Texas Instruments TLC32045EFN, TLC32045CN, TLC32045CFN, TLC32044MJB, TLC32044MJ Datasheet

TLC32044C, TLC32044E, TLC32044I, TLC32044M, TLC32045C, TLC32045I

VOICE-BAND ANALOG INTERFACE CIRCUITS

SLAS017F – MARCH 1988 – REVISED MA Y 1995

1

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

D

14-Bit Dynamic Range ADC and DAC

D

2’s Complement Format

D

Variable ADC and DAC Sampling Rate Up
to 19,200 Samples per Second

D

Switched-Capacitor Antialiasing Input Filter
and Output-Reconstruction Filter

D

Serial Port for Direct Interface to
TMS(SMJ)320C17, TMS(SMJ)32020,
TMS(SMJ)320C25,
and TMS320C30 Digital Signal Processors

D

Synchronous or Asynchronous ADC and
DAC Conversion Rates With Programmable
Incremental ADC and DAC Conversion
Timing Adjustments

D

Serial Port Interface to SN74(54)299
Serial-to-Parallel Shift Register for Parallel
Interface to TMS(SMJ)32010,
TMS(SMJ)320C15, or Other Digital
Processors

D

Internal Reference for Normal Operation
and External Purposes, or Can Be
Overridden by External Reference

D

CMOS Technology

description

The TLC32044 and TLC32045 are complete
analog-to-digital and digital-to-analog input and
output systems on single monolithic CMOS chips.
The TLC32044 and TLC32045 integrate a
bandpass switched-capacitor antialiasing input
filter, a 14-bit-resolution A/D converter, four
microprocessor-compatible serial port modes, a
14-bit-resolution D/A converter, and a low-pass
switched-capacitor output-reconstruction filter.
The devices offer numerous combinations of
master clock input frequencies and conversion/
sampling rates, which can be changed via digital
processor control.

Copyright  1995, Texas Instruments Incorporated

PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

1
2
3
4
5
6
7
8
9
10
11
12
13
14

28
27
26
25
24
23
22
21
20
19
18
17
16
15

NU

RESET

EODR

FSR

DR

MSTR CLK

V

DD

REF
DGTL GND
SHIFT CLK

EODX

DX

WORD/BYTE

FSX

NU
NU
IN+
IN–
AUX IN+
AUX IN–
OUT+
OUT–
V

CC+

V

CC–

ANLG GND
ANLG GND
NU
NU

J† OR N PACKAGE

(TOP VIEW)

32 1

13 14

5

6

7

8

9

10

11

IN–
AUX IN+
AUX IN–
OUT+
OUT–
V

CC+

V

CC–

DR

MSTR CLK

V

DD

REF
DGTL GND
SHIFT CLK

EODX

4

15 16 17 18

WORD/BYTE

FSX

NU

NU

ANLG GND

ANLG GND

FSR

EODR

RESET

NU

28 27 26

25
24
23
22
21
20
19

12

DX

NU

IN +

NU

NU – Nonusable; no external connection should be made to
these terminals (see Table 2).

FK OR FN PACKAGE

(TOP VIEW)

†

Refer to the mechanical data for the JT package.

TLC32044C, TLC32044E, TLC32044I, TLC32044M, TLC32045C, TLC32045I
VOICE-BAND ANALOG INTERFACE CIRCUITS

SLAS017F – MARCH 1988 – REVISED MA Y 1995

2

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

AVAILABLE OPTIONS

PACKAGE

T

A

PLASTIC CHIP

CARRIER

(FN)

PLASTIC DIP

(N)

CERAMIC DIP

(J)

CHIP CARRIER

(FK)

°

°

TLC32044CFN TLC32044CN

0°C to 70°C

TLC32045CFN TLC32045CN

–20°C to 85°C TLC32044EFN

°

°

TLC32044IN

–

40°C to 85°C

TLC32045IN

–55°C to 125°C TLC32044MJ TLC32044MFK

description (continued)

Typical applications for the TLC32044 and TLC32045 include speech encryption for digital transmission,
speech recognition/ storage systems, speech synthesis, modems (7.2-, 8-, 9.6-, 14.4-, and 19.2-kHz sampling
rate), analog interface for digital signal processors (DSPs), industrial process control, biomedical
instrumentation, acoustical signal processing, spectral analysis, data acquisition, and instrumentation
recorders. Four serial modes, which allow direct interface to the TMS(SMJ)320C17, TMS(SMJ)32020,
TMS(SMJ)320C25, and TMS(SMJ)320C30 digital signal processors, are provided. Also, when the transmit and
receive sections of the analog interface circuit (AIC) are operating synchronously, it will interface to two
SN74(54)299 serial-to-parallel shift registers. These serial-to-parallel shift registers can then interface in
parallel to the TMS(SMJ)32010, TMS(SMJ)320C15, and other digital signal processors, or external FIFO
circuitry . Output data pulses are emitted to inform the processor that data transmission is complete or to allow
the DSP to differentiate between two transmitted bytes. A flexible control scheme is provided so that the
functions of the TLC32044 or TLC32045 can be selected and adjusted coincidentally with signal processing via
software control.

