA8933T OSCREF 10 HVPREF 11 INREF 12 TEST 13 IN2N 14 IN2P 15 VSSD(HW) 16 Fig 8. Pin configuration SO32 AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 17 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier VSSD(HW) IN1P IN1N DIAG ENGAGE POWERUP CGND VDDA VSSA 1 2 3 4 5 6 7 8 9 32 VSSD(HW) 31 OSCIO 30 HVP1 29 VDDP1 28 BOOT1 27 OUT1 26 VSSP1 25 STAB1 24 STAB2 23 VSSP2 22 OUT2 21 BOOT2 20 VDDP2 19 HVP2 18 DREF 17 VSSD(HW) 010aaa423 TDA8932BTW TDA8933BTW OSCREF 10 HVPREF 11 INREF 12 TEST 13 IN2N 14 IN2P 15 VSSD(HW) 16 Fig 9. Pin configuration HTSSOP32 2.8 Pin description Table 3. Symbol VSSD(HW) Pin description Pin 1, 16, 17, 32 2 3 4 5 6 7 8 9 10 11 12 13 14 15 18 Description Negative digital supply voltage and handle wafer connection (heat spreader). With an asymmetrical supply, the VSSD(HW) is connected to the supply ground. With a symmetrical supply, the VSSD(HW) is connected to the negative supply line, VSSA. Positive audio input for power stage 1. Negative audio input for power stage1. Input/output to indicate the FAULT mode. DIAG has an internal pull-up and should left floating when unused. Input with internal pull-up to switch between MUTE mode and OPERATING mode. Input to switch between SLEEP mode and MUTE mode. Control ground, reference for POWERUP, ENGAGE and DIAG. This CGND is connected to the supply ground. Positive analog supply voltage. Negative analog supply voltage. Input to set the frequency for the internal oscillator (master configuration). In slave configuration this pin should be connected to VSSA. Decoupling of the internal half supply voltage reference (asymmetrical supply). With a symmetrical supply, this pin should be connected to the CGND (supply ground). Decoupling for the input reference voltage. Test signal input for testing purpose only (leave floating or connect to VSSA). Negative audio input for power stage 2. Positive audio input for power stage 2. Decoupling of the internal 5 V regulator. IN1P IN1N DIAG ENGAGE POWERUP CGND VDDA VSSA OSCREF HVPREF INREF TEST IN2N IN2P DREF AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 18 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier Table 3. Symbol HVP2 VDDP2 BOOT2 OUT2 VSSP2 STAB2 STAB1 VSSP1 OUT1 BOOT1 VDDP1 HVP1 OSCIO Pin description Pin 19 20 21 22 23 24 25 26 27 28 29 30 31 Description Half supply voltage buffer for the SE capacitor of output 2 (asymmetrical supply). With a symmetrical supply, this pin should be connected to the CGND (supply ground). Positive supply voltage for the power stage 2. Bootstrap for the high-side driver, power stage 2. PWM output, power stage 2. Negative supply voltage for the power stage 2. Decoupling of the internal 11 V regulator for power stage 2. Decoupling of the internal 11 V regulator for power stage 1. Negative supply voltage for the power stage 1. PWM output, power stage 1. Bootstrap for the high-side driver, channel 1. Positive supply voltage for the power stage 1. Half supply voltage buffer for the SE capacitor of output 1 (asymmetrical supply). With a symmetrical supply, this pin should be connected to the CGND (supply ground). Oscillator input in the slave configuration or the oscillator output in the master configuration. Exposed die pad applicable to HTSSOP32 package only. The exposed die pad should be connected to VSSD(HW). Exposed die pad 3. Design 2 x 5 W - 25 W audio amplifier (asymmetrical supply) This chapter describes a stereo amplifier reference design that is based on the TDA8932BT or the TDA8933(B)T device of NXP Semiconductors (see the schematic Section 3.10). This low-cost stereo Single Ended (SE) amplifier design operates with an asymmetrical supply (10 V to 36 V). The TDA8932BT and the TDA8933(B)T devices are pin-to-pin compatible. The reference PCB, when mounted with TDA8932BT (high-power version), can deliver a continuous time output power of 2 × 15 WRMS into 4 Ω (VP = 22 V) without a heat sink. The maximum short time output power is equal to 2 × 25 WRMS into 4 Ω (VP = 29 V). The reference PCB, when mounted with TDA8933(B)T (low-power version), can deliver a continuous time output power of 2 × 15 WRMS into 8 Ω (VP = 31 V) without a heat sink. The maximum short time output power is equal to 2 × 18 WRMS into 8 Ω (VP = 34 V). This chapter shows the most important equations that can be used as a guideline for any design based on the TDA8932B/33(B). 3.1 Output power estimation The output power for the SE and the BTL configuration, just before clipping, can be estimated through the use of these equations: 2 RL ⎛ ⎛ --------------------------------------------------------- ⎞ ⋅ ( 1 – t ⎞ W ( min ) ⋅ f osc ) ⋅ V P⎠ ⎝ ⎝ R L + R DSon + R s + R ESR⎠ = ----------------------------------------------------------------------------------------------------------------------------------8 ⋅ RL SE: P o(0.5%) (9) AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 19 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 2 RL ⎛ ⎛ ---------------------------------------------------⎞ ⋅ ( 1 – t ⎞ W ( min ) ⋅ f osc ) ⋅ V P⎠ ⎝ ⎝ R L + 2 ⋅ ( R DSon + R s )⎠ = ---------------------------------------------------------------------------------------------------------------------------2 ⋅ RL BTL: P o(0.5%) Where: (10) VP = supply voltage (V) (VDDP − VSSP) RL = load impedance (Ω) RDSon = on-resistance power switch (Ω) Rs = series resistance output inductor (Ω) RESR = equivalent series resistance of SE capacitance (Ω) tW(min) = minimum pulse width (s) (80 ns typical) fosc = oscillator frequency (Hz) (320 kHz typical R7 = 39 kΩ) Remark: Equation 9 and Equation 10 are valid only when: Peak output current ≤ 4 A for TDA8932B (see Section 3.2). Peak output current ≤ 2 A for TDA8933(B). The output power at 10 % THD can be estimated as follows: P o(10%) = 1.25 ⋅ P o(0.5%) (11) 3.1.1 TDA8932B output power estimation Figure 10, Figure 11, Figure 12, and Figure 13 show the estimated output power for the TDA8932B at THD = 0.5 % and THD = 10 % as a function of the supply voltage for SE and BTL for different load impedances. 40 Po (W) 30 001aad768 40 Po (W) RL = 4 Ω 001aad769 RL = 4 Ω 30 6Ω 20 8Ω 6Ω 20 8Ω 10 10 0 10 20 30 VP (V) 40 0 10 20 30 VP (V) 40 a. THD+N = 0.5 % b. THD+N = 10 % Fig 10. SE output power as a function of supply voltage Fig 11. SE output power as a function of supply voltage AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 20 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier Remark: Figure 10 and Figure 11 are calculated with RDSon = 0.15 Ω (at Tj = 25 °C), Rs = 0.05 Ω, RESR = 0.05 Ω and IO(ocp) = 4.0 A (minimum). 001aad770 001aad771 80 Po (W) 60 80 Po (W) RL = 8 Ω RL = 8 Ω 60 6Ω 6Ω 40 4Ω 20 20 40 4Ω 0 10 20 30 VP (V) 40 0 10 20 30 VP (V) 40 a. THD+N = 0.5 % b. THD+N = 10 % Fig 12. BTL output power as a function of supply voltage Fig 13. BTL output power as a function of supply voltage Remark: Figure 12 and Figure 13 are calculated with RDSon = 0.15 Ω (at Tj = 25 °C), Rs = 0.05 Ω and IO(ocp) = 4.0 A (minimum). The horizontal parts in the figures indicate the region where current limiting becomes active, when a level of 4.0 A (minimum) is taken into account. It is recommended to avoid these regions because current limiting will cause unwanted distortion (see Section 3.2). 3.1.2 TDA8933(B) output power estimation Figure 14, Figure 15, Figure 16, and Figure 17 show the estimated output power for the TDA8933(B) at THD = 0.5 % and THD = 10 % as a function of supply voltage for SE and BTL for different load impedances. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 21 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 20 Po (W) 15 010aaa105 20 Po (W) 15 010aaa108 RL = 8 Ω RL = 8 Ω 6Ω 10 6Ω 10 4Ω 4Ω 5 5 0 10 20 30 VP (V) 40 0 10 20 30 VP (V) 40 a. THD+N = 0.5 % b. THD+N = 10 % Fig 14. TDA8933(B): SE output power as a function of supply voltage Fig 15. TDA8933(B): SE output power as a function of supply voltage Remark: Figure 14 and Figure 15 are calculated with RDSon = 0.39 Ω (at Tj = 25 °C), Rs = 0.05 Ω, RESR = 0.05 Ω and IO(ocp) = 2.0 A (minimum). 