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TDA8922C データシート(PDF) 10 Page - NXP Semiconductors |
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TDA8922C データシート(HTML) 10 Page - NXP Semiconductors |
10 / 40 page TDA8922C_1 © NXP B.V. 2009. All rights reserved. Product data sheet Rev. 01 — 7 September 2009 10 of 40 NXP Semiconductors TDA8922C 2 × 75 W class-D power amplifier • Short-circuit impedance < Zth: the amplifier limits the maximum output current to IORM and at the same time discharges the capacitor on pin PROT. When CPROT is fully discharged, the amplifier shuts down completely and an internal timer is started. The value of the protection capacitor (CPROT) connected to pin PROT can be between 10 pF and 220 pF (typically 47 pF). While OCP is activated, an internal current source is enabled that will discharge CPROT. When OCP is activated, the active power transistor is turned off and the other power transistor is turned on to reduce the current (CPROT is partially discharged). Normal operation is resumed at the next switching cycle (CPROT is recharged). CPROT is partially discharge each time OCP is activated during a switching cycle. If the fault condition that caused OCP to be activated persists long enough to fully discharge CPROT, the amplifier will switch off completely and a restart sequence will be 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 short. 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 TDA8922C amplifier is fully protected against short-circuit conditions while avoiding audio holes. [1] Tested using three samples and an external clock. 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 TDA8922C is switching from Standby to Mute. Table 4. Current limiting behavior during low output impedance conditions at different values of CPROT[1] Type VDD/VSS (V) VI (mV, p-p) f (Hz) CPROT (pF) PWM output stops Short (Zth =0 Ω) Short (Zth = 0.5 Ω) Short (Zth =1 Ω) TDA8922C +29.5/ −29.5 500 20 10 yes yes yes 1000 10 yes yes yes 20 15 yes yes yes 1000 15 yes no no 1000 220 no no no |
同様の部品番号 - TDA8922C |
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同様の説明 - TDA8922C |
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