AD1843JS Analog Devices Inc, AD1843JS Datasheet - Page 13

• Manufacturer Part Number: AD1843JS
• Description: IC CODEC STEREO 5V 16BIT 80PQFP
• Manufacturer: Analog Devices Inc
• Type: Stereo Audior

Specifications of AD1843JS

• Rohs Status: RoHS non-compliant
• Data Interface: Serial
• Resolution (bits): 16 b
• Number Of Adcs / Dacs: 1 / 2
• Sigma Delta: Yes
• S/n Ratio, Adcs / Dacs (db) Typ: 92 / 86
• Dynamic Range, Adcs / Dacs (db) Typ: 85 / 80
• Voltage - Supply, Analog: 4.75 V ~ 5.25 V
• Voltage - Supply, Digital: 2.85 V ~ 5.25 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 80-MQFP, 80-PQFP

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On-chip bit and baud clock generation circuitry allows either
synchronous or asynchronous operation of the transmit (DAC)
and receive (ADC) paths. Each path features independent
phase advance and retard adjustments via software control. The
AD1843 can also synchronize modem operation to an external
terminal band clock. Because the device has multiple input and
output channels and converters, it is well suited for telephony
applications requiring multiple channels for voice and modem.
A detailed block diagram of the AD1843 is shown in Figure 2.
DETAILED PRODUCT DESCRIPTION
The Serial-Port AD1843 SoundComm Codec integrates the key
audio and PSTN data conversion and control functions into a
single integrated circuit. The AD1843 is intended to provide a
complete, single-chip audio and fax/modem solution for PC
multimedia applications.
External circuit requirements are limited to a minimal number
of low cost support components. Dynamic range exceeds 80 dB
over the 20 kHz audio band. Sample rates from 4 kHz to
54 kHz with 1 Hz resolution are supported from a single exter-
nal crystal or clock source.
The AD1843 SoundComm Codec is intended to be interfaced
through a DSP chip or an ASIC to a host bus such as ISA,
EISA or PCI. A general system architecture is shown in
Figure 3.
The SoundComm codec includes a stereo pair of
digital converters and two stereo pairs of
converters. Inputs to the ADC can be selected from eight
sources of analog signals: stereo line (LIN), stereo microphone
(MIC), stereo auxiliary line #1 (AUX1), stereo auxiliary line #2
(AUX2), stereo auxiliary line #3 (AUX3), mono line (MIN),
mixer output, and DAC2 output. A mono output and a stereo
headphone driver are included on-chip. A stereo line level input
(SUM) can be mixed into the output summer. A software-con-
trolled programmable gain stage allows independent gain for
each ADC channel. The ADCs’ output can be digitally mixed
with both the DAC1 and DAC2 inputs. The left and right
ADC channels can be configured for different sample rates and
digital filter function (audio, modem or resampling).
The pair of 16-bit outputs from the ADCs is available over a se-
rial interface that also supports 16-bit digital input to the DACs
and control/status information. The AD1843 can accept and
generate 16-bit twos-complement PCM linear digital data, 8-bit
unsigned magnitude PCM linear data, and 8-bit -law or A-law
companded digital data. The data format is defined indepen-
dently for each conversion resource on the AD1843.
The
and a digital interpolation filter. The DAC1 and DAC2 outputs
can be mixed in the digital domain. Digital and analog attenua-
tors provide independent user volume control (plus mute) over
each DAC channel. Nyquist images and shaped quantized
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DACs are preceded by a four sample deep FIFO buffer
ASIC
Figure 3. AD1843 System Diagram
ADSP-21xx
AD1843
digital-to-analog
ANALOG I/O
analog-to-
–13–
noise are removed from the DACs’ analog stereo output by on-
chip switched-capacitor and continuous-time filters. All of the
analog inputs (except the stereo line input) can be mixed with
the DAC1 output in the analog domain. The DAC2 output can
also be mixed with the DAC1 output in the analog domain.
The DAC1 and DAC2 digital data can be fed back to the digital
half of the ADC to enable digital resampling operation. DAC1
and DAC2 can be run at different sample rates and with differ-
ent digital filter functions, without any beat frequency problems.
FUNCTIONAL DESCRIPTION
This section overviews the functionality of the AD1843 and is
intended as a general introduction to the capabilities of the de-
vice. As much as possible, detailed reference information has
been placed in “Control Registers” and other sections. The
user is not expected to refer repeatedly to this section.
Analog Inputs
The AD1843 SoundComm Codec accepts stereo line-level and
mic-level inputs. The mono MIN analog signal input, and LIN
(differential), MIC, AUX1, AUX2, AUX3 and post-mixed
DAC output analog stereo signals are multiplexed to the inter-
nal programmable gain amplifier stage (PGA).
The PGA following the input multiplexer allows left and right
independent selectable gains for each channel from 0 dB to
22.5 dB in +1.5 dB steps. The Codec can operate either in a
global stereo mode or in a global mono mode with left-channel
inputs appearing at both channel outputs.
Analog Mixing
The MIN analog mono signal, and the MIC, AUX1, AUX2,
AUX3 and SUM analog stereo signals can be mixed in the ana-
log domain with the DAC1 output. Each channel of each auxil-
iary analog input can be independently gained/attenuated from
+12 dB to –34.5 dB in 1.5 dB steps or completely muted. The
mixer output is available on LOUT1 externally and as an input
to the ADCs. Even if the AD1843 is not playing back data from
its DACs, the analog mix function can still be active.
MIN allows the analog signal intended for the PC speaker to be
passed through, attenuated or mixed in the AD1843’s analog
domain. MIN can be used to accept other mono input sources.
A digital control signal pin PDMNFT (Power Down Mono
Feed Through) enables the mono input signal to be fed through
to the mono output when the AD1843 mixer is powered down.
Analog-to-Digital Datapath
The AD1843
A single pole of passive filtering is all that is required for
antialiasing the analog input because of the ADC’s high over-
sampling ratio. The ADCs include linear-phase digital decima-
tion filters that low-pass filter the input. ADC input overrange
conditions will cause bits to be set that can be read.
Each channel of the mic inputs can be amplified in the analog
domain by +20 dB to compensate for the voltage swing differ-
ence between line levels and typical condenser microphone levels.
Digital-to-Analog Datapath
The
a low-pass digital interpolation filter. The anti-imaging interpo-
lation filter oversamples and digitally filters the higher frequency
images. The attenuator allows independent control of each
DAC channel from +12.0 dB to –82.5 dB in 1.5 dB steps plus
full mute. The DACs’
vert the signal to a single-bit stream. The DAC outputs are then
DACs are preceded by a programmable attenuator and
ADCs incorporate a fourth-order modulator.
noise shapers oversample and con-
AD1843