010aaa106 010aaa107 20 Po (W) 15 RL = 6 Ω 10 20 Po (W) 15 RL = 6 Ω RL = 8 Ω RL = 8 Ω 10 5 5 0 10 12 14 16 18 VP (V) 20 0 10 12 14 16 18 VP (V) 20 a. THD+N = 0.5 % b. THD+N = 10 % Fig 16. TDA8933(B): BTL output power as a function of supply voltage Fig 17. TDA8933(B): BTL output power as a function of supply voltage Remark: Figure 16 and Figure 17 are calculated with RDSon = 0.39 Ω (at Tj = 25 °C), Rs = 0.05 Ω and IO(ocp) = 2.0 A (minimum). The horizontal parts in the figures indicate the region where current limiting becomes active when a level of 2.0 A (minimum) is taken into account. It is recommended to avoid these regions because current limiting will cause unwanted distortion (see Section 3.2). AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 22 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 3.2 Peak output current estimation The most important benefit of cycle-by-cycle current limiting is the loss of audio holes without requiring a lot of head room towards the maximum peak output current of the TDA8932B/33(B). The peak output current is limited internally above: • 4 A minimum for the TDA8932B. • 2 A minimum for the TDA8933(B). During normal operation, the output current should not exceed the threshold level of IO(ocp) = 4 A minimum (TDA8932B) or IO(ocp) = 2 A minimum (TDA8933(B)) because it will cause distortion. The peak output current in either SE or BTL can be estimated through the use of these equations: 0.5 ⋅ V P SE: I O ( peak ) ≤ --------------------------------------------------------R L + R DSon + R s + R ESR Vp BTL: I O ( peak ) ≤ --------------------------------------------------R L + 2 ⋅ ( R DSon + R s ) Where: VP = supply voltage (V) (VDDP-VSSP) RL = load impedance (Ω) RDSon = on-resistance power switch (Ω) Rs = series resistance output inductor (Ω) RESR = equivalent series resistance of SE capacitance (Ω) Example TDA8932B (IO(ocp) = 4 A minimum): A 4 Ω speaker in the SE configuration can be used until a supply voltage of 33 V (approx.) without running into current limiting. A 4 Ω speaker in the BTL configuration can be used until a supply voltage of 17.5 V (approx.) without running into current limiting. (12) (13) 3.3 Control circuit The recommended POWERUP circuit is a resistor divider between the supply voltage and CGND of the amplifier. Optionally a transistor can be used to enter SLEEP mode to reduce the power consumption in e.g., system idle mode. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 23 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 10 V .. 36 V OPTIONAL CIRCUIT FOR SLEEP CONTROL 47 kΩ 8 VDDA 6 POWERUP SLEEP OPERATING GND 12 kΩ 7 CGND 010aaa006 Fig 18. POWERUP circuit with optional sleep control Figure 19 and Figure 20 show two alternative POWERUP circuits to control SLEEP mode from a 3.3 V or 5 V logic supply by means of a micro controller. PUSH-PULL OUTPUT 3.3 V or 5 V OPEN-DRAIN OUTPUT 3.3 V or 5 V 10 kΩ 10 kΩ 6 POWERUP OPERATING 6 POWERUP OPERATING SLEEP 7 CGND SLEEP 7 CGND 010aaa007 010aaa008 Fig 19. Sleep control push-pull output Fig 20. Sleep control open-drain output Remark: Pull-up resistor should be ≥ 1 kΩ. An external capacitor of 470 nF is recommended at the ENGAGE pin. The switch in series with the internal pull-up current source will be closed after the power stage is enabled and finally the external capacitor will “softly” engage the amplifier. Softly means that the gain is gradually increased depending on the capacitor value (dV/dt) attached to the ENGAGE pin avoiding pop noise due to DC offset. 2.8 V OPTIONAL CIRCUIT FOR MUTE CONTROL 50 μA 5 ENGAGE SLEEP OPERATING GND 10 kΩ 470 nF 2 kΩ 100 kΩ 7 CGND 010aaa009 Fig 21. Engage circuit with optional mute control AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 24 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier Remark: Do not use an external pull-up resistor at the ENGAGE input. Remark: For a quick enable of the MUTE mode it is recommended to short circuit the 10 k series resistor. The DIAG pin can be used to: • Read out the status of respectively OPERATING mode or FAULT mode. • Quickly disable the power stage in case of fault conditions at set level. The internal pull-up current is limited (approx. 50 μA) therefore the maximum resistive load (referenced to CGND) is 47 kΩ. DIAG open pin voltage is 2.8 V (typ). The absolute maximum sink current of the DIAG pin should be limited to 5 mA (internal pull-down resistance Rpd ≈ 1 kΩ when set low). OPTIONAL CIRCUIT TO DISABLE POWER STAGE 2.5 V 50 μA 4 DIAG FAULT OPERATING ERROR 7 CGND 010aaa010 1 kΩ 100 kΩ GND Fig 22. DIAG circuit to disable power stage Remark: The DIAG should be left floating when unused. 3.4 Analog audio input The input signal is applied to the differential input of the TDA8932B/33(B) by means of AC-couple capacitors (see Figure 23). AC-couple capacitors are required for DC-blocking because the inputs (IN1P, IN1N, IN2P and IN2N) are biased at a voltage level of approximately +2.2 V (with respect to VSS) when operating from an asymmetrical supply. At symmetrical supply, the inputs are biased at a voltage level of approximately −2.2 V (with respect to HVPREF). The bias voltage is equal to the INREF voltage (pin 12). Remark: The input should be grounded close to the audio source (not at the amplifier side) to avoid a common ground with the power supply ground. R2 4.7 kΩ R3 4.7 kΩ C5 470 nF C7 470 nF IN1P 2 C6 330 pF Ri 100 kΩ IN1N 3 010aaa011 Fig 23. Input circuitry AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 25 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 3.4.1 Input impedance The input impedance of the TDA832B/33(B) device is equal to Ri = 100 kΩ. A low pass RC filter (R2, R3 and C6) is applied to reduce the sensitivity for out-of-band disturbances. 0 dB f−3dB(l) f−3dB(h) 010aaa012 Fig 24. Input transfer function The closed loop voltage gain at 1 kHz is equal to: Ri G v ( cl ) = 20 log ⎛ -------------------------------⎞ ⎝ R2 + R3 + R i⎠ The cut-off frequency of the low-pass filter is equal to: 1 f – 3dB ( h ) = --------------------------------------------------------( R2 + R3 ) ⋅ R i 2 π ⋅ ---------------------------------- ⋅ C6 R2 + R3 + R i The AC couple capacitors form a high-pass filter, with the total input impedance (R2 + R3 + Ri). The cut-off frequency of the high-pass filter is equal to: 1 f – 3dB ( l ) = ---------------------------------------------------------------------------⎛ C5 ⋅ C7⎞ 2 π ⋅ ( R2 + R3 + R i ) ⋅ -----------------⎝ C5 ⋅ C7⎠ Example: Substituting R2, R3 = 4.7 kΩ and the AC-couple capacitors of C5, C7 = 470 nF in Equation 16 results in a cut-off frequency of 6 Hz, well below 20 Hz. Substituting R2, R3 = 4.7 kΩ and C6 = 330 pF in Equation 15 results in a cut-off frequency of 56 kHz, well above 20 kHz. (16) (15) (14) 3.4.2 Gain reduction The gain of the TDA8932B/33(B) is fixed internally at 30 dB for SE configuration (or 36 dB BTL configuration). The gain can be reduced by a resistive voltage divider at the input (see Figure 25). AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 26 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier R2 4.7 kΩ R3 4.7 kΩ C5 470 nF C7 470 nF RP 22 kΩ IN1P 2 C6 330 pF Ri 100 kΩ IN1N 3 010aaa013 Fig 25. Resistive voltage divider at the input The closed-loop voltage gain Gv(cl) when applying a resistive divider can be calculated through the use of this equation: R EQ G v ( tot ) = G v ( cl ) + 20 log ⎛ -----------------------------------------⎞ ⎝ R EQ + ( R2 + R3 )⎠ Rp ⋅ Ri R EQ = ---------------Rp + Ri Where: REQ = equivalent resistance (Ω) Rp = parallel resistor (Ω) Ri = 100 kΩ internal input resistance (Ω) R2, R3 = series resistors (Ω) Gv(cl) = closed-loop voltage gain 30 dB for SE and 36 dB for BTL (dB) Example: Substituting R2 = R3 = 4.7 kΩ and RP = 22 kΩ in Equation 17 and Equation 18 results in a gain of Gv(tot) = 26.3 dB. Remark: Applying a parallel resistance to reduce the gain will affect the cut-off frequencies of the input circuitry. It is required to compensate for this when requiring a 20 Hz to 20 kHz bandwidth. (17) (18) 3.4.3 Reference decoupling (HVPREF) The HVPREF voltage (equal to ½(VDDA − VSSA)) is the reference for the output. The HVPREF is created internally by a resistor divider (2 × 90 kΩ) located between VDDA and VSSA. Proper decoupling with 47 μF and 100 nF is necessary to assure a good SVRR in the SE configuration. For the BTL configuration, there is a requirement only for a 100 nF capacitor since any ripple on the HVPREF is common for both output stages. 