TDA8552T_02 Datasheet, PDF (6/27 Pages) NXP Semiconductors – 2 x 1.4 W BTL audio amplifiers with digital volume control and headphone sensing

NXP Semiconductors
2 x 1.4 W BTL audio amplifiers with digital
volume control and headphone sensing
Product specification
TDA8552T; TDA8552TS
FUNCTIONAL DESCRIPTION
The TDA8552T is a 2 × 1.4 W BTL audio power amplifier
capable of delivering 2 × 1.4 W output power into an 8 Ω
load at THD = 10% using a 5 V power supply. The gain of
the amplifier can be set by the digital volume control.
The gain in the maximum volume setting is 20 dB (low
gain) or 30 dB (high gain). This maximum gain can be
selected by the gain selection pin. The headphone sense
input (HPS) can be used to detect if a headphone is
plugged into the jack connector. If a headphone is plugged
into the jack connector the amplifier switches from the BTL
to the SE mode and the BTL loudspeakers are switched
off. This also results in a reduction of quiescent current
consumption. Using the MODE pin the device can be
switched to the standby condition, the mute condition or
the normal operating condition. The device is protected by
an internal thermal shutdown protection mechanism.
Power amplifier
The power amplifier is a Bridge-Tied Load (BTL) amplifier
with a complementary CMOS output stage. The total
voltage loss for both output power MOS transistors is
within 1 V and with a 5 V supply and an 8 Ω loudspeaker
an output power of 1.4 W can be delivered. The total gain
of this power amplifier can be set at 20 or 30 dB by the gain
selection pin.
Gain selection
The gain selection can be used for a fixed gain setting,
depending on the application. The gain selection pin must
be hard wired to ground (20 dB) or to V_DD (30 dB). Gain
selecting during the operation is not advised, switching is
not guaranteed plop free.
Input attenuator
The volume control operates as a digitally controlled input
attenuator between the audio input pin and the power
amplifier. In the maximum volume control setting the
attenuation is 0 dB and in the minimum volume control
setting the typical attenuation is 80 dB. The attenuation
can be set in 64 steps by the UP/DOWN pin. Both
attenuators for channels 1 and 2 are separated from each
other and are controlled by there own UP/DOWN pin.
Balance control can be arranged by applying UP/DOWN
pulses only on pins 6 and 7, see Fig.5.
Volume control
Each attenuator is controlled with its own UP/DOWN pin
(trinary input):
• Floating UP/DOWN pin: volume remains unchanged
• Negative pulses: decreasing volume
• Positive pulses: increasing volume.
Each pulse on the UP/DOWN pin results in a change in
gain of ^8----0-- = 1.25 dB (typical value).
64
In the basic application the UP/DOWN pin is switched to
ground or V_DD by a double push-button. When the supply
voltage is initially connected, after a complete removal of
the supply, the initial state of the volume control is an
attenuation of 40 dB (low volume), so the gain of the total
amplifier is −20 dB in the low gain setting or −10 dB in the
high gain setting. After powering-up, some positive pulses
have to be applied to the UP/DOWN pin for turning up to
listening volume.
Auto repeat
If the UP/DOWN pin is LOW or HIGH for the wait time (t_wait
in seconds) (one of the keys is pressed) then the device
starts making up or down pulses by itself with a frequency
given by ---1---- (repeat function).
t_rep
The wait time and the repeat frequency are set using an
internal RC oscillator with an accuracy of ±10%.
Volume settings in standby mode
When the device is switched with the MODE select pin to
the mute or the standby condition, the volume control
attenuation setting keeps its value, under the assumption
that the voltage on the V_DD pin does not fall below the
minimum supply voltage. After switching the device back
to the operation mode, the previous volume setting is
maintained. In the standby mode the volume setting is
maintained as long as the minimum supply voltage is
available. The current consumption is very low,
approximately 1 μA (typ.). In battery fed applications the
volume setting can be maintained during battery exchange
if there is a supply capacitor available.
2002 Jan 04
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