Datasheet TDA8920CTH (NXP) - 10

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NXP Semiconductors TDA8920C 2
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110 W class-D power amplifier
When OCP is activated, the power transistors are turned off. They are turned on again during the next switching cycle. If the output current is still greater than the OCP threshold, they will be immediately switched off again. This switching will continue until CPROT is fully discharged. The amplifier will then be switched off completely and a restart sequence initiated. After a fixed period of 100 ms, the amplifier will attempt to switch on again, but will fail if the output current still exceeds the OCP threshold. The amplifier will continue trying to switch on every 100 ms. The average power dissipation will be low in this situation because the duty cycle is low. Switching the amplifier on and off in this way will generate unwanted ‘audio holes’. This can be avoided by increasing the value of CPROT (up to 220 pF) to delay amplifier switch-off. CPROT will also prevent the amplifier switching off due to transient frequency-dependent impedance drops at the speakers. The amplifier will switch on, and remain in Operating mode, once the overcurrent condition has been removed. OCP ensures the TDA8920C amplifier is fully protected against short-circuit conditions while avoiding audio holes.
Table 4. Current limiting behavior during low output impedance conditions at different values of CPROT Type VP VI (mV, p-p) f (Hz) CPROT PWM output stops (V) (pF) Short Short Short (Zth = 0
Ω
) (Zth = 0.5
Ω
) (Zth = 1
Ω
)
TDA8920C 29.5 500 20 10 yes yes OVP[1] 1000 10 yes yes no 20 15 yes yes OVP[1] 1000 15 yes no no 1000 220 no no no [1] OVP can be triggered by supply pumping; see Section 13.6.
8.3.3 Window Protection (WP)
Window Protection (WP) checks the conditions at the output terminals of the power stage and is activated:
•
During the start-up sequence, when the TDA8920C is switching from Standby to Mute. Start-up will be interrupted If a short-circuit is detected between one of the output terminals and pin VDDP1/VDDP2 or VSSP1/VSSP2. The TDA8920C will wait until the short-circuit to the supply lines has been removed before resuming start-up. The short circuit will not generate large currents because the short-circuit check is carried out before the power stages are enabled.
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When the amplifier is shut down completely because the OCP circuit has detected a short circuit to one of the supply lines. WP will be activated when the amplifier attempts to restart after 100 ms (see Section 8.3.2). The amplifier will not start-up again until the short circuit to the supply lines has been removed. TDA8920C_2 © NXP B.V. 2009. All rights reserved.
Product data sheet Rev. 02 — 11 June 2009 10 of 39
Document Outline 1. General description 2. Features 3. Applications 4. Quick reference data 5. Ordering information 6. Block diagram 7. Pinning information 7.1 Pinning 7.2 Pin description 8. Functional description 8.1 General 8.2 Pulse-width modulation frequency 8.3 Protection 8.3.1 Thermal protection 8.3.1.1 Thermal FoldBack (TFB) 8.3.1.2 OverTemperature Protection (OTP) 8.3.2 OverCurrent Protection (OCP) 8.3.3 Window Protection (WP) 8.3.4 Supply voltage protection 8.4 Differential audio inputs 9. Limiting values 10. Thermal characteristics 11. Static characteristics 12. Dynamic characteristics 12.1 Switching characteristics 12.2 Stereo SE configuration characteristics 12.3 Mono BTL application characteristics 13. Application information 13.1 Mono BTL application 13.2 Pin MODE 13.3 Estimating the output power 13.3.1 Single-Ended (SE) 13.3.2 Bridge-Tied Load (BTL) 13.4 External clock 13.5 Heatsink requirements 13.6 Pumping effects 13.7 Application schematic 13.8 Curves measured in reference design 14. Package outline 15. Soldering of SMD packages 15.1 Introduction to soldering 15.2 Wave and reflow soldering 15.3 Wave soldering 15.4 Reflow soldering 16. Soldering of through-hole mount packages 16.1 Introduction to soldering through-hole mount packages 16.2 Soldering by dipping or by solder wave 16.3 Manual soldering 16.4 Package related soldering information 17. Revision history 18. Legal information 18.1 Data sheet status 18.2 Definitions 18.3 Disclaimers 18.4 Trademarks 19. Contact information 20. Contents