3.5 Speaker configuration and impedance For a flat frequency response (second order Butterworth filter), it is necessary to change the low pass filter components L2 / L3 and C14 / C23 according to the speaker configuration and impedance. See Figure 35 for more information. Table 4 shows the required component values for speaker impedances of 4 Ω, 6 Ω or 8 Ω. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 27 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier Filter component values Impedance (Ω) 4 6 8 L2 / L3 (μH) 22 33 47 10 15 22 C14 / C23 (nF) 680 470 330 1500 1000 680 Table 4. SE Configuration BTL 4 6 8 3.5.1 Filter inductor There are two main types of inductors: • Air coil, current independent inductance and no saturation effect. • Inductor with a magnetic core (ferrite or iron powder): – Magnetically unshielded version (pot core). – Magnetically shielded version (pot core or toroidal core). An air coil is used often in HiFi audio equipment, but is not very useful in mainstream audio because of the physical size. The major benefit of an unshielded inductor is cost. However, the magnetic stray field can cause either crosstalk issues or interference with other sensitive parts inside an audio or TV system (AM-receiver, picture interference, etc.). The benefit of the shielded magnetic inductor is that the magnetic field is captured inside the core, reducing the magnetic stray field. The most important parameters of an inductor are: • DC current rating to avoid magnetic saturation, causing an increase in audio distortion. • Linearity of the inductor, causing an increase in audio distortion (especially above 1 kHz). • DC resistance having a direct impact on efficiency. The DC current capability needs to be high enough to avoid magnetic saturation. High peak currents are a result of saturation because the inductor tends to acts like a short. Therefore, for a proper inductor selection it is important to consider the maximum current delivered by the amplifier, and the temperature of the inductor (higher inductor temperature will decrease the saturation level). The maximum current occurs at voltage clipping and can be calculated through the use of either Equation 12 for SE configuration or Equation 13 for BTL configuration. Example: For a 2 × 15 W SE amplifier operating at 22 V the maximum output current is equal to 2.1 A (RDSon = 0.15 Ω and Rs = 0.05 Ω and RESR = 0.06 Ω). Therefore, it is recommended to select an inductor that retains still at least 80 % of the nominal inductance at the maximum current of 2.1 A. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 28 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier Remark: Saturation will cause audio distortion and severe saturation might even damage the device. The inductor types listed below are recommended, based on audio and EMC performance. Table 5. Recommended inductor types L (μH) 22 47 22 47 22 47 22 47 22 47 Isat (A) 4.9 3.4 2.21 1.60 2.0 1.4 3.4 2.3 2.6 1.8 15 25 10 15 Output power (W per channel) in RL = 4 Ω 25 Brand and type TOKO 16RHBP leaded, shielded TOKO 11RHBP A7503CY leaded, shielded TOKO DS86C B992AS SMD, shielded Sagami 7311NA leaded, shielded Sagami 7E08N SMD, shielded Remark: For EMC purposes, it is important that the inner layer (for a multiple layer winding) is attached to the switching output to minimize electrical stray fields. The inner layer (start of the winding) is indicated with a dot mark on the inductor. In this way the outside layer acts like an electrical shielding for the inner layer attached to the output with fast alternating voltages. 3.5.2 Filter capacitor A film capacitor is the best choice for audio performance. However, in most cases a ceramic SMD capacitor (NPO or X7R) will also give a satisfying performance. The voltage rating of the filter capacitor should be 25 % higher than the maximum supply voltage VP in an asymmetrical application. In a symmetrical application the voltage rating should be 25 % higher than the half the maximum supply voltage (VDDP − VSSP). 3.5.3 Zobel damping network A zobel network is recommended in every Class-D amplifier application to damp the filter resonance (See in Figure 26 RZ and CZ). Filter resonance will occur due to the inductive behavior (LE) of the speaker voice coil. VDD PWM LLC CZ CLC RZ voice coil equivalent circuit RE LE VSS 010aaa426 Fig 26. Zobel damping network AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 29 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier This zobel damping network is quite effective for a voice coil inductance LE < 10 LLC. The zobel damping network will lower the resonance peak current in the filter inductor by at least 15 % to 40 % lowering the risk of unwanted inductor saturation. Remark: Besides inductor saturation a tweeter might also benefit from a zobel network since filter resonance can overstress the tweeter. Table 6 contains the optimum damping resistors for different capacitor values: Table 6. Damping resistors for different capacitor values Speaker impedance (Ω) Single ended 4 LLC (μH) 22 CLC (nF) 680 CZ (nF) 47 68 100 150 220 RZ (Ω) 82 56 39 27 22 Configuration A minimum zobel damping network CZ = 47 nF and RZ = 82 Ω is strongly recommended. The optimum damping resistors are equal for 6 Ω and 8 Ω speakers when using the filter component values from Table 4, which are calculated based on fo = 40 kHz. The resistor (RZ) should be able to at least dissipate the power when driving the amplifier with a 20 kHz unclipped sine wave. Figure 27 shows the sine wave power dissipation (20 kHz) as a function of supply voltage. 2.5 P (W) 2 010aaa427 (5) 1.5 (4) 1 (3) (2) 0.5 (1) 0 10 18 26 VP (V) 36 (1) CZ = 47 nF / RZ = 82 Ω (2) CZ = 68 nF / RZ = 56 Ω (3) CZ = 100 nF / RZ = 39 Ω (4) CZ = 150 nF / RZ = 27 Ω (5) CZ = 220 nF / RZ = 22 Ω Fig 27. Power dissipation as a function of supply voltage AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 30 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier Remark: If the amplifier is driven at the resonance frequency (fo = 40 kHz) of the filter, the power dissipation in the resistor will rise causing the resistor to overheat. 3.5.4 Voltage clamp diodes For a voice coil inductance LE greater than 10 times the filter inductance (LLC) the effectiveness of the zobel damping network is limited and the power dissipation in the resistor grows high, requiring bulky power resistors. In general, mostly subwoofer voice coils and HIFI multi-way speakers have such a high inductance. Remark: Applications for which the end user is able to disconnect the speaker and operate the amplifier without speaker, might also suffer from issues of robustness because of the inductor saturation. To avoid inductor saturation in case of high inductive load or no load, it is recommended to apply voltage clamp diodes at the output to the supply rails (see Figure 28). Dcl2 VDD PWM LLC CZ CLC Dcl1 RZ voice coil equivalent circuit RE LE VSS 010aaa428 Fig 28. Voltage clamp diodes Relatively cheap general purpose diodes, like the 1N4001 (VR = 50 V) or the 1N4002 (VR = 100 V) can be used for this purpose. The reverse voltage of the diode should be at least 1.2 times the supply voltage and the repetitive peak current should be 1.2 times the maximum current of the amplifier. 