tda7498l STMicroelectronics, tda7498l Datasheet - Page 21

• Manufacturer Part Number: tda7498l
• Description: 80 W + 80 W Dual Btl Class-d Audio Amplifier
• Manufacturer: STMicroelectronics

TDA7498L
5.5
5.5.1
5.5.2
Internal and external clocks
The clock of the class-D amplifier can be generated internally or can be driven by an
external source.
If two or more class-D amplifiers are used in the same system, it is recommended that all
devices operate at the same clock frequency. This can be implemented by using one
TDA7498L as master clock, while the other devices are in slave mode, that is, externally
clocked. The clock interconnect is via pin SYNCLK of each device. As explained below,
SYNCLK is an output in master mode and an input in slave mode.
Master mode (internal clock)
Using the internal oscillator, the output switching frequency, f
resistor, R
where R
In master mode, pin SYNCLK is used as a clock output pin whose frequency is:
For master mode to operate correctly then resistor R
below in
Slave mode (external clock)
In order to accept an external clock input the pin ROSC must be left open, that is, floating.
This forces pin SYNCLK to be internally configured as an input as given in
The output switching frequency of the slave devices is:
Table 9.
Figure 24. Master and slave connection
Master
Slave
f
f
f
SW
SYNCLK
SW
OSC
= 10
Table
= f
OSC
SYNCLK
Mode
How to set up SYNCLK
Cosc
100 nF
is in kΩ.
= 2 * f
6
, connected to pin ROSC:
9.
/ ((R
SW
OSC
/ 2
ROSC
TDA7498L
* 16 + 182) * 4) kHz
Master
Rosc
39 kΩ
Doc ID 16504 Rev 1
R
Floating (not connected)
SYNCLK
OSC
Output
< 60 kΩ
ROSC
OSC
SYNCLK
must be less than 60 kΩ as given
Input
TDA7498L
SW
Slave
Output
Input
, is controlled by the
Applications information
ROSC
SYNCLK
Table
9.
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