TDA8580J Datasheet, PDF (16/28 Pages) NXP Semiconductors – Multi-purpose power amplifier

Philips Semiconductors
Multi-purpose power amplifier
Preliminary specification
TDA8580J
APPLICATION INFORMATION
The application circuit depends on the supply voltage
used. For supply voltages below 18 V the application
circuits are shown in Figs 28, 29 and 30.
The typical application circuits for the different supply
voltage ranges are shown in Figs 31, 32 and 33.
Additional information for the applications shown in
Figs 28, 29 and 30
The RC-network connected to pin 5 determines the
amplifier switch on/off behaviour as follows;
• Switched from STANDBY to MUTE when V_switching
(typically 9 V) is enabled and the switch SW1 is closed.
During MUTE there is no output noise and no offset.
• Switched from MUTE to ON when the switch SW1 is
opened. During switching ON the offset and noise are
gradually built up. The time constant is fixed by R1 × C1.
The inputs can be tied together and connected to one input
capacitor. Because the input resistance is decreased by a
factor of 2, the low frequency roll-off is shifted to a higher
frequency when C_i is kept the same value.
The low frequency cut-off is determined by;
f_–3dB = 1 ⁄ (2π × R_i × C_i )
= _2----π-----_×-----6---0-----_×-----1---0----₃^1----_×-----2---2---0-----_×-----1---0----_–--₉- = 12 Hz.
The Boucherot network connected to the buffer (pin 9) is
necessary to guarantee a low output resistance at high
frequencies when the buffer is loaded (only in SE
applications).
Additional information for the applications shown in
Figs 31, 32 and 33
Short circuit behaviour at high supply voltages (V_p > 18 V):
• When V_p > 18 V it is advisable to use the applications
given in Figs 32 and 33. In these applications the
diagnostics output is tied to pin 5 (one pin operation) or
pin 13 (two pin operation). During a fault condition the
amplifier is soft-muted and the amplitude of the output
signal is reduced at:
– over temperature (still large dynamic range)
– short to ground and over load (output current
reduced)
• The 4.7 µF capacitor and the 10 kΩ resistor connected
to pin 5 or to pin 13 are used to:
– provide a stable loop
– control the switch on/off behaviour
– minimize the effect due to clip detection.
Use of common buffer
In SE applications the buffer output is used in place of a
SE capacitor. To minimize the crosstalk (high channel
separation) and distortion it is advised to connect the
speaker wires as closely as possible to pin 9 without using
a shared wire. Internally in the IC all the efforts have been
taken to minimize the crosstalk by locating the feedback
loops as close as possible to pin 9.
If a common wire is shared by all the speakers, the series
resistance of this shared wire will introduce added signal
voltages resulting from the currents flowing through this
wire when a connected amplifier is driven by a signal.
Optimize the THD performance
The TDA8580J application can be optimized to gain the
lowest THD possible by applying the following guidelines:
• SE application: minimize the shared wires to pin 9 (see
section “Use of common buffer”).
• Because the inputs are quasi differential, ground loops
can be avoided by connecting the negative terminal of
the 100 µF signal ground capacitor (connected to
pin 12) to the ground pin of the signal processor.
Note: do not leave the inputs in the open condition to
prevent HF oscillation.
• Increase the value of electrolytic supply capacitor
(typical value 1000 µF) to the maximum possible to
minimize cross talk and distortion at low signal
frequencies, due to the PSRR (power supply rejection
ratio). For suppressing high frequency transients on the
supply line a capacitor (typical value 100 nF) with a low
ESR is required to be connected in parallel with the
electrolytic capacitor. The capacitor combination must
be placed as close as possible to the IC (using short
interconnection tracks).
Headroom
A typical CD requires at least 12 dB dynamic headroom
(a factor of 15.85), compared with the average power
output, for passing the loudest parts without distortion.
2000 Apr 18
16