3.6 Single ended capacitor A single ended amplifier (Class-AB or Class-D) operating at an asymmetrical supply voltage will require an AC couple capacitor (SE capacitor) in series with the speaker. Especially for a low output power (< 25 W) it is a very cost effective solution compared to a BTL configuration. It should be noted, the SE capacitor has no major drawback on THD and audio performance in general. The SE capacitor forms a high-pass filter with the speaker impedance. Therefore, the frequency response will roll off with 20 dB per decade below the cut-off frequency f−3dB. The cut-off frequency is equal to: 1 f – 3dB = ------------------------------2 π ⋅ R L ⋅ C15 Where: RL = load impedance (Ω). C15 (C24) = Single Ended capacitance (F) (see schematic Section 3.10). AN10436_1 © NXP B.V. 2007. All rights reserved. (19) Application note Rev. 01 — 12 December 2007 31 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier Table 7 shows the required SE capacitor values for a cut-off frequency of 60 Hz, 40 Hz and 20 Hz. Table 7. Values SE capacitor C15 / C24 (μF) f−3dB = 60 Hz 4 6 8 680 470 330 f−3dB = 40 Hz 1000 680 470 f−3dB = 20 Hz 2200 1500 1000 Impedance (Ω) 3.6.1 Voltage rating The voltage rating of the SE capacitor should be at least equal to the nominal supply voltage VP in the application. This because the voltage at the SE capacitor can be modulated heavily when the amplifier is driven at either a low frequency or during an overload (a short circuit across the load or to VP). In these situations the peak voltage at the SE capacitor can be almost equal to the supply voltage. 3.6.2 Lifetime The ambient temperature and the ripple current have the greatest effect on the lifetime of the aluminium electrolytic capacitors. For lifetime considerations the SE capacitance must be able to at least handle the ripple current that is equal to the load current at ¼ rated output power. Only ¼ of the rated output power is taken into account, because it is not likely that an audio amplifier is driven continuously at rated output power over a lifetime. The ripple current at ¼ Prated is equal to: 1 ⁄ 2 ⋅ VP 1 -I = -------------------- ⋅ -2 ⋅ RL 4 Where: RL = load impedance (Ω) VP = supply voltage (V) (VDDP − VSSP) Example: The ripple current of an amplifier that operates at 22 V with a 4 Ω load (Prated = 15 W) is approximately 486 mA. This ripple current can be used to determine the expected lifetime of the SE capacitor. Most general purpose electrolytic capacitors (85 °C type) are capable already of handling a 486 mA ripple current. Both the ripple current and the voltage rating must be considered to prevent the capacitor from failing. (20) 3.7 Bootstrap capacitor A 15 nF SMD capacitor (NPO or X7R) is required to drive the high side N-channel MOSFET. The bootstrap capacitor is charged by means of an internal diode between the STAB1 (pin 25) and the BOOT1 (pin 28) at the moment that the low side MOSFET is on. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 32 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier The voltage across the bootstrap capacitor is equal to VSTAB1 − VF (forward voltage drop internal diode). Therefore a voltage rating of 16 V is sufficient for the two bootstrap capacitors. Remark: Only the TDA8933T device requires a 1 MΩ across both bootstrap capacitors for discharging when the power stage becomes floating. 3.8 Output RC snubber network An RC snubber network (see schematic Section 3.10) reduces the voltage ringing at the power stage output (pin 22 and pin 27) after a voltage transition. A proper implementation of this RC snubber will improve the EMC performance (see Figure 33). The worst case power dissipation in the snubber resistor R5 (R12) is equal to: P = 1 ⁄ 2 ⋅ C9 ⋅ ( V P ) 2 ⋅ 2 ⋅ f osc Where: C9 (C29) = snubber capacitor (F) VP = supply voltage (V) (VDDP − VSSP) fosc = oscillator frequency (Hz) Example: Substituting C9 = 470 pF, VP = 22 V and fosc = 320 kHz in Equation 21, results in a power dissipation of 73 mW, requiring an 0805 SMD. The voltage rating of the snubber capacitors (C9 and C26) should be 25 % higher than the maximum supply voltage in the application. (21) 3.9 Layout recommendations The PCB design of an SMA is probably the most difficult part of the design, because it might affect the audio performance, the EMC performance, the thermal performance, or even the functionality of the TDA8932B/33(B). 3.9.1 EMC considerations A double-sided PCB with plated through holes and 35 μm copper is recommended, but a single layer is feasible as well. Figure 29 shows a proposed floor plan of the critical components that contribute to a good audio and EMC performance. The top side of this reference board is used to place the leaded components and the copper plane for thermal reasons. For more information on thermal considerations refer to Section 3.9.2. The bottom side of the double-layer PCB is used to place the SMD components, including the TDA8932B/33(B) and the majority of the signal tracks (see Figure 30 to Figure 33). AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 33 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier BUFFER CAPACITOR Large signal supply and output Small signal input U1 FILTER INDUCTOR L2 L3 C1 SE CAPACITOR C15 C24 FILTER CAPACITOR C14 C23 SOLID “CLEAN” GND Audio outputs Supply Audio inputs I/O CONNECTORS AT ONE SIDE TDA8932B/33(B) 010aaa056 Fig 29. Proposed floor plan of the components Some important notes for a proper layout are summarized below: • Input / output connectors at one side of the PCB (solid and "clean" star GND connection). • Supply buffer capacitor (C1) close to the IC. • Filter inductor (L2, L3) close to the IC. • Filter capacitor (C14, C23) close to the output connector, together with the SE capacitor (C15, C24). • Place the High Frequency (HF) supply decoupling capacitor close to the IC (see Figure 30). • • • • Place the HF decoupling capacitor STAB1/2 voltage close to the IC (see Figure 31). Place the Bootstrap capacitor of the high-side driver close to the IC (see Figure 32). Place the RC output snubber network close to the IC (see Figure 33). Place the HF decoupling capacitor DREF voltage close to the IC (see Figure 33). AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 34 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier C4 C10 R5 32 U1 1 R5 C4 C10 32 U1 1 29 C9 15 29 C9 15 26 C17 23 C25 20 C17 26 25 24 23 C25 R12 C18 C31 17 C30 16 C3 010aaa060 R12 C18 C31 17 C30 16 C3 010aaa061 Fig 30. HF decoupling supply C8, C25 Fig 31. HF decoupling STAB1/2 C17 C4 C10 R5 C9 15 32 U1 1 R5 C4 C10 32 U1 1 29 28 25 C17 C25 22 21 C9 15 29 26 C25 23 20 C17 R12 C18 C31 17 C30 16 C3 010aaa057 R12 C18 C31 17 C30 16 C3 010aaa058 Fig 32. Bootstrap capacitor high-side driver C10, C18 Fig 33. RC output snubber network C4 C10 R5 C9 15 32 U1 1 C17 C25 R12 C18 C31 18 17 C30 16 C3 010aaa059 Fig 34. HF decoupling DREF C30 Remark: SMD components are on the bottom layer, viewed from the top. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 35 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier In general: • Minimizing the current loops that carry fast alternating currents will reduce magnetic radiation. • Minimizing the length / size of the PWM output track (fast alternating voltages) as much as possible, will prevent capacitive coupling to the environment. Otherwise this could lead to disturbances of high impedance inputs. 