TDA8594 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 5 — 11 June 2013 6 of 49
NXP Semiconductors
TDA8594
I
2
C-bus controlled 4 50 W power amplifier
7.2 Output stage
The output stage of each amplifier channel consists of two PMOS power transistors and
two NMOS transistors in a BTL configuration. The process used is the BCDMOS process
with an isolated substrate, Silicon On Insulator (SOI) process, which has almost no
parasitic components and therefore prevents latch-up.
7.3 Distortion (clip) detection
If the output of the amplifier starts clipping to the supply voltage or to ground, the output
will become distorted. If the distortion per channel exceeds a selectable threshold (2 %,
5 % or 10 %), one of the two diagnostic pins (DIAG pin or STB pin) will be activated. To be
able to detect if, for instance, the front channels (channel 1 and channel 3) or rear
channels (channel 2 and channel 4) are clipping, the clip information can be directed per
channel to the DIAG pin or the STB pin. It is possible to have only the clip information on
the diagnostic pins by disabling the temperature and load information on the DIAG pin. In
this mode the temperature and load protection are still functional but can only be read via
the I
2
C-bus.
7.4 Output protection and short-circuit operation
When a short-circuit to ground, V
P
or across the load occurs on one or more outputs of an
amplifier, only the amplifier with the short-circuit is switched off. The channel that has a
short-circuit and the type of short-circuit can be read-back via the I
2
C-bus. If the DIAG pin
is enabled for load fault information (IB2[D4] = 0) the DIAG pin will be pulled LOW. After
16 ms the amplifier will be switched on again and, if the short-circuit conditions still occur,
the amplifier will be switched off.
The 16 ms cycle will reduce the dissipation. To prevent audible distortion, the amplifier
channel with the short-circuit can be disabled via the I
2
C-bus.
7.5 SOAR protection
The output transistors are protected by Safe Operating ARea (SOAR) protection. The
TDA8594 has a two-stage SOAR protection:
• If the differential output voltage across the load is less than 1 V, and the current
through the load is more than 4 A, the amplifier channel will be switched off for 16 ms.
To prevent incorrect switch-off with an inductive load or very high input signals, the
condition (V
o
< 1 V and I
L
> 4 A) must exist for more than 300 s.
• If the differential output voltage across the load is more than 1 V, and the current
through the load is more than 8 A, the amplifier channel will be switched off for 16 ms.
7.6 Speaker protection
To prevent damage of the speaker when one side of the speaker is connected to ground,
a missing current protection is implemented. When in one channel the current in the high
side power is not equal to the current in the low side power, a fault condition is assumed
and the channel will be switched off. The speaker protection will be activated under the
following conditions:
• V
o
< 1.75 V and I
missing(det)
>1A for 80s
• V
o
> 1.75 V and I
missing(det)
>3A for 80s
