AD1954 Analog Devices, AD1954 Datasheet - Page 11

• Manufacturer Part Number: AD1954
• Description: SigmaDSP Digital Audio Processor
• Manufacturer: Analog Devices

DEEMP/SDATA_AUX—De-emphasis Input Pin/Auxiliary
serial data input. In de-emphasis mode, if this pin is asserted
HIGH, then a digital de-emphasis filter will be inserted into the
signal flow. The de-emphasis curve is valid only for a sample
rate of 44.1 kHz; curves for 32 kHz and 48 kHz may be pro-
grammed using the SPI port. This pin can also be used as an
auxiliary two-channel serial data input. This function is set by
writing a “1” to bit 11 of the Control Register. The same clocks
are used for this serial input as are used for the SDATA0, 1, 2
signals. This serial input can only be used in the signal processing
flow when using Analog Devices’ custom programming tools. The
use of de-emphasis is still available while this pin is used as a
serial input, but through the software rather than the hardware.
MUTE—Mute Output Signal.
When this pin is asserted HIGH, a ramp sequence is started that
gradually reduces the volume to zero. When deasserted, the
volume ramps from zero back to the original volume setting. The
ramp speed is timed so that it takes 10 ms to reach zero volume
when starting from the default 0 dB volume setting.
VOUTL+, VOUTL– —Left-Channel Differential Analog Outputs
Full-scale outputs correspond to 1 V
V
full-scale swing scales directly with VREF. These outputs are
capable of driving a load of > 5 kΩ, with a maximum peak cur-
rent of 1 mA from each pin. An external third-order filter is
recommended for filtering out-of-band noise.
VOUTR+, VOUTR– —Right Channel Differential Outputs.
Output characteristics are the same as for VOUTL+,
VOUTL– above.
VOUTS+, VOUTS– —SUB Channel Differential Outputs.
These outputs are designed to drive loads of 10 kΩ or greater,
with a peak current capability of 250 µA. This output does not
use digital interpolation, as it is intended for low-frequency
application. An external third-order filter with a cutoff frequency
< 2 kHz is recommended.
rms
differential, assuming a VREF input voltage of 2.5 V. The
PRELIMINARY TECHNICAL DATA
rms
on each output pin, or 2
VREFIN—Analog Reference Voltage Input.
The nominal VREFIN input voltage is 2.5 V; the analog gain
scales directly with the voltage on this pin. When using the
AD1954 to drive a power amplifier, it is recommended that the
VREFIN voltage be derived by dividing down and heavily filtering
the supply to the power amplifier. This provides a benefit if the
compressor/limiter in the AD1954 is used to prevent amplifier
clipping. In this case, if the DAC output voltage is scaled to the
amplifier power supply, a fixed compressor threshold can be used
to protect an amplifier whose supply may vary over a wide range.
any AC signal on this pin will cause distortion, and therefore a
large decoupling capacitor may be necessary to ensure that the
voltage on VREFIN is clean. The input impedance of VREFIN
is greater than 1 MΩ.
FILTCAP—Filter Cap Point.
This pin is used to reduce the noise on an internal biasing point,
in order to provide the highest performance. It may not be nec-
essary to connect this pin, depending on the quality of the layout
and grounding used in the application circuit.
DVDD—Digital VDD for Core.
5 V nominal.
ODVDD—Digital VDD for all digital outputs.
Variable from 2.7 V to 5.5 V.
DGND (2)—Digital Ground.
AVDD (2)—Analog VDD.
5 V nominal. For best results, use a separate regulator for
AVDD. Bypass capacitors should be placed close to the pins
and connected directly to the analog ground plane.
AGND—Analog Ground.
For best performance, separate non-overlapping analog and
digital ground planes should be used.
AD1954