The antialiasing input filter comprises eighth-order and fourth-order CC-type (Chebyshev/elliptic transitional)
low-pass and high-pass filters, respectively. The input filter is implemented in switched-capacitor technology
and is preceded by a continuous time filter to eliminate any possibility of aliasing caused by sampled data
filtering. When only low-pass filtering is desired, the high-pass filter can be switched out of the signal path. A
selectable, auxiliary , dif ferential analog input is provided for applications where more than one analog input is
required.

The A/D and D/A architectures ensure no missing codes and monotonic operation. An internal voltage reference
is provided to ease the design task and to provide complete control over the performance of the TLC32044 or
TLC32045. The internal voltage reference is brought out to a terminal and is available to the designer. Separate
analog and digital voltage supplies and grounds are provided to minimize noise and ensure a wide dynamic
range. Also, the analog circuit path contains only differential circuitry to keep noise to an absolute minimum.
The only exception is the DAC sample and hold, which utilizes pseudo-differential circuitry.

The output-reconstruction filter is an eighth-order CC-type (Chebyshev/elliptic transitional low-pass filter)
followed by a second-order (sin x)/x correction filter and is implemented in switched-capacitor technology . This
filter is followed by a continuous-time filter to eliminate images of the digitally encoded signal. The on-board
(sin x)/x correction filter can be switched out of the signal path using digital signal processor control, if desired.

The TLC32044C and TLC32045C are characterized for operation from 0°C to 70°C. The TLC32044E is
characterized for operation from –20°C to 85°C. The TLC32044I and TLC32045I are characterized for
operation from –40°C to 85°C. The TLC32044M is characterized for operation from –55°C to 125°C.

TLC32044C, TLC32044E, TLC32044I, TLC32044M, TLC32045C, TLC32045I

VOICE-BAND ANALOG INTERFACE CIRCUITS

SLAS017F – MARCH 1988 – REVISED MA Y 1995

3

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

functional block diagram

M
U
X

M
U
X

IN+
IN–

AUX IN +
AUX IN –

Internal
Voltage

Reference

SHIFT CLK

MSTER CLK

EODR

DR

FSR

WORD/BYTE
DX
FSX
EODX

SERIAL

PORT

A/D

OUT+
OUT–

M
U
X

D/A

sin x/x

Correction

Filter

Filter

Transmit Section

V

CC+VCC–

ANLG

GND

DTGL

GND

V

DD

(Digital)

REF RESET

Receive Section

Terminal Functions

TERMINAL

NAME NO.

I/O

DESCRIPTION

ANLG GND 17,18 Analog ground return for all internal analog circuits. Not internally connected to DGTL GND.
AUX IN+ 24 I Noninverting auxiliary analog input stage. AUX IN + can be switched into the bandpass filter and A/D

converter path via software control. If the appropriate bit in the control register is a 1, the auxiliary inputs

p

–

p

–

p

will re lace the IN+ and IN– in uts. If the bit is a 0, the IN+ and IN– in uts will be used (see the AIC DX

data word format section).
AUX IN– 23 I Inverting auxiliary analog input (see the above AUX IN+ description).
DGTL GND 9 Digital ground for all internal logic circuits. Not internally connected to ANLG GND.
DR 5 O Data receive. DR is used to transmit the ADC output bits from the AIC to the TMS320 (SMJ320) serial port.

This transmission of bits from the AIC to the TMS320 (SMJ320) serial port is synchronized with the SHIFT

CLK signal.
DX 12 I Data transmit. DX is used to receive the DAC input bits and timing and control information from the TMS320

(SMJ320). This serial transmission from the TMS320 (SMJ320) serial port to the AIC is synchronized with

the SHIFT CLK signal.
EODR 3 O End of data receive. (See the WORD/BYTE description and Serial Port Timing diagram.) During the

word-mode timing, EODR

is a low-going pulse that occurs immediately after the 16 bits of A/D information

have been transmitted from the AIC to the TMS320 (SMJ320) serial port. EODR

can be used to interrupt

a microprocessor upon completion of serial communications. Also, EODR

can be used to strobe and enable
external serial-to-parallel shift registers, latches, or external FIFO RAM, and to facilitate parallel data bus
communications between the AIC and the serial-to-parallel shift registers. During the byte-mode timing,
EODR

goes low after the first byte has been transmitted from the AIC to the TMS320 (SMJ320) serial port
and is kept low until the second byte has been transmitted. The DSP can use this low-going signal to
differentiate between the two bytes as to which is first and which is second. EODR

does not occur after

secondary communication.

