TDA8922CJ View Datasheet(PDF) - NXP Semiconductors.

Part Name

Description

Manufacturer

TDA8922CJ

2×75 W class-D power amplifier

NXP Semiconductors. 

NXP Semiconductors

TDA8922C

2 × 75 W class-D power amplifier

8.2 Pulse-width modulation frequency

The amplifier output signal is a PWM signal with a typical carrier frequency of between

250 kHz and 450 kHz. A second order LC demodulation filter on the output converts the

PWM signal into an analog audio signal. The carrier frequency is determined by an

external resistor, ROSC, connected between pins OSC and VSSA. The optimal carrier

frequency setting is between 250 kHz and 450 kHz.

The carrier frequency is set to 345 kHz by connecting an external 30 kΩ resistor between

pins OSC and VSSA. See Table 9 for more details.

If two or more Class D amplifiers are used in the same audio application, it is

recommended that an external clock circuit be used with all devices (see Section 13.4).

This will ensure that they operate at the same switching frequency, thus avoiding beat

tones (if the switching frequencies are different, audible interference known as ‘beat tones’

can be generated).

8.3 Protection

The following protection circuits are incorporated into the TDA8922C:

• Thermal protection:

– Thermal FoldBack (TFB)

– OverTemperature Protection (OTP)

• OverCurrent Protection (OCP)

• Window Protection (WP)

• Supply voltage protection:

– UnderVoltage Protection (UVP)

– OverVoltage Protection (OVP)

– UnBalance Protection (UBP)

How the device reacts to a fault conditions depends on which protection circuit has been

activated.

8.3.1 Thermal protection

The TDA8922C employes an advanced thermal protection strategy. A TFB function

gradually reduces the output power within a defined temperature range. If the temperature

continues to rise, OTP is activated to shut down the device completely.

8.3.1.1 Thermal FoldBack (TFB)

If the junction temperature (Tj) exceeds the thermal foldback activation threshold, the gain

is gradually reduced. This reduces the output signal amplitude and the power dissipation,

eventually stabilizing the temperature.

TDA8922C_1

Product data sheet

Rev. 01 — 7 September 2009

© NXP B.V. 2009. All rights reserved.

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