TDA749313TR Datasheet, PDF (15/30 Pages) STMicroelectronics – 3-watt 3-watt dual BTL class-D audio amplifier

TDA7493
Applications information
5.5
Note:
Internal clock and external clock
The clock of the class-D amplifier can be generated internally or it can be synchronous with
the external clock. If two or more class-D amplifiers are used in the same system, it is better
to have all devices working at the same frequency. This is realized by using one TDA7493
as clock master and the others as slaves. All SYNCLK pins are connected together as
shown in Figure 8.
In master mode or with a single TDA7493, the output switching frequency is controlled by
the resistor connected to pin ROSC. The switching frequency is:
f_SW = 10⁶ / (R_OSC * 64 + 840)
where R_OSC is in kΩ and f_SW is in kHz.
In this configuration pin SYNCLK is an output whose frequency is also determined by R_OSC:
f_SYNCLK = 10⁶ / (R_OSC * 32 + 420) = 2 * f_SW
R_OSC should be lower than 60 kΩ in master mode to avoid operating in error mode.
In slave mode, pin ROSC can be floating to force pin SYNCLK as input in order to accept the
master clock. The switching frequency in this mode is:
f_SW = f_SYNCLK / 2
Table 9.
Master and slave mode
Mode
Pin ROSC
Pin SYNCLK
Master
Slave
R_OSC < 60 kΩ
Floating
Output
Input
Figure 8. Master and slave modes
Master
TDA7493
ROSC SYNCLK
Output
Slave
TDA7493
SYNCLK
ROSC
Input
C_OSC
100 nF
R_OSC
39 kΩ
Doc ID 14570 Rev 6
15/30