UMA1021M/C2 Philips Semiconductors (Acquired by NXP), UMA1021M/C2 Datasheet - Page 16

• Manufacturer Part Number: UMA1021M/C2
• Description: UDA1380; Stereo Audio Coder-decoder For MD, CD And MP3
• Manufacturer: Philips Semiconductors (Acquired by NXP)

Philips Semiconductors
8.6
8.6.1
The Filter-Stream Digital-to-Analog Converter (FSDAC) is
a semi-digital reconstruction filter that converts the
1-bit data stream (running at either 64f
noise shaper or 128f
noise shaper into an analog output voltage. The filter
coefficients are implemented as current sources, and are
summed at virtual ground of the output operational
amplifier. In this way very high signal-to-noise
performance and low clock jitter sensitivity are achieved.
A post-filter is not needed due to the inherent filter function
of the DAC. On-board amplifiers convert the FSDAC
output current to an output voltage signal, capable of
driving a line output. The output voltage of the FSDAC
scales proportionally with the power supply voltage.
Remark: When the FSDAC is powered-down, the output
of the FSDAC becomes high impedance.
8.6.2
The FSDAC has a mixer input, which makes it possible to
mix an analog signal to the output signal of the FSDAC
itself. In schematic form this is given in Fig.9.
This mixer input can be used for instance for mixing-in a
GSM signal or an FM signal directly to the line output.
In the UDA1380, the mixer input is connected from the
ADC line input via an AVC unit.
Remark: Before the AVC unit can be used stand-alone,
meaning without the digital part running, first the DAC part
must be initialised in order to have the DAC output
generating zero current. Otherwise the signal will be
clipped.
2003 Apr 04
handbook, halfpage
Stereo audio coder-decoder
for MD, CD and MP3
Fig.9
FSDAC
bitstream
G
A
NALOG MIXER INPUT
ENERAL INFORMATION
Mixing signals to the FSDAC output
(analog domain).
s
FSDAC
for the 3rd-order noise shaper) of the
to analog mixer input
s
for the 5th-order
MGU531
16
8.7
The UDA1380 is equipped with a headphone driver which
can deliver 35 mW (at 3.0 V power supply) into a 16
load.
The headphone driver does not need external
DC decoupling capacitors because it can be DC coupled
with respect to a special headphone output reference
voltage. This saves two external capacitors (which is quite
useful in a portable device).
The headphone driver is equipped with short-circuit
protection on all three operational amplifiers (left, right and
the virtual ground). Each of the operational amplifiers has
a signalling bit which becomes logic 1 in case the limiter is
activated, for instance in case of a short-circuit. This
means the microcontroller in the system can poll the
L3-bus or I
soon as (and for as long as) the short-circuit detection bits
are activated, the microcontroller can signal the user that
something is wrong or power-down the headphone driver
(for instance, for energy-saving purposes).
Remark: To improve headphone channel separation
performance, the distance between V
speaker port must be minimized.
8.8
8.8.1
The ADC output signal and digital input signal can be
mixed without external DSP as shown in Fig.10. This mixer
can be controlled via the microcontroller interface, and
must only be enabled when the ADC and the DAC are
running at the same frequency. In addition, the mixer
output signal can also be applied to the I
interface.
Headphone driver
Digital and analog mixers (DAC)
D
IGITAL MIXER
2
C-bus register of the headphone driver and as
REF(HP)
Product specification
UDA1380
2
S-bus output
and the micro