NXP Semiconductors TDA8932B - Manual (Page 7)

TDA8932B_4 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 04 — 18 December 2008 7 of 48
NXP Semiconductors
TDA8932B
Class-D audio amplifier
8.3 Pulse width modulation frequency
The output of the amplifier is a PWM signal with a carrier frequency of approximately
320 kHz. Using a 2nd-order low-pass filter in the application results in an analog audio
signal across the loudspeaker. The PWM switching frequency can be set by an external
resistor Rosc connected between pins OSCREF and V
SSD(HW)
. The carrier frequency can
be set between 300 kHz and 500 kHz. Using an external resistor of 39 k
Ω
, 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 is
recommended to synchronize the switching frequency of all devices. This can be realized
by connecting all OSCIO pins together and configure one of the TDA8932B in the
application as clock master, while the other TDA8932B devices are configured in slave
mode.
Pin OSCIO is a 3-state input or output buffer. Pin OSCIO is configured in master mode as
an oscillator output and in slave mode as an oscillator input. Master mode is enabled by
applying a resistor while slave mode is entered by connecting pin OSCREF directly to pin
V
SSD(HW)
(without any resistor).
The value of the resistor also sets the frequency of the carrier which can be estimated by
the following formula:
Fig 4. Start-up sequence
V P
POWERUP
DREF
HVPREF
HVP1, HVP2
ENGAGE
2.0 V (typical)
1.2 V (typical)
audio
PWM
OUT1, OUT2
DIAG
OSCIO
001aaf885
operating operating
PWM PWM
sleep mute operating fault
AUDIO AUDIO AUDIO
≤
0.8 V