TLC32044C, TLC32044E, TLC32044I, TLC32044M, TLC32045C, TLC32045I
VOICE-BAND ANALOG INTERFACE CIRCUITS

SLAS017F – MARCH 1988 – REVISED MA Y 1995

4

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

Terminal Functions (continued)

TERMINAL

NAME NO.

I/O

DESCRIPTION

EODX

11 O End of data transmit. (See the WORD/BYTE description and Serial Port Timing diagram.) During the

word-mode timing, EODX

is a low-going pulse that occurs immediately after the 16 bits of D/A converter
and control or register information have been transmitted from the TMS320 (SMJ320) serial port to the AIC.
EODX

can be used to interrupt a microprocessor upon the completion of serial communications. Also,

EODX

can be used to strobe and enable external serial-to-parallel shift registers, latches, or an external
FIFO RAM, and to facilitate parallel data-bus communications between the AIC and the serial-to-parallel
shift registers. During the byte-mode timing, EODX

goes low after the first byte has been transmitted from
the TMS320 (SMJ320) serial port to the AIC and is kept low until the second byte has been transmitted. The
DSP can use this low-going signal to differentiate between the two bytes as to which is first and which is
second.

FSR

4 O Frame sync receive. In the serial transmission modes, which are described in the WORD/BYTE description,

FSR

is held low during bit transmission. When FSR goes low, the TMS320 (SMJ320) serial port begins

receiving bits from the AIC via DR of the AIC. The most significant DR bit is present on DR before FSR

goes

low. (See Serial Port Timing and Internal Timing Configuration diagrams.) FSR

does not occur after

secondary communications.

FSX

14 O Frame sync transmit. When FSX goes low , the TMS320 (SMJ320) serial port begins transmitting bits to the

FSX

yg,()gg

AIC via DX of the AIC. In all serial transmission modes, which are described in the WORD/BYTE description,
FSX is held low during bit transmission (see Serial Port Timing and Internal Timing Configuration diagrams).

IN+ 26 I Noninverting input to analog input amplifier stage
IN– 25 I Inverting input to analog input amplifier stage
MSTR CLK 6 I Master clock. MSTR CLK is used to derive all the key logic signals of the AIC, such as the shift clock, the

switched-capacitor filter clocks, and the A/D and D/A timing signals. The Internal Timing Configuration
diagram shows how these key signals are derived. The frequencies of these key signals are synchronous
submultiples of the master clock frequency to eliminate unwanted aliasing when the sampled analog signals
are transferred between the switched-capacitor filters and the A/D and D/A converters (see the Internal
Timing Configuration diagram).

OUT+ 22 O Noninverting output of analog output power amplifier. OUT+ can drive transformer hybrids or

high-impedance loads directly in either a differential or a single-ended configuration.

OUT– 21 O Inverting output of analog output power amplifier. OUT– is functionally identical with and complementary

to OUT+.

REF 8 I/O Internal voltage reference. An internal reference voltage is brought out on REF. An external voltage

reference can also be applied to REF.

RESET 2 I Reset function. RESET is provided to initialize the T A, T A’, TB, RA, RA’, RB, and control registers. A reset

initiates serial communications between the AIC and DSP. A reset initializes all AIC registers including the
control register. After a negative-going pulse on RESET

, the AIC registers are initialized to provide an 8-khz
data conversion rate for a 5.184-MHz master clock input signal. The conversion rate adjust registers, TA’
and RA’, are reset to 1. The control register bits are reset as follows (see AIC DX data word format section):

d9 = 1, d7 = 1, d6 = 1, d5 = 1, d4 = 0, d3 = 0, d2 = 1.

This initialization allows normal serial-port communication to occur between the AIC and DSP.

SHIFT CLK 10 O Shift clock. SHIFT CLK is obtained by dividing the master clock signal frequency by four. SHIFT CLK is used

to clock the serial data transfers of the AIC, described in the WORD/BYTE

description below (see the Serial

Port Timing and Internal Timing Configuration diagrams).

V

DD

7 Digital supply voltage, 5 V ±5%

V

CC+

20 Positive analog supply voltage, 5 V ±5%

V

CC–

19 Negative analog supply voltage, –5 V ±5%

TLC32044C, TLC32044E, TLC32044I, TLC32044M, TLC32045C, TLC32045I

VOICE-BAND ANALOG INTERFACE CIRCUITS

SLAS017F – MARCH 1988 – REVISED MA Y 1995

5

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

Terminal Functions (continued)

TERMINAL

NAME NO.

I/O

DESCRIPTION

WORD/BYTE 13 I Used in conjunction with a bit in the control register, WORD/BYTE is used to establish one of four serial

modes. These four serial modes are described below.

AIC transmit and receive sections are operated asynchronously.

