NXP Semiconductors TDA8932B Product Data Sheet

NXP Semiconductors TDA8932B Product Data Sheet Manual pdf 7 page image

TDA8932B_3 © NXP B.V. 21 June 2007. All rights reserved.Product data sheet Rev. 03— 21 June 2007 7 of 48NXP Semiconductors TDA8932BClass-D audio amplifier8.3 Pulse width modulation frequencyThe output signal of the amplifier is a PWM signal with a carrier frequency ofapproximately 320 kHz. Using a 2nd-order low-pass filter in the application results in ananalog audio signal across the loudspeaker. The PWM switching frequency can be set byan external resistor Rosc connected between pins OSCREF and VSSD(HW). The carrierfrequency can be set between 300 kHz and 500 kHz. Using an external resistor of 39 kΩ,the carrier frequency is set to an optimized value of 320 kHz (see Figure 5).If two or more TDA8932B devices are used in the same audio application, it isrecommended to synchronize the switching frequency of all devices. This can be realizedby connecting all pins OSCIO together and configure one of the TDA8932B in theapplication as clock master, while the other TDA8932B devices are configured in slavemode.Pin OSCIO is a 3-state input or output buffer. Pin OSCIO is configured in master mode asoscillator output and in slave mode as oscillator input. Master mode is enabled by applyinga resistor while slave mode is entered by connecting pin OSCREF directly to pin VSSD(HW)(without any resistor).The value of the resistor also sets the frequency of the carrier which can be estimated bythe following formula:Fig 4. Start-up sequenceVPPOWERUPDREFHVPREFHVP1, HVP2ENGAGE2.0 V (typical)1.2 V (typical)audioPWMOUT1, OUT2DIAGOSCIO001aaf885operating operatingPWMPWMsleepmute operating faultAUDIO AUDIO AUDIO≤ 0.8 V