TDA8594 Datasheet, PDF (7/48 Pages) NXP Semiconductors – I2C-bus controlled 4 X 50 W power amplifier

NXP Semiconductors
TDA8594
I²C-bus controlled 4 × 50 W power amplifier
7.7 Standby and mute operation
The function of the STB pin is different in legacy mode and I²C-bus mode.
7.7.1 Legacy mode (pin ADSEL connected to ground)
The function of the STB pin will change from standby/operating to standby/mute/operating
and the amplifier will start directly when the STB is put into mute or operating mode. Mute
operating is controlled via an internal timer (20 ms) to minimize mute-on pops. When the
STB pin is switched directly from operating to standby, first the fast mute will be activated
(switching to mute within 100 µs) and then the amplifier will shut-down.
7.7.2 I²C-bus mode
When the STB pin is LOW, the total quiescent current is low, and the I²C-bus lines will not
be loaded.
When the STB pin is switched HIGH, the TDA8594 is put in operating condition and will
perform a Power-On Reset (POR), which results in a LOW level DIAG pin. The TDA8594
will start up when instruction bit IB1[D0] is set. Bit D0 will also reset the ‘power-on reset
occurred’ bit (DB2[D7]) and releases the DIAG pin.
The soft mute and fast mute can be activated via the I²C-bus. The soft mute can be
activated independently for the front channels (channel 1 and channel 3) and rear
channels (channel 2 and channel 4), and mutes the audio in 20 ms. The fast mute
activates the mute for all channels at the same time and mutes the audio in 0.1 ms.
Releasing the mute after a fast mute will be by a soft un-mute of approximately 20 ms.
When the STB pin is switched to Standby mode and the amplifier has started, first the fast
mute will be activated and then the amplifier will shut-down. For instance, during an
engine start, it is possible to fully mute the amplifiers within 100 µs by switching the STB
pin to zero.
7.8 Start-up and shut-down sequence
To prevent the amplifier producing switch-on or switch-off pop noise, the capacitor on the
SVR pin is used for smooth start-up and shut-down. Increasing the value of the SVR
capacitor will mean a longer start-up and shut-down time. The amplifier output voltage is
charged to half the supply voltage minus 1.4 V in mute condition, independent of the
I²C-bus mute settings in I²C-bus mode or STB voltage in legacy mode. The last 1.4 V,
where the output will reach half the supply voltage, is used to release the mute if the
I²C-bus bits were set to mute off (IB2[D2:D0] = 000; V_STB > 6.5 V in legacy mode), or will
stay in mute when the bits were set to mute (2.6 V < V_STB < 4.5 V in legacy mode).
When the amplifier is switched off by pulling the STB pin LOW, the amplifier is first muted
(fast mute) and then the capacitor on the SVR pin is discharged. With an SVR capacitor of
22 µF, the standby current has reached 1 second after the STB pin is switched to zero
(see Figure 3, Figure 4, Figure 5 and Figure 6).
The start-up and shut-down pop can be further decreased by activating the low pop mode.
When the low pop mode is enabled (IB2[D3] = 0), the output voltage rise from ground level
during start-up will be slower (see Figure 5). This will decrease the pop even more but will
increase the start-up time.
TDA8594_2
Product data sheet
Rev. 02 — 11 December 2007
© NXP B.V. 2007. All rights reserved.
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