Philips Semiconductors
Product specification
Advanced modem/audio analog front-end
UCB1200
48dB
24dB
0dB
21dB
0dB
24dB
48dB
programmed attenuation
Fig.5 Analog and digital attenuation settings audio output path.
69dB
The output level can be attenuated in 3 dB steps down to -69 dB. The first 8 attenuation steps (0 to 21 dB) are
implemented in the analog domain. The digital up sample filter contains a 24 dB and a 48 dB attenuation setting. This
arrangement preserves the resolution, thus the ‘audio quality’ of the audio output signal for attenuation settings till 21 dB.
The speaker driver is muted when AUDIO_MUTE in the audio control register B is set. The speaker driver will remain
activated in that case, however no signal is produced by the speaker driver circuit.
The speaker driver is designed to directly drive a bridge tied load (BTL). This yields the highest output power and this
arrangement does not require external DC blocking capacitors. The speaker driver also accepts single ended connection
of a speaker, in which case the maximum output power is reduced to a quarter of the BTL situation. Consequently this
way of connecting the speaker to the speaker driver reduces the power consumption of the speaker driver in the
UCB1200 by a factor of 2. Fig.6 shows possible ways to connect a speaker to the driver. Loading the amplifiers with a
capacitive load may cause high frequency oscillations and should be done cautiously.
1998 Jul 22
9
PHILIPS [ NXP SEMICONDUCTORS ]
