STEVAL-CCA040V1

AN4176 Application note 4 x 10 W class-AB amplifier demonstration board based on the STA540SAN Introduction This application note describes the STEVAL-CCA040V1 demonstration board designed for the evaluation of the STA540SAN which contains four single-ended class-AB amplifiers assembled in the Clipwatt15 package. The device is able to deliver 4 x 10 W in single-ended (SE) configuration with VCC at 17 V and a 4 Ω load or 2 x 26 W in bridge-tied load (BTL) configuration with VCC at 14.4 V and a 4 Ω load. This application note provides details on the demonstration board connections, performance (operating characteristics), and suggestions for layout design in order to avoid critical issues. The board schematics are also included in this document. Figure 1. February 2013 STEVAL-CCA040V1 Doc ID 023741 Rev 1 1/22 www.st.com Contents AN4176 Contents 1 Reference documents and terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Test conditions, connections and electrical characteristics of the demonstration board 3 4 5 6 2/22 4 2.1 Power supply and interface connections . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2 Output configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.3 Equipment requirement and connections . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.4 Output configuration settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Board schematics and PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.1 Board schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.2 PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.3 Design guidelines for schematic and PCB layout . . . . . . . . . . . . . . . . . . . 10 3.3.1 Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.3.2 Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Operating characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.1 Single-ended output configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.2 BTL output configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Thermal information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 5.1 Calculating power dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 5.2 Selecting the heatsink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Doc ID 023741 Rev 1 AN4176 1 Reference documents and terminology Reference documents and terminology Reference documents for operation of the demonstration board include: ● STA540SAN datasheet ● Schematic diagram ● PCB layout ● Operating characteristics The terminology and acronyms used in this document are defined as follows: ● THD+N vs. Pout: Total Harmonic Distortion (THD) plus noise versus output power ● THD+N vs. Freq: Total Harmonic Distortion plus noise versus frequency ● S/N ratio: Signal-to-Noise ratio ● FFT: Fast Fourier Transform algorithm (method) ● Xtalk: Channel separation OUT1 to OUT2 or OUT2 to OUT1 and OUT3 to Out4 or OUT4 to OUT3 channel crosstalk Doc ID 023741 Rev 1 3/22 Test conditions, connections and electrical characteristics of the demonstration board 2 Test conditions, connections and electrical characteristics of the demonstration board 2.1 Power supply and interface connections AN4176 Connect the power supply to the VCC connector (CN7), supply voltage ranging from 8 V to 22 V. Connect the analog input cable to the RCA connectors (CN1) on the demonstration board. The other side must be connected to a signal source such as Audio Precision analog outputs or a DVD player. 2.2 Output configuration The STEVAL-CCA040V1 demonstration board can be configured to have a 4-channel single-ended output, a 2-channel BTL output or a 2-channel single-ended output plus 1channel BTL output. 2.3 Equipment requirement and connections The equipment needed to operate the board includes: Figure 2. ● Audio generator and analyzer Audio Precision AP 2722 ● Oscilloscope Tektronix 3034B ● DC power supply ● Dummy load Test wiring diagram Audio Precision Equipment Analog generator Monitor output Analog analyzer Analog output Dummy load Tektronix Digital Oscilloscope TDS3034B STA540SAN demo board DC Power Supply VCC 8V~22Vdc 4/22 Doc ID 023741 Rev 1 AN4176 Test conditions, connections and electrical characteristics of the demonstration board Figure 3. STEVAL-CCA040V1 overview OUT4 OUT2 OUT3 OUT1 DC supply input Standby control Analog signal input 2.4 Output configuration settings Figure 4. 