The following description applies when the AIC is configured to have asynchronous transmit and receive
sections. If the appropriate data bit in the control register is a 0 (see the AIC DX data word format section),
the transmit and receive sections are asynchronous.

L Serial port directly interfaces with the serial port of the DSP and communicates in two

8-bit bytes. The operation sequence is as follows (see Serial Port Timing diagrams).

1. FSX

or FSR is brought low.

2. One 8-bit byte is transmitted or one 8-bit byte is received.

3. EODX

or EODR is brought low.

4. FSX

or FSR emits a positive frame-sync pulse that is four shift clock cycles wide.

5. One 8-bit byte is transmitted or one 8-bit byte is received.

6. EODX

or EODR is brought high.

7. FSX

or FSR is brought high.

H Serial port directly interfaces with the serial ports of the TMS(SMJ)32020, TMS(SMJ)320C25, or

TMS(SMJ)320C30, and communicates in one 16-bit word. The operation sequence is as follows
(see Serial Port Timing diagrams):

1. FSX

or FSR is brought low.

2. One 16-bit word is transmitted or one 16-bit word is received.

3. FSX

or FSR is brought high.

4. EODX

or EODR emits a low-going pulse.

AIC transmit and receive sections are operated synchronously.

If the appropriate data bit in the control register is 1, the transmit and receive sections are configured to be
synchronous. In this case, the bandpass switched-capacitor filter and the A/D conversion timing are derived
from the TX counter A, TX counter B, and TA, T A ’, and TB registers, rather than the RX counter A, RX counter
B, and RA, RA’, and RB registers. In this case, the AIC FSX

and FSR timing are identical during primary

data communication; however, FSR

is not asserted during secondary data communication since there is
no new A/D conversion result. The synchronous operation sequences are as follows (see Serial Port Timing
diagrams).

L Serial port directly interfaces with the serial port of the DSP and communicates in two 8-bit

bytes. The operation sequence is as follows (see Serial Port Timing diagrams):

1. FSX

and FSR are brought low.

2. One 8-bit byte is transmitted and one 8-bit byte is received.

3. EODX

and EODR are brought low.

4. FSX

and FSR emit positive frame-sync pulses that are four shift clock cycles wide.

5. One 8-bit byte is transmitted and one 8-bit byte is received.

6. EODX

and EODR are brought high.

7. FSX

and FSR are brought high.

H Serial port directly interfaces with the serial port of the TMS(SJM)32020, TMS(SMJ)320C25, or

TMS320C30, and communicates in one 16-bit word. The operation sequence is as follows (see
Serial Port Timing diagrams):

1. FSX

and FSR are brought low.

2. One 16-bit word is transmitted and one 16-bit word is received.

3. FSX

and FSR are brought high.

4. EODX

or EODR emit low-going pulses.
Since the transmit and receive sections of the AIC are now synchronous, the AIC serial port with additional
NOR and AND gates interface to two SN74(54)299 serial-to-parallel shift registers. Interfacing the AIC to
the SN74(54)299 shift register allows the AIC to interface to an external FIFO RAM and facilitates parallel,
data bus communications between the AIC and the digital signal processor. The operation sequence is the
same as the above sequence (see Serial Port Timing diagrams).

TLC32044C, TLC32044E, TLC32044I, TLC32044M, TLC32045C, TLC32045I
VOICE-BAND ANALOG INTERFACE CIRCUITS

SLAS017F – MARCH 1988 – REVISED MA Y 1995

6

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

analog input

Two sets of analog inputs are provided. Normally , the IN+ and IN– input set is used; however, the auxiliary input
set, AUX IN + and AUX IN–, can be used if a second input is required. Each input set can be operated in either
differential or single-ended modes, since sufficient common-mode range and rejection are provided. The gain
for the IN +, IN–, AUX IN +, and AUX IN– inputs can be programmed to be either 1, 2, or 4 (see T able 2). Either
input circuit can be selected via software control. It is important to note that a wide dynamic range is assured
by the differential internal analog architecture and by the separate analog and digital voltage supplies and
grounds.

A/D bandpass filter, A/D bandpass filter clocking, and A/D conversion timing

The A/D high-pass filter can be selected or bypassed via software control. The frequency response of this filter
is presented in the following pages. This response results when the switched-capacitor filter clock frequency
is 288 kHz and the A/D sample rate is 8 kHz. Several possible options can be used to attain a 288-kHz
switched-capacitor filter clock. When the filter clock frequency is not 288 kHz, the low-pass filter transfer function
is frequency scaled by the ratio of the actual clock frequency to 288 kHz. The ripple bandwidth and 3-dB
low-frequency roll-off points of the high-pass section are 150 Hz and 100 Hz, respectively. However, the
high-pass section low-frequency roll-off is frequency scaled by the ratio of the A/D sample rate to 8 kHz.

The internal timing configuration and AIC DX data word format sections of