3.9.2 Thermal considerations The thermal resistance is determined by the selected SMD package, the PCB layout implementation and the airflow inside the final enclosure of the amplifier. The TDA8932B/33(B) is available in two different thermally enhanced SMD packages: • TDA8932BT/33T in SO32 (SOT287-1) package for reflow and wave solder process. • TDA8932BTW/33BTW in an HTSSOP32 (SOT549-1) package for reflow solder process only. Thermal resistance SO32 package The SO32 package has special thermal corner leads, pins 1, 16, 17 and 32, increasing the power capability (reducing the overall Rth(j-a)) when soldered to a thermal copper plane at VSSA level. The SO package is very suitable for single layer PCB designs or PCB designs with limited space for a thermal plane. Due to the package size the SO32 is able to radiate a significant part of the heat directly into the air (thermal resistance is less depending on the heat transfer via the PCB). The thermal resistance of a S032 package will range from about 35 K/W to 50 K/W when mounted on a single or two layer PCB (free air natural convection). Mounting a heat sink can further decrease the thermal resistance with another 15 % to 25 %. The thermal resistance measured at the compact reference PCB (55 mm × 45 mm) with S032 package can be found in Section 5.3. Thermal resistance HTSSOP32 package The HTSSOP32 package has an exposed die-pad that only reduces the overall Rth(j-a) significantly when soldered to a thermal copper plane at VSSA level (thermal resistance is strongly depending on the size and the number of copper planes). This makes the HTSSOP package very suitable for multilayer PCB designs with sufficient space for two or three thermal copper planes. When applying three thermal copper planes it is even possible to reach a continuous time output power of 2 × 25 W without a heat sink. The thermal resistance of a HTSSOP32 package will range from about 25 K/W to 55 K/W when mounted on a multilayer PCB without heat sink (free air natural convection). Increasing the area of the thermal copper planes, the number of planes, or the copper thickness will further reduce the thermal resistance Rth(j-a) of both packages. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 36 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier Airflow inside enclosure At a set level the airflow inside the enclosure will be limited compared to the situation in free air natural convection. The airflow and other heat sources close to the amplifier will influence the temperature significantly. Therefore it is always recommended (and the responsibility of the set maker) to check the temperature behavior in the final environment of the amplifier. Remark: The TDA8932B/33(B) amplifier with the thermal foldback feature will never cause audio interruption (audio holes) due to the limited airflow and the limited presence of other heat sources close to the amplifier. Therefore this thermal foldback feature will improve the reliable of the amplifier application under extreme temperature conditions because the device itself will always stay within the Safe Operating Area (SOA). Thermal resistance Measured thermal resistance of both the SO32 and the HTSSOP32 reference design can be found in Section 5.3. Thermal via’s Thermal via’s should be applied for an optimum heat flow to other layers of the PCB to reduce the Rth(j−a). The thermal via’s should be placed close to corner leads and beyond the package for the SO32 package (see PCB layout Section 3.12). Remark: Do not use via’s with web construction, as they will have a high thermal resistance. Thermal calculations To estimate the maximum junction temperature, Equation 22 can be used: T j ( max ) ≈ T amb + R th ( j – a ) ⋅ P Where: Tamb = ambient temperature (°C) P = power dissipation in U1 (W) (see Figure 50 or Figure 61, P versus PO) Rth(j−a) = thermal resistance junction ambient (K/W) Example: Estimation of the junction temperature at Prated (for FTC requirements). Power dissipation P = 2.5 W (see Figure 47) at Prated = 2 × 15 W in 4 Ω. The estimated junction temperature at Tamb = 25 °C and Rth(j−a) = 44 K/W, will be Tj(max) = 135 °C (approx.) (Equation 22), staying below the TF threshold level of 140 °C. At a Prated = 2 × 25 W in 4 Ω the TF becomes active. The TF will gradually reduce the gain and therefore reduce the long-term output power. See Section 5.3 for the output power as a function of time, when the TF becomes active. The major benefit of the TF feature is that the amplifier is not switched off when it reaches the maximum junction temperature. Remark: Lifetime is guaranteed because the TDA8932B/33(B) stays within the safe operating area due to the TF feature. AN10436_1 © NXP B.V. 2007. All rights reserved. (22) Application note Rev. 01 — 12 December 2007 37 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier Remark: For thermal reliability and/or quality requirements on set level, an average music power of ¼ Prated is assumed. This assumption can be made because audio amplifiers are not driven continuously at the rated output power. Taking this into account, shows the major benefit of Class-D as compared to Class-AB. Class-D dissipates less at ¼ Prated and that makes it possible to comply easily with the thermal reliability and/or quality regulations with a cheap SO32 or HTSSOP32 package without a heat sink. 3.10 Schematic - revision 3.00 L1 BEAD R1 VP VPA C3 100 nF C1 220 μF/35 V J1 VP = 10V ...35V GND 1 2 10 Ω C2 220 μF/35 V 1 IN1 J2 R2 4.7 kΩ R3 4.7 kΩ C5 470 nF VSSD/HW IN1P IN1N DIAG ENGAGE POWERUP CGND VDDA VSSA VSSD/HW OSCIO HVP1 VDDP1 BOOT1 OUT1 VSSP1 32 31 30 29 28 27 26 25 C10 15 nF(1) C8 100 nF C9 470 pF R5 10 Ω L2 22 μH C12 100 nF R8 22 Ω C17 100 nF C14 680 nF C4 100 nF 2 C6 330 pF 3 HVP1 4 R4 10 kΩ 2 S2 1 47 kΩ C11 ON 470 nF SLEEP VP J3 1 2 + OUT1 − HVP1 C15 1000 μF, 25 V 4Ω 5 VPA R6 2 S1 1 R7 6 12 kΩ 7 8 9 10 11 OPERATING MUTE C16 100nF R10 39 kΩ VPA U1 STAB1 TDA8932BT 24 STAB2 /33T VSSP2 OUT2 BOOT2 VDDP2 HVP2 23 22 21 20 19 18 VSSD/HW 17 OSCREF HVPREF INREF TEST IN2N IN2P VSSD/HW J4 C18 15 nF(1) L3 22 μH R12 10 Ω C19 100 nF R13 22 Ω C23 680 nF C20 47 μF C21 100 nF C27 470 nF 12 C22 100 nF 13 1 2 − OUT2 + HVP2 4Ω VP C25 100 nF C26 470 pF R14 14 C28 330 pF 15 C24 1000 μF, 25 V IN2 J5 4.7 kΩ R15 4.7 kΩ C29 470 nF 16 C30 100 nF C31 100 nF HVP2 010aaa062 (1) The TDA8933T device requires a 1 MΩ in parallel with the bootstrap capacitor Cbo. Fig 35. Schematic - version 3.00 AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 38 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 3.11 Bill of materials - revision 3.00 Table 8. Item 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 2 10 5 2 2 2 2 2 2 1 1 3 2 1 2 3 5 1 1 1 2 1 2 1 Bill of materials Qty Reference C1, C2 Part 220 μF / 35 V Description General purpose 85 °C, Ø 8 mm SMD 0805, X7R SMD 1206, X7R SMD 0805, X7R SMD 1206, X7R SMD 0805, X7R SMD 0805, X7R MKT-02 General purpose 85 °C Ø 12.5 mm General purpose 85 °C Ø 6 mm 3 mm LED Camden Electronics CTB3551/2 SMD 1206, 742792115 / Würth Elektronik or BLM41PG600SN1L / Murata 11RHBP / Toko A7503CY-220M SMD 1206 SMD 0805 SMD 0805 SMD 0805 SMD 0805 SMD 2512 SMD 0805 090320901 / Secme SOT287-1 (SO32) / NXP Semiconductors SOT287-1 (SO32) / NXP Semiconductors C3, C4, C12, C16, C17, C19, 100 nF / 50 V C21, C22, C30, C31 C5, C7, C11, C27, C29 C6, C28 C8, C25 C26, C9 C10, C18 C23, C14 C24, C15 C20 D1 J1, J3, J4 J2, J5 L1 L3, L2 R1, R5, R12 R2, R3, R14, R15, R16 R4 R6 R7 R8, R13 R10 S2, S1 U1 470 nF / 16 V 330 pF / 16 V 100 nF / 50 V 470 pF / 50 V 15 nF / 16 V 680 nF / 63 V 1000 μF / 25 V 47 μF / 25 V LED Screw terminal Cinch Bead 22 μH 10 R 4.7 k 10 k 47 k 12 k 22 R 39 k PCB switch TDA8932BT TDA8933(B)T 3.12 PCB layout - Revision 2 Double-sided PCB (55 mm × 45 mm) with plated through holes (Ø = 0.6 mm), 35 μm copper and FR4 base material. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 39 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 010aaa078 Fig 36. Top view, copper and silk screen top 010aaa110 Fig 37. Top view, copper and silk screen bottom AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 40 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 4. Power supply 4.1 Supply filtering A CLC phi filter (C1, L1 and C2) is used to keep the High Frequency (HF) currents locally around the amplifier (see Figure 38). Two 100 nF SMD capacitors (C8 and C25) and an electrolytic buffer capacitor (C1) should be placed close to the amplifier to minimize the area of the HF current loops to avoid emission. The ferrite bead (L1) will avoid the flow of HF currents in (mostly) large supply voltage loops. The analog voltage (VDDA) of the TDA8932B/33(B) requires an RC filter of 10 Ω (R1) and 100 nF (C3) to avoid the HF noise entering the analog controller part of the device. VDDA pin 8 R1 10 ohm C3 TDA8932B/33(B) 29 HF CURRENTS 27 OUT 1 L1 FERRITE BEAD C2 C1 C8 POWER SUPPLY 26 LP FILTER C15 C25 23 22 OUT 2 20 LP FILTER C24 010aaa063 Fig 38. Supply filtering 4.1.1 Lifetime electrolytic capacitor The ambient temperature and the ripple current have the greatest effect on the lifetime of the aluminium electrolytic capacitors. The output power of an amplifier is assumed often to be ¼ of the total rated output power. At a power rating of 2 × 3.75 W (¼ × 15 W) the lifetime is not an issue when general-purpose electrolytic capacitors (with a value of at least 220 μF) are used. 4.2 Supply GND connection The best practice to avoid any common ground path with the power supply is to leave the supply floating. The power supply should be attached to GND at the amplifier side. The differential input should be grounded at the sound processor and not at the amplifier side. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 41 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier POWER SUPPLY SOUND PROCESSOR DIFFERENTIAL INPUT AMPLIFIER TDA8932B/33(B) DAC GND OUT SPEAKER GND FERRITE BEAD LP FILTER 100nF GND LEAVE FLOATING FROM GROUND (OR USE RC) STAR GROUND AMPLIFIER SIDE GND SOLID GROUND PLANE 010aaa079 Fig 39. Supply GND connection 4.3 Low frequency supply pumping effect A Single Ended (SE) Class-D amplifier will deliver energy back to the supply line (VP) during the negative part of the audio signal. Because most power supplies are not capable of sinking energy, the supply voltage will increase especially when driving the amplifier at low audio frequencies. This phenomenon is often called the pumping effect. The voltage increase caused by the pumping effect depends on: • • • • • The speaker impedance. The supply voltage. The audio signal frequency. The capacitance value of the supply line. The source/sink current of other channels (including the quiescent current of the amplifier). • The current drawn from other circuits attached to the same supply line. This voltage increase might trigger the OVP of the audio amplifier and/or cause incorrect control behavior of the regulated power supply. The most effective way to overcome the pumping effect in a stereo SE application is to apply one of the input signals to the negative input to invert the phase of that particular output (see Figure 40). AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 42 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier TDA8932B/33(B) IN1P 2 3 IN1N IN2N 14 15 IN2P 27 OUT1 LP FILTER C15 22 OUT2 LP FILTER C24 010aaa064 Fig 40. Inverting the phase of one output and input (of channel 2) With this method, OUT1 and OUT2 are out of phase to minimize the pumping effect. The inversion of one of the outputs will also halve the peak current drawn from the power supply at a low audio frequency. Remark: Do not forget to change the polarity of the speaker connection of channel 2 to get the original phase of the signal from the speaker. 4.4 Unregulated or weak power supply The voltage ripple of an unregulated power supply can be quite significant, due to: • The output impedance (load regulation). • A variation on the AC mains (line regulation). • A cross regulation in a multiple output SMPS. Therefore, when operating from an asymmetrical supply, this voltage ripple will cause asymmetrical clipping. This might trigger also the UBP (UnBalance Protection) when the voltage ripple exceeds either −20 % or +33 % of the nominal supply voltage (see also Section 2.6.6). Therefore, any unregulated power supply (an auxiliary voltage from either an SMPS or a 50 Hz / 60 Hz transformer) might need some attention to minimize the load, the line and the cross regulation. The voltage dip during a transient from no load condition to full load condition should be considered. The average supply current in full load for a stereo amplifier can be estimated as follows: 2 ⋅ Po SE: I P(avg) = ------------------η po ⋅ V P Po BTL: I P(avg) = ------------------η po ⋅ V P Where: Po = RMS output power per channel (W) ηpo = output power efficiency, audio amplifier AN10436_1 © NXP B.V. 2007. All rights reserved. (23) (24) Application note Rev. 01 — 12 December 2007 43 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier VP = supply voltage (V) (VDDP - VSSP) Example: A 2 × 15 W amplifier at 22 V and 89 % efficiency will draw an average supply current of 1.53 A. Remark: For either a 50 Hz / 60 Hz transformer or a weak auxiliary supply, it might be worthwhile to consider the use of a symmetrical supply to avoid asymmetrical clipping (early clipping of the positive output voltage). 5. Performance characterization TDA8932B 5.1 Audio characterization SE 5.1.1 Performance figures SE Table 9 shows the measured performance figures of the TDA8932BT two layer reference board (55 mm × 45 mm) configured in SE configuration. VP = 22 V, RL = 2 × 4 Ω SE, fosc = 320 kHz, fi = 1 kHz, Tamb = 25 °C unless specified otherwise. Table 9. VP Po(RMS) Performance figures Conditions / notes operates down to UVP threshold level operates up to OVP threshold level RMS output power Continuous time output power per channel RL = 4 Ω THD+N = 10 % THD+N = 0.5 % RL = 8 Ω, VP = 30 V THD+N = 10 % THD+N = 0.5 % short time output power RL = 4 Ω, VP = 29 V THD+N = 10 % THD+N = 0.5 % THD+N total harmonic Po = 1 W, AES17 brick wall filter 20 kHz distortion-plus-noise RL = 4 Ω RL = 8 Ω, VP = 30 V ηpo output power efficiency Po = 15 W RL = 4 Ω RL = 8 Ω, VP = 30 V Gv(cl) Vi(sens) closed-loop voltage gain input sensitivity voltage Vi = 100 mVRMS, 1 kHz, Ri = 4.7 kΩ, no load Prated = 2 × 15 W 15.3 12.1 15.5 12.3 26.5 21.1 0.015 0.01 92 93 29.2 305 W W W W W W % % % % dB mVRMS Min 10[1] Typ Max 36[1] Unit V supply voltage Symbol Parameters AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 44 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier Table 9. Vn(o) Performance figures …continued Conditions / notes OPERATING mode, inputs shorted at INP, INN Min Typ 70 100 98 40 - 45,000 62 60 80 680 53 Max Unit μV μV dB Hz dB dB dB μA mA noise output voltage MUTE mode Symbol Parameters S/N B SVRR Signal to Noise ratio unweighted, w.r.t. VO = 7.8 VRMS bandwidth ±3 dB, C15 = C24 = 1000 μF supply voltage ripple RL = 4 Ω, Vripple = 500 mVRMS, 100 Hz, inputs shorted rejection RL = 8 Ω, Vripple = 500 mVRMS, 100 Hz, inputs shorted αcs IP Iq [1] channel separation supply current quiescent current Po = 1 W, 1 kHz total application; SLEEP mode, no load total application; MUTE / OPERATING mode - It is not recommended to operate the IC at the supply boundaries (10 V or 36 V) unless the supply is regulated well. 5.1.2 Performance graphs SE 001aad772 001aad773 102 THD+N (%) 10 102 THD+N (%) 10 1 1 10−1 (1) (3) 10−1 (1) (3) 10−2 (2) 10−2 (2) 10−3 10−2 10−1 1 10 102 Po (W/channel) 10−3 10−2 10−1 1 10 102 Po (W/channel) VP = 22 V, 2 × 4 Ω SE (1) = 6 kHz (2) = 1 kHz (3) = 100 Hz VP = 30 V, 2 × 8 Ω SE (1) = 6 kHz (2) = 1 kHz (3) = 100 Hz Fig 41. THD+N as a function of output power Fig 42. THD+N as a function of output power AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 45 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 102 THD+N (%) 10 001aad774 102 THD+N (%) 10 001aad775 1 (1) (2) 1 (1) (2) 10−1 10−1 10−2 10−2 10−3 10 102 103 104 fi (Hz) 105 10−3 10 102 103 104 fi (Hz) 105 VP = 22 V, 2 × 4 Ω SE (1) = 10 W (2) = 1 W VP = 30 V, 2 × 8 Ω SE (1) = 10 W (2) = 1 W Fig 43. THD+N as a function of