BC352239A Datasheet, PDF (95/116 Pages) List of Unclassifed Manufacturers – BlueCore 3-Multimedia External

Device Terminal Descriptions
8.8.26 Output Stage
The output digital circuitry converts the signal from 16-bit per sample, linear PCM of variable sampling frequency
to an 8 MBits/sec bit stream, which is fed into the analogue output circuitry.
The output circuit comprises a digital to analogue converter with gain setting and output amplifier. Its class-AB
output-stage is capable of driving a signal on both channels of up to 2V pk-pk- differential into a load of 32Ω and
500pF with a typical THD+N of -74dBc. The output is available as a differential signal between
AUDIO_OUT_N_LEFT and AUDIO_OUT_P_LEFT for the left channel as shown in Figure 8.32; and between
AUDIO_OUT_N_RIGHT and AUDIO_OUT_P_RIGHT for the right channel. The output is capable of driving a
speaker directly if its impedance is at least 16Ω if only one channel is connected or an external regulator is used.
AUDIO_OUT_P_LEFT
AUDIO_OUT_N_LEFT
Figure 8.32: Speaker Output (Left Channel Shown)
The gain of the output stage is controlled by a 3-bit programmable resistive divider, which sets the gain in steps
of approximately 3dB.
The single bit stream from the digital circuitry is low pass filtered by a second order bi-quad filter with a pole at
20kHz. The signal is then amplified in the fully differential output stage, which has a gain bandwidth of typically
1MHz. It uses its high open loop gain in the closed loop application circuit to achieve low distortion while
operating with low standing current.
8.9 I/O Parallel Ports
Fifteen lines of programmable bi-directional input/outputs (I/O) are provided. PIO[11:8] and PIO[3:0] are powered
from VDD_PIO. PIO[7:4] are powered from VDD_PADS. AIO [3:0] are powered from VDD_MEM.
PIO lines can be configured through software to have either weak or strong pull-ups or pull-downs. All PIO lines
are configured as inputs with weak pull-downs at reset.
PIO[0] and PIO[1] are normally dedicated to RXEN and TXEN respectively, but they are available for general
use.
Any of the PIO lines can be configured as interrupt request lines or as wake-up lines from sleep modes. PIO[6] or
PIO [2] can be configured as a request line for an external clock source. This is useful when the clock to
BlueCore3-Multimedia External is provided from a system application specific integrated circuit (ASIC).
BlueCore3-Multimedia External has four general purpose analogue interface pins, AIO[0], AIO[1], AIO[2] and
AIO[3]. These are used to access internal circuitry and control signals. One pin is allocated to decoupling for the
on-chip band gap reference voltage, the other three may be configured to provide additional functionality.
Auxiliary functions available via these pins include an 8-bit ADC and an 8-bit DAC. Typically the ADC is used for
battery voltage measurement. Signals selectable at these pins include the band gap reference voltage and a
variety of clock signals; 48, 24, 16, 8MHz and the XTAL clock frequency. When used with analogue signals the
voltage range is constrained by the analogue supply voltage (1.8V). When configured to drive out digital level
signals (clocks) generated from within the analogue part of the device, the output voltage level is determined by
VDD_MEM (1.8V).
BC352239A-ds-001Pc
© Cambridge Silicon Radio Limited 2004
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