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TDA8933 数据表(PDF) 10 Page - NXP Semiconductors |
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TDA8933 数据表(HTML) 10 Page - NXP Semiconductors |
10 / 47 page TDA8933_1 © NXP B.V. 2007. All rights reserved. Preliminary data sheet Rev. 01 — 15 May 2007 10 of 47 NXP Semiconductors TDA8933 Class-D audio amplifier 8.4.1 Thermal Foldback (TF) If the junction temperature of the TDA8933 exceeds the threshold level (Tj > 140 °C), the gain of the amplifier is decreased gradually to a level where the combination of dissipation (P) and the thermal resistance from junction to ambient (Rth(j-a)) results in a junction temperature around the threshold level. This means that the device will not switch off completely, but remains operational at lower output power levels. With music output signals, this feature enables high peak output powers while still operating without any external heat sink other than the printed-circuit board area. If the junction temperature still increases due to external causes, the OverTemperature Protection (OTP) shuts down the amplifier completely. 8.4.2 OverTemperature Protection (OTP) If the junction temperature Tj > 155 °C, the power stage will shut down immediately. 8.4.3 OverCurrent Protection (OCP) When the output current of the device exceeds 2 A due to a short-circuit across the load or an impedance drop, 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. If the current exceeds 2 A due to a low ohmic short from the demodulated output (after the inductor) to either VSS or VDD both power stages become floating. The DIAG is set low for 50 ms and the internal timer of 100 ms is started. The timer will keep both power stages disabled for 100 ms. As long as the short remains, this cycle will repeat. The average power dissipation in the TDA8933 will be low because the short-circuit current will flow only during a very small part of the timer cycle of 100 ms. 8.4.4 Window Protection (WP) WP checks the PWM output voltage before switching from Sleep mode to Mute mode (outputs switching) and is activated: • During the start-up sequence, when pin POWERUP is switched from Sleep mode to Mute mode. In the event of a short-circuit at one of the output terminals to VDDP1,VSSP1,VDDP2 or VSSP2 the start-up procedure is interrupted and the TDA8933 waits for open-circuit outputs. Because the check is done before enabling the power stages, no large currents will flow in the event of a short-circuit. • When the amplifier is shut down completely, due to activation of the OCP because a short to one of the supply lines is made, then during restart (after 100 ms) the window protection will be activated. As a result, the amplifier will not start up until the short to the supply lines is removed. 8.4.5 Supply voltage protections If the supply voltage drops below 10 V, the UVP circuit is activated and the system will shut down directly. This switch-off will be silent and without pop noise. When the supply voltage rises above the threshold level, the system is restarted again after 100 ms. |
类似零件编号 - TDA8933 |
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类似说明 - TDA8933 |
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