frequency Fig 44. THD+N as a function of frequency 40 Gv (dB) 30 001aad776 0 SVRR (dB) −20 001aad777 −40 (2) (1) −60 (2) (1) 20 −80 10 10 102 103 104 fi (Hz) 105 −100 10 102 103 104 fi (Hz) 105 Vi = 100 mVRMS, Ri = 0 Ω, CSE = 1000 μF (1) 2 × 4 Ω SE @ VP = 22 V (2) 2 × 8 Ω SE @ VP = 30 V Vripple = 500 mVRMS w.r.t. GND, shorted input Ri = 0 Ω (1) = 2 × 4 Ω SE @ VP = 22 V (2) = 2 × 8 Ω SE @ VP = 30 V Fig 45. Gain as a function of frequency Fig 46. SVRR as a function of frequency AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 46 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 120 S/N (dB) 80 001aad778 0 αcs (dB) −20 001aad779 (2) (1) −40 −60 40 −80 (1) (2) 0 10−2 10−1 1 10 102 Po (W/channel) −100 10 102 103 104 fi (Hz) 105 Ri = 0 Ω (1) 2 × 4 Ω SE @ VP = 22 V (2) 2 × 8 Ω SE @ VP = 30 V PO = 1 W, CHVPREF = 47 μF (1) = 2 × 4 Ω SE @ VP = 22 V (2) = 2 × 8 Ω SE @ VP = 30 V Fig 47. S/N ratio as a function of output power Fig 48. Channel separation as a function of frequency 100 ηpo (%) 80 (2) (1) 001aad780 3.0 P (W) 2.0 001aad781 60 (2) 40 1.0 20 (1) 0 0 5 10 15 20 Po (W/channel) 0 10−2 10−1 1 10 102 Po (W/channel) fi = 1 kHz (1) 2 × 4 Ω SE @ VP = 22 V (2) 2 × 8 Ω SE @ VP = 30 V Remark: ηpo = (2 · Po) / (2 · Po + P) fi = 1 kHz (1) = 2 × 4 Ω SE @ VP = 22 V (2) = 2 × 8 Ω SE @ VP = 30 V Remark: Power dissipation in junction only. Fig 49. Efficiency as a function of output power Fig 50. Power dissipation as a function of output power AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 47 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 32 Po (W/channel) 24 (1) 001aaf886 (2) 16 (3) (4) 8 0 10 14 18 22 26 30 34 38 VP (V) fi = 1 kHz (1) 2 × 4 Ω SE @ THD+N = 10 % (2) 2 × 4 Ω SE @ THD+N = 0.5 % (3) 2 × 8 Ω SE @ THD+N = 10 % (4) 2 × 8 Ω SE @ THD+N = 0.5 % Fig 51. Maximum output power as a function of supply voltage 5.2 Audio characterization BTL 5.2.1 Performance figures BTL Table 10 shows the measured performance figures of the TDA8932BT two layer reference board (55 mm × 45 mm) configured in BTL configuration. VP = 22 V, RL = 8 Ω BTL, fosc = 320 kHz, fi = 1 kHz, Tamb = 25 °C unless specified otherwise. Table 10. Symbol VP Po(RMS) Performance figures Parameter supply voltage RMS output power Conditions/notes operates down to UVP threshold level; operates up to OVP threshold level RL = 8 Ω THD+N = 10 % THD+N = 0.5 % RL = 4 Ω; VP = 12 V THD+N = 10 % THD+N = 0.5 % THD+N total harmonic distortion-plus-noise Po = 1 W, AES17 brick wall filter 20 kHz RL = 8 Ω RL = 4 Ω, VP = 12 V ηpo output power efficiency Po = 15 W, VP = 22 V, RL = 8 Ω Po = 30 W, VP = 12 V, RL = 4 Ω AN10436_1 Min 10[1] - Typ 32.1 25.7 17.2 13.2 0.007 0.02 90 92 Max Unit 36[1] V W W W W % % % % © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 48 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier Table 10. Symbol Gv(cl) Vi(sens) Vn(o) S/N B SVRR Performance figures …continued Parameter input sensitivity voltage noise output voltage signal-to-noise ratio bandwidth supply voltage ripple rejection Conditions/notes Prated = 30 W, Ri = 4.7 kΩ MUTE mode unweighted, in relation to VO = 15.5 VRMS ±3 dB RL = 8 W, Vripple = 500 mVRMS, 100 Hz, inputs shorted RL = 4 W, Vripple = 500 mVRMS, 100 Hz, inputs shorted Min Typ 35.2 305 25 100 104 77 77 680 53 Max Unit dB mVrms μV μV dB Hz dB dB μA mA closed-loop voltage gain Vi = 100 mVRMS, 1 kHz, Ri = 4.7 kΩ, no load OPERATING mode, inputs shorted at INP, INN - 0 to 45,000 IP Iq [1] supply current quiescent current SLEEP mode, no load MUTE / OPERATING mode It is not recommended to operate the IC at the supply boundaries (10 V or 36 V) unless the supply is regulated well. 5.2.2 Performance graphs BTL 001aad783 001aad782 102 THD+N (%) 10 102 THD+N (%) 10 1 1 10−1 (1) 10−1 (1) (2) 10−2 (2) (3) 10−2 (3) 10−3 10−2 10−1 1 10 Po (W) 102 10−3 10−2 10−1 1 10 Po (W) 102 VP = 22 V, 8 Ω BTL (1) 6 kHz (2) 1 kHz (3) 100 Hz VP = 12 V, 4 Ω BTL (1) 6 kHz (2) 1 kHz (3) 100 Hz Fig 52. THD+N as a function of output power Fig 53. THD+N as a function of output power AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 49 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 102 THD+N (%) 10 001aae114 102 THD+N (%) 10 001aae115 1 1 10−1 (1) 10−1 10−2 (2) 10−2 (1) (2) 10−3 10 102 103 104 fi (Hz) 105 10−3 10 102 103 104 fi (Hz) 105 VP = 22 V, 8 Ω BTL (1) 10 W (2) 1 W VP = 12 V, 4 Ω BTL (1) 10 W (2) 1 W Fig 54. THD+N as a function of frequency Fig 55. THD+N as a function of frequency 40 Gv (dB) 30 001aae116 0 SVRR (dB) 001aae117 (2) (1) −20 −40 −60 20 (1) −80 (2) 10 10 102 103 104 fi (Hz) 105 −100 10 102 103 104 fi (Hz) 105 Vi = 100 mVRMS, Ri = 0 Ω (1) 4 Ω BTL @ VP = 12 V (2) 8 Ω BTL @ VP = 22 V Vripple = 500 mVRMS in relation to GND, shorted input, Ri = 0 Ω (1) 4 Ω BTL @ VP = 12 V (2) 8 Ω BTL @ VP = 22 V Fig 56. Gain as a function of frequency Fig 57. SVRR as a function of frequency AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 50 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 120 S/N (dB) 80 001aae118 70 Po (W) 60 50 (3) 001aaf893 (2) (1) 40 30 40 20 10 0 10−2 0 10 14 (1) (2) (4) 10−1 1 10 Po (W) 102 18 22 26 30 34 VP (V) Ri = 0 Ω (1) 4 Ω BTL @ VP = 12 V (2) 8 Ω BTL @ VP = 22 V fi = 1 kHz (1) 4 Ω BTL @ THD+N = 10 % (2) 4 Ω BTL @ THD+N = 0.5 % (3) 8 Ω BTL @ THD+N = 10 % (4) 8 Ω BTL @ THD+N = 0.5 % Fig 58. S/N ratio as a function of output power Fig 59. Maximum output power as a function of supply voltage 100 ηpo (%) 80 (1) 001aae119 3.0 P (W) 2.0 001aae120 (2) 60 40 1.0 20 (2) (1) 0 0 10 20 Po (W) 30 0 10−2 10−1 1 10 Po (W) 102 fi = 1 kHz (1) 4 Ω BTL @ VP = 12 V (2) 8 Ω BTL @ VP = 22 V Remark: ηpo = (Po) / (Po + P) fi = 1 kHz (1) 4 Ω BTL @ VP = 12 V (2) 8 Ω BTL @ VP = 22 V Remark: Power dissipation in junction only Fig 60. Efficiency as a function of output power Fig 61. Power dissipation as a function of output power AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 51 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 5.3 Thermal characterization The measured thermal resistance of the reference design with an SO32 package, a double-sided FR4 PCB (55 mm × 45 mm) and 35 μm copper, is equal to 44 K/W (free air and natural convection). When the junction temperature reaches the threshold level of the Thermal Foldback (140 °C to 150 °C), it starts to reduce gradually the output power so the maximum temperature will stay always within the Safe Operating Area. Figure 62 and Figure 63 show the TDA8932BT (S032) output power as a function of time at different supply voltages. The total output power of the device is 2 × Po, because the measurement is performed at SE configuration. 32 Po (W/channel) 24 (3) 001aaf887 32 Po (W/channel) 24 001aaf888 (2) (2) 16 (1) 16 (1) 8 8 0 0 120 240 360 480 t (s) 600 0 0 120 240 360 480 t (s) 600 RL = 2 × 4 Ω SE; fi = 1 kHz; 2 layer SO32 application board (55 mm × 45 mm) without heat sink. (1) VP = 22 V (2) VP = 26 V (3) VP = 29 V RL = 2 × 8 Ω SE; fi = 1 kHz; 2 layer SO32 application board (55 mm × 45 mm) without heat sink. (1) VP = 30 V (2) VP = 34 V Fig 62. SE output power as a function of time Fig 63. SE output power as a function of time Figure 64 and Figure 65 show the TDA8932BT output power as a function of time at different supply voltages. Total output power of the device is 1 × Po because the measurement is performed at BTL configuration. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 52 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 32 Po (W) (3) 001aaf896 60 Po (W) 50 (3) 001aaf899 24 (2) 40 (2) 16 (1) 30 (1) 20 8 10 0 0 120 240 360 480 t (s) 600 0 0 120 240 360 480 t (s) 600 RL = 4 Ω; fi = 1 kHz; 2 layer SO32 application board (55 mm × 45 mm) without heat sink. (1) VP = 12 V (2) VP = 13.5 V (3) VP = 15 V RL = 8 Ω; fi = 1 kHz; 2 layer SO32 application board (55 mm × 45 mm) without heat sink. (1) VP = 22 V (2) VP = 26 V (3) VP = 29 V Fig 64. BTL output power as a function of time Fig 65. BTL output power as a function of time 5.4 EMI characterization (FCC) The TDA8932B/33(B) reference design can comply easily with the FCC radiated emissions standards with 1 m of cable attached to all the I/Os. The spectrum analyzer is set at MAX hold and the output power is 2 × 1/8 Prated. REF 50.0 dBμW REF 80.0 dBμW ATTEN 10 dB 010aaa102 ATTEN 10 dB 010aaa101 DL DISPLAY LINE 50.0 50.0 dBμV dBμV BATTERY DL 50.0 DISPLAY LINE dBμV 50.0 dBμV BATTERY START 150 kHz RES BW 10 kHz VBW 10 kHz STOP 30.00 MHz SWP 750 msec START 30 MHz RES BW 100 kHz VBW 30 kHz STOP 300.0 MHz SWP 200 msec Fig 66. 