4-channel single-ended configuration OUT4 OUT2 OUT3 OUT1 Note: Jumpers in blue are open. Doc ID 023741 Rev 1 5/22 Test conditions, connections and electrical characteristics of the demonstration board Figure 5. 2-channel single-ended and 1-channel BTL configuration OUT2 OUT3 OUT1 Note: Jumpers in blue are open, jumpers in yellow are closed. Figure 6. 2-channel BTL configuration OUT2 OUT1 Note: 6/22 Jumpers in yellow are closed. Doc ID 023741 Rev 1 AN4176 AN4176 2.5 Test conditions, connections and electrical characteristics of the demonstration board Electrical characteristics The following table shows the output for the 4 single-ended and BTL configurations given the following conditions: Vcc = +17 V, Gain 20 dB; Tamb=25.5 °C; Input Freq = 1 kHz; Ref Level=1 W (0 dBr), Load = 4 Ω (resistive dummy load). Table 1. Electrical characteristics Parameter THD+N vs. power Output power 10% THD Condition Result Pout = 1 W 0.0555% Single-ended 10 W BTL (Vcc at 14.4 V) 26 W Iocp 3.5 A No filter -70.5 dB AW - filter -92.3 dB 1kHz -65.8 dB SNR Xtalk Doc ID 023741 Rev 1 7/22 Board schematics and PCB layout 3.1 Board schematic Figure 7. AN4176 3 STEVAL-CCA040V1 schematic Doc ID 023741 Rev 1 Board schematics and PCB layout 8/22 AN4176 3.2 Board schematics and PCB layout PCB layout Figure 8. PCB layout - top view Figure 9. PCB layout - bottom view Doc ID 023741 Rev 1 9/22 Board schematics and PCB layout AN4176 3.3 Design guidelines for schematic and PCB layout 3.3.1 Schematic Criteria for selection of components ● Absolute maximum rate (input VCC supply voltage ): 24 V ● Output DC-decoupling capacitor 2200 µF for each single-ended power output is recommended Decoupling capacitors There are two different ways to utilize these capacitors: ● The decoupling capacitor(s) can be shared among channels; the layout must be designed to implement a "star route" for the VCC paths. ● One decoupling capacitor can be used for each channel. A 100 nF decoupling capacitor (mandatory) must be placed as close as possible to the IC pins. This solution is implemented in the STA540SAN demonstration board. Driving the standby pin The STA540SAN standby pin cannot be directly driven by a voltage source having current capability higher than 5 mA, so a 10k ohm plus 10 µF RC network has been inserted between the external control signal and standby pin of the STA540SAN. 3.3.2 Layout The following layout recommendations should be implemented: ● To avoid the effect due to the parasitic inductive coil generated by the copper wires, an SMD type ceramic capacitor (100 nF) is recommended in order to balance the reactance. The ceramic capacitor (mandatory) must be placed as close as possible to the related pins. Figure 10. Decoupling capacitors Ground pin and Vcc pin of 100nF capacitors should be directly connected to related IC pin 10/22 Doc ID 023741 Rev 1 AN4176 Board schematics and PCB layout ● Signal ground and power ground routing should be connected to the bulk capacitor negative terminal. The signal ground is separated from the power ground routing. ● Standby capacitor ground, SVR capacitor ground and input signal ground should be connected to S_GND. ● SVR capacitor should be placed as close as possible to the STA540SAN Figure 11. Signal ground and power ground routing (top) SVR Cap P-GND Grounding node of S_GND and PGND S-GND Figure 12. Signal ground and power ground routing (bottom) S-GND P-GND Doc ID 023741 Rev 1 11/22 Operating characteristics AN4176 4 Operating characteristics 4.1 Single-ended output configuration Figure 13. SE output power vs. supply voltage SE, Rload =4ohm f=1kHz THD =10% THD =1% Figure 14. SE THD vs. output power, VCC = 17 V 20 10 5 2 1 % 0.5 15 kHz 0.2 0.1 0.05 100Hz 1 KHz 0.02 0.01 20m 50m 100m 200m 500m W 12/22 Doc ID 023741 Rev 1 1 2 5 10 AN4176 Operating characteristics Figure 15. SE THD vs. frequency Figure 16. SE frequency response at 1 W output +4 +3 +2 +1 -0 -1 d B r -2 A -4 -3 -5 -6 -7 -8 -9 -10 20 50 100 200 500 1k 2k 5k 10k 20k Hz Doc ID 023741 Rev 1 13/22 Operating characteristics AN4176 Figure 17. SE signal-to-noise ratio at 1 W output +0 -10 -20 -30 -40 d B r -50 -60 w/o Aw A -70 -80 Aw -90 -100 -110 20 50 100 200 500 1k 2k 5k 10k 20k 1k 2k 5k 10k 20k Hz Figure 18. SE FFT 1 kHz, 0 dB at 1 W output +0 -10 -20 -30 -40 -50 -60 -70 d B r A -80 -90 -100 -110 -120 -130 -140 -150 -160 -170 -180 20 50 100 200 500 Hz 14/22 Doc ID 023741 Rev 1 AN4176 Operating characteristics Figure 19. SE FFT 1 kHz, -60 dB at 1 W output +0 -10 -20 -30 -40 -50 -60 -70 d B r A -80 -90 -100 -110 -120 -130 -140 -150 -160 -170 -180 20 50 100 200 500 1k 2k 5k 10k 20k 10k 20k Hz Figure 20. SE Xtalk CH1 vs. CH2 +0 -10 -20 -30 -40 d B -50 CH1 to CH2 -60 -70 CH2 to CH1 -80 -90 -100 20 50 100 200 500 1k 2k 5k Hz Doc ID 023741 Rev 1 15/22 Operating characteristics 4.2 AN4176 BTL output configuration Figure 21. BTL output power vs. supply voltage 40 BTL Rload =4ohm f=1kHz Output Power (W) 35 30 THD =10% 25 20 THD =1% 15 10 5 0 8 9 10 11 12 13 14 15 16 17 18 Supply Voltage (V) Figure 22. BTL THD vs. output power 10 5 2 1 0.5 15 kHz % 0.2 100Hz 0.1 0.05 1 KHz 0.02 0.01 1m 2m 5m 10m 20m 50m 100m 200m W 16/22 Doc ID 023741 Rev 1 500m 1 2 5 10 20 30 AN4176 Operating characteristics Figure 23. BTL THD vs. frequency 1 0.5 0.2 % 0.1 0.05 0.02 0.01 20 50 100 200 500 1k 2k 5k 10k 20k 2k 5k 10k 20k Hz Figure 24. BTL frequency response at 1 W output +4 +3.5 +3 +2.5 +2 +1.5 +1 +0.5 d B r A -0 -0.5 -1 -1.5 -2 -2.5 -3 -3.5 -4 -4.5 -5 20 50 100 200 500 1k Hz Doc ID 023741 Rev 1 17/22 Operating characteristics AN4176 Figure 25. BTL signal-to-noise ratio at 1 W output +0 -10 -20 -30 -40 d B r A -50 W/O AW -60 -70 -80 AW -90 -100 20 50 100 200 500 1k 2k 5k 10k 20k 1k 2k 5k 10k 20k Hz Figure 26. FFT 1 kHz, 0 dB at 1 W output +0 -10 -20 -30 -40 -50 -60 -70 d B r A -80 -90 -100 -110 -120 -130 -140 -150 -160 -170 -180 20 50 100 200 500 Hz 18/22 Doc ID 023741 Rev 1 AN4176 Operating characteristics Figure 27. FFT 1 kHz, -60 dB at 1 W output +0 -10 -20 -30 -40 -50 -60 -70 d B r A -80 -90 -100 -110 -120 -130 -140 -150 -160 -170 -180 20 50 100 200 500 1k 2k 5k 10k 20k 10k 20k Hz Figure 28. BTL Xtalk +0 -10 -20 -30 -40 d B -50 CH3/4 to CH1/2 -60 -70 -80 CH1/2 to CH3/4 -90 -100 20 50 100 200 500 1k 2k 5k Hz Doc ID 023741 Rev 1 19/22 Thermal information AN4176 5 Thermal information 5.1 Calculating power dissipation For SE configuration, the equation for power dissipation is: 2 Vcc Pdmax = ---------------2 2π RL For BTL configuration, the equation for power dissipation is: 2 Pdmax = 2Vcc --------------2 π RL For example, for a 2.1-channel output configuration, when VCC is 14.4 V, 2 single-ended channel loads are 4 ohm, and 1 BTL channel load is 8 ohm, the maximum power dissipation in the STA540SAN is: ⎛ Vcc 2 ⎞ 2Vcc 2 Pdmax = 2 × ⎜ ---------------⎟ + --------------⎝ 2π 2 RL⎠ π 2 RL 2 2 ⎛ ⎞ ⎛ 14.4 -⎞ 14.4 -⎟ + ⎜ 2 × --------------------Pdmax = 2 × ⎜ -----------------------------⎟ 2 ⎝ 2 × 3.14 2 × 4⎠ ⎝ 3.14 × 8⎠ Pdmax = 5.26 + 5.26 = 10.52W 5.2 Selecting the heatsink According to the STA540SAN datasheet, the thermal impedance between junction and case is 4.5 °C/W, the thermal muting threshold is 150 °C, when ambient temperature is 50 °C. To avoid thermal protection intervention, the heatsink thermal impedance should be: 150 – 50 Rth heat sin k = ⎛⎝ ---------------------⎞⎠ – Rth – j case Pd Based on the above condition, the minimum heatsink thermal impedance is: 100 Rth heat sin k = ⎛ -------------⎞ – 4.5 = 5°C ⁄ W ⎝ 10.52⎠ When the average music listening power concept is considered, dissipation power is 60% of max dissipation power, thus the heatsink can be smaller. Therefore, the heatsink thermal impedance is: 100 Rth heat sin k = ⎛ ---------------------------⎞ – 4.5 = 11.34°C ⁄ W ⎝ 10.52 × 0.6⎠ 20/22 Doc ID 023741 Rev 1 AN4176 6 Revision history Revision history Table 2. Document revision history Date Revision 12-Feb-2013 1 Changes Initial release. Doc ID 023741 Rev 1 21/22 AN4176 Please Read Carefully: Information in this document is provided solely in connection with ST products. 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