821024J Integrated Device Technology (Idt), 821024J Datasheet - Page 5

• Manufacturer Part Number: 821024J
• Description: Audio Codec 4ADC / 4DAC 32-Pin PLCC
• Manufacturer: Integrated Device Technology (Idt)
• Type: PCMr

Specifications of 821024J

• Package: 32PLCC
• Number Of Channels: 4ADC /4 DAC
• Number Of Dacs: 4
• Operating Supply Voltage: 5 V

IDT821024 QUAD NON-PROGRAMMABLE PCM CODEC
FUNCTIONAL DESCRIPTION
filters. It provides the four-wire solution for the subscriber line circuitry in
digital switches. The device converts analog voice signal to digital PCM
data, and converts digital PCM data back to analog signal. Digital filters
are used to bandlimit the voice signals during the conversion. Either A-law
or -law is supported by the IDT821024. The law selection is performed
by A/ pin.
MHz, or 8.192 MHz. Internal circuitry determines the master clock frequency
automatically.
DX and DR. The time slots of the four channels are determined by the
individual Frame Sync signals at rates from 256 kHz to 8.192 MHz. For
each channel, the IDT821024 provides a transmit Frame Sync signal and
a receive Frame Sync signal.
to save power consumption. The Channel Power Down Pins PDN1-4
configure channels to be active (power-on) or standby (power-down)
separately.
Signal Processing
Digital-to-Analog Converters (DAC) are used in the IDT821024 to provide
the required conversion accuracy. The associated decimation and interpo-
lation filtering are realized with both dedicated hardware and Digital Signal
Processor (DSP). The DSP also handles all other necessary functions such
as PCM bandpass filtering and sample rate conversion.
Transmit Signal Processing
converted into digital data. The digital output of the oversampling ADC is
decimated and sent to the DSP. The transmit filter is implemented in the
DSP as a digital bandpass filter. The filtered signal is further decimated
The IDT821024 contains four channel PCM CODEC with on chip digital
The frequency of the master clock (MCLK) can be 2.048 MHz, 4.096
The serial PCM data for four channels are time multiplexed via two pins,
Each channel of the IDT821024 can be powered down independently
High performance oversampling Analog-to-Digital Converters (ADC) and
In the transmit path, the analog input signal is received by the ADC and
SLIC
SLIC
VTX
RSN
to
to
Figure 1. IDT821024 Transmit Gain Setting for Channel 1
R
R
TX
RX
1
1
Net
Bal
C
C
RX
TX
1
1
V
V
IN
OUT
1
1
5
and compressed to PCM format.
Transmit PCM Interface
DX pin every 125 s. The transmit logic, synchronized by the Transmit
Frame Sync signal (FSXn), controls the data transmission. The FSXn
pulse identifies the transmit time slot of the PCM frame for Channel N.
The PCM Data is transmitted serially on DX pin with the Most Significant
Bit (MSB) first. When the PCM data is being output on DX pin, the TSC
signal will be pulled low.
Receive Signal Processing
per second. The PCM code is expanded and sent to the DSP for
interpolation. A receive filter is implemented in the DSP as a digital lowpass
filter. The filtered signal is then sent to an oversampling DAC. The DAC
output is post-filtered and delivered at VOUT pin by an amplifier. The
amplifier can drive resistive load higher than 2 K .
Receive PCM Interface
every 125 s. The receive logic, synchronized by the Receive Frame Sync
signal (FSRn), controls the data receiving process. The FSRn pulse
identifies the receive time slot of the PCM frame for Channel N. The PCM
Data is received serially on DR pin with the Most Significant Bit (MSB)
first.
Hardware Gain Setting In Transmit Path
resistors, R
ing equation:
IDT821024
The transmit PCM interface clocks out 1 byte (8 bits) PCM data out of
In the receive path, the PCM code is received at the rate of 8,000 samples
The receive PCM interface clocks 1 byte (8 bits) PCM data into DR pin
The transmit gain of the IDT821024 for each channel can be set by 2
The receive gain of IDT821024 is fixed and equal to 1.
I
A/D
V
REF
D/A
REF
REF
V
I
REF
REF
to
and R
TXn
I
V
REF
REF
(as shown in Figure 1), according to the follow-
1
1
INDUSTRIAL TEMPERATURE RANGE
G
R
C
t
REF
FIL
1
3
R
R
TXn
REF