TDA8920C Datasheet, PDF (8/40 Pages) NXP Semiconductors – 2 X110 W class-D power amplifier

NXP Semiconductors
TDA8920C
2 × 110 W class-D power amplifier
8.2 Pulse-width modulation frequency
The output signal of the amplifier is a PWM signal with a carrier frequency typically
between 300 kHz and 400 kHz. Using a 2nd-order LC demodulation filter in the
application results in an analog audio signal across the loudspeaker. The carrier
frequency is determined by an external resistor R_OSC, connected between pin OSC and
pin VSSA. An optimal setting for the carrier frequency is between 300 kHz and 400 kHz.
The carrier frequency is set to 345 kHz by connecting a 30 kΩ external resistor between
pin OSC and VSSA. See Table 8 for more details.
If two or more class-D amplifiers are used in the same audio application, it is
recommended that all devices use an external clock circuit to ensure that they operate at
the same switching frequency.
8.3 Protection
The following protection strategies are provided:
• Thermal protection:
– Thermal FoldBack (TFB)
– OverTemperature Protection (OTP)
• OverCurrent Protection (OCP, diagnostic output on pin PROT)
• Window Protection (WP)
• Supply voltage protection:
– UnderVoltage Protection (UVP)
– OverVoltage Protection (OVP)
– UnBalance Protection (UBP)
The device reacts to fault conditions differently for each protection type.
8.3.1 Thermal protection
The TDA8920C has an advanced thermal protection strategy. It consists of a TFB function
that gradually reduces the output power within a defined temperature range. If the
temperature continues to rise, OTP is implemented, shutting down the device completely.
8.3.1.1 Thermal FoldBack (TFB)
If the junction temperature (T_j) exceeds the defined threshold value, the gain is gradually
reduced. This reduces the output signal amplitude and the power dissipation, eventually
stabilizing the temperature.
TDA8920C_1
Preliminary data sheet
Rev. 01 — 29 September 2008
© NXP B.V. 2008. All rights reserved.
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