TDA8920 Datasheet, PDF (5/16 Pages) NXP Semiconductors – 2 x 50 W class-D power amplifier

Philips Semiconductors
2 × 50 W class-D power amplifier
Preliminary specification
TDA8920
FUNCTIONAL DESCRIPTION
The TDA8920 is a multi purpose audio power amplifier in
class-D technology. It contains two independent amplifiers
with high output power, high efficiency (90%), low
distortion and a low quiescent current. The amplifiers can
be connected in the following configurations:
• Mono bridge-tied load amplifier
• Stereo single-ended amplifiers.
The amplifier can be switched in three operating modes
with the mode select input:
• Standby mode, with a very low supply current
(practically zero)
• Mute mode; the amplifiers are operational but the audio
signal at the output is suppressed
• Operating mode (amplifier fully operational) with output
signal.
For suppressing plop noise the amplifier will remain
automatically for approximately 500 ms in the mute
mode before switching to operating mode. During this
time the coupling capacitors at the input are fully
charged. An example of a switching circuit for driving the
mode select input is illustrated in Fig.3.
Pulse Width Modulation (PWM) frequency
The output signal of the amplifier is a PWM signal with a
sample frequency of 500 kHz. The use of a second order
LC filter in the application results in an analog audio signal
across the loudspeaker. This switching frequency is fixed
by an external resistor R_OSC connected between pin OSC
and pin SGND. With the resistor value given in the
application diagram, the oscillating frequency is typical
500 kHz. The oscillator frequency can be calculated using:
Current limiting
With an external resistor R_LIM connected between pin LIM
and V_SS the maximum output current of the amplifiers can
be set. If pin LIM is short-circuited to V_SS, then the
maximum output current is limited to 7 A. The relationship
between maximum output current and resistor value is
given by:
I_O(max)
=
-------------7----0---.--1---0---³-------------- [A]


10.10³
+
R_{LIM}
Protections
Protections are included to avoid the device being
damaged at:
• Over-temperature T_j > 150 °C
• Short-circuit of the loudspeaker terminals: when
short-circuited the power dissipation is limited
• A maximum current limiter which limits the maximum
output current to 7 A, or to the value set by R_LIM. During
limiting the current is measured and when the current is
higher than 7 A, the amplifier is switched off within 3 µs
and every 20 ms the IC tries to restart. The dissipation
will be low because of this low duty cycle.
• ESD protection (human body model: 3000 V and
machine model: 300 V).
handbook, halfpage ^{+5 V}
f_osc = ^5-R---.-_O-1---_S^0---_C9- [ Hz]
If two or more devices are used in the same audio system
it is advised to have both devices working on the same
oscillation frequency. This can be realized by connecting
all OSC pins together.
standby/on
mute
R
pin MODE
R
SGND
MGR660
Fig.3 Mode select input drive circuit.
1998 Dec 01
5