NXP Semiconductors TFA9812 - Manual (Page 14)

TFA9812_2 © NXP B.V. 2009. All rights reserved.
Preliminary data sheet Rev. 02 — 22 January 2009 14 of 66
NXP Semiconductors
TFA9812
BTL stereo Class-D audio amplifier with I 2 S input
In I 2 C control mode communication is enabled after 4 ms. The preferred I 2 C settings can
be made within 66 ms before the PLL starts running. Finally, the output stages are
enabled and the audio level is increased via a demute sequence if mute has previously
been disabled.
Remark: In I 2 C mode soft mute is enabled by default. It can be disabled at any time while
I 2 C communication is valid. In order to prevent audio clicks volume control (default setting
is 0 dB) should be set before soft mute is disabled.
Remark: For a proper start-up in I 2 S master mode and I 2 C mode the following sequence
should be followed:
1. The I 2 S master setting should be set and keep the default sample rate setting active.
2. Next, another sample rate setting than the default one should be selected.
3. Finally, when the default sample rate is used the default sample rate setting should be
selected again.
8.3.2 Power-down
Figure 3 includes the power-down timing while Table 11 shows the pin control for enabling
power-down.
Putting the TFA9812 into power-down is equivalent to enabling Sleep mode
(see
Section 8.2.2 ). This mode is entered immediately and no additional clock cycles are
required.
In order to prevent audible clicks, soft mute should be enabled at least T
d(soft_mute)
seconds before enabling Sleep mode.
The specified low current and power conditions in Table 1 are valid within 10
µ
s after
enabling Sleep mode.
8.4 Digital audio data input
8.4.1 Digital audio data format support
The TFA9812 supports a commonly used range of I 2 S and I 2 S-like digital audio data input
formats. These are listed in Table 12 .
Table 11. Power-up/power-down selection
Power-up pin
value Description
0 Power-down (Sleep mode)
1 Power-up
Table 12. Supported digital audio data formats
BCK frequency Interface format (MSB first) Supported in I 2 C
control mode
Supported in Legacy
control mode
32 f
s
I 2 S up to 16-bit data yes yes
32 f
s
MSB-justified 16-bit data yes yes
32 f
s
LSB-justified 16-bit data yes yes
48 f
s
I 2 S up to 24-bit data yes yes
48 f
s
MSB-justified up to 24-bit data yes yes