150 kHz to 30 MHz Fig 67. 30 MHz to 300 MHz AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 53 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 6. Legal information 6.1 Definitions Suitability for use — NXP Semiconductors products are not designed, authorized or warranted to be suitable for use in medical, military, aircraft, space or life support equipment, nor in applications where failure or malfunction of an NXP Semiconductors product can reasonably be expected to result in personal injury, death or severe property or environmental damage. NXP Semiconductors accepts no liability for inclusion and/or use of NXP Semiconductors products in such equipment or applications and therefore such inclusion and/or use is at the customer’s own risk. Applications — Applications that are described herein for any of these products are for illustrative purposes only. NXP Semiconductors makes no representation or warranty that such applications will be suitable for the specified use without further testing or modification. Draft — The document is a draft version only. The content is still under internal review and subject to formal approval, which may result in modifications or additions. NXP Semiconductors does not give any representations or warranties as to the accuracy or completeness of information included herein and shall have no liability for the consequences of use of such information. 6.2 Disclaimers General — Information in this document is believed to be accurate and reliable. However, NXP Semiconductors does not give any representations or warranties, expressed or implied, as to the accuracy or completeness of such information and shall have no liability for the consequences of use of such information. Right to make changes — NXP Semiconductors reserves the right to make changes to information published in this document, including without limitation specifications and product descriptions, at any time and without notice. This document supersedes and replaces all information supplied prior to the publication hereof. 6.3 Trademarks Notice: All referenced brands, product names, service names and trademarks are the property of their respective owners. AN10436_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 12 December 2007 54 of 55 NXP Semiconductors AN10436 TDA8932B/33(B) Class-D audio amplifier 7. Contents 1 1.1 1.2 1.3 1.3.1 1.3.2 1.3.3 1.3.4 2 2.1 2.1.1 2.2 2.3 2.3.1 2.3.2 2.4 2.5 2.6 2.6.1 2.6.2 2.6.3 2.6.4 2.6.5 2.6.6 2.6.7 2.6.8 2.7 2.8 3 3.1 3.1.1 3.1.2 3.2 3.3 3.4 3.4.1 3.4.2 3.4.3 3.5 3.5.1 3.5.2 3.5.3 3.5.4 3.6 3.6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Fixed frequency pulse width modulated Class-D concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Typical application circuits (simplified) . . . . . . . 5 Asymmetrical supply stereo SE configuration . 5 Symmetrical supply stereo SE configuration . . 6 Asymmetrical supply mono BTL configuration . 7 Symmetrical supply mono BTL configuration . . 8 Functional IC description . . . . . . . . . . . . . . . . . 9 Control inputs . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Mode description . . . . . . . . . . . . . . . . . . . . . . 10 Half Supply Voltage (HVP) chargers. . . . . . . . 11 Pop free power supply on/off cycling . . . . . . . 11 Supply turn-on . . . . . . . . . . . . . . . . . . . . . . . . 11 Supply turn-off . . . . . . . . . . . . . . . . . . . . . . . . 11 Oscillator frequency . . . . . . . . . . . . . . . . . . . . 11 Device synchronization. . . . . . . . . . . . . . . . . . 12 Limiting and protection features . . . . . . . . . . . 13 Thermal Foldback (TF) . . . . . . . . . . . . . . . . . . 14 Cycle-by-cycle current limiting . . . . . . . . . . . . 14 Window Protection (WP). . . . . . . . . . . . . . . . . 14 UnderVoltage Protection (UVP) . . . . . . . . . . . 15 OverVoltage Protection (OVP) . . . . . . . . . . . . 15 UnBalance Protection (UBP) . . . . . . . . . . . . . 15 OverCurrent Protection (OCP) . . . . . . . . . . . . 16 OverTemperature Protection (OTP) . . . . . . . . 17 Pinning information . . . . . . . . . . . . . . . . . . . . . 17 Pin description . . . . . . . . . . . . . . . . . . . . . . . . 18 Design 2 x 5 W - 25 W audio amplifier (asymmetrical supply) . . . . . . . . . . . . . . . . . . . 19 Output power estimation. . . . . . . . . . . . . . . . . 19 TDA8932B output power estimation . . . . . . . . 20 TDA8933(B) output power estimation. . . . . . . 21 Peak output current estimation . . . . . . . . . . . . 23 Control circuit . . . . . . . . . . . . . . . . . . . . . . . . . 23 Analog audio input . . . . . . . . . . . . . . . . . . . . . 25 Input impedance . . . . . . . . . . . . . . . . . . . . . . . 26 Gain reduction . . . . . . . . . . . . . . . . . . . . . . . . 26 Reference decoupling (HVPREF). . . . . . . . . . 27 Speaker configuration and impedance . . . . . . 27 Filter inductor . . . . . . . . . . . . . . . . . . . . . . . . . 28 Filter capacitor . . . . . . . . . . . . . . . . . . . . . . . . 29 Zobel damping network . . . . . . . . . . . . . . . . . 29 Voltage clamp diodes . . . . . . . . . . . . . . . . . . . 31 Single ended capacitor . . . . . . . . . . . . . . . . . . 31 Voltage rating . . . . . . . . . . . . . . . . . . . . . . . . . 32 3.6.2 3.7 3.8 3.9 3.9.1 3.9.2 3.10 3.11 3.12 4 4.1 4.1.1 4.2 4.3 4.4 5 5.1 5.1.1 5.1.2 5.2 5.2.1 5.2.2 5.3 5.4 6 6.1 6.2 6.3 7 Lifetime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bootstrap capacitor . . . . . . . . . . . . . . . . . . . . Output RC snubber network . . . . . . . . . . . . . Layout recommendations. . . . . . . . . . . . . . . . EMC considerations. . . . . . . . . . . . . . . . . . . . Thermal considerations . . . . . . . . . . . . . . . . . Schematic - revision 3.00. . . . . . . . . . . . . . . . Bill of materials - revision 3.00 . . . . . . . . . . . . PCB layout - Revision 2 . . . . . . . . . . . . . . . . . Power supply. . . . . . . . . . . . . . . . . . . . . . . . . . Supply filtering . . . . . . . . . . . . . . . . . . . . . . . . Lifetime electrolytic capacitor . . . . . . . . . . . . . Supply GND connection. . . . . . . . . . . . . . . . . Low frequency supply pumping effect . . . . . . Unregulated or weak power supply . . . . . . . . Performance characterization TDA8932B. . . Audio characterization SE . . . . . . . . . . . . . . . Performance figures SE. . . . . . . . . . . . . . . . . Performance graphs SE. . . . . . . . . . . . . . . . . Audio characterization BTL . . . . . . . . . . . . . . Performance figures BTL . . . . . . . . . . . . . . . . Performance graphs BTL. . . . . . . . . . . . . . . . Thermal characterization . . . . . . . . . . . . . . . . EMI characterization (FCC) . . . . . . . . . . . . . . Legal information . . . . . . . . . . . . . . . . . . . . . . Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . . Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 32 33 33 33 36 38 39 39 41 41 41 41 42 43 44 44 44 45 48 48 49 52 53 54 54 54 54 55 Please be aware that important notices concerning this document and the product(s) described herein, have been included in section ‘Legal information’. © NXP B.V. 2007. All rights reserved. For more information, please visit: http://www.nxp.com For sales office addresses, please send an email to: salesaddresses@nxp.com Date of release: 12 December 2007 Document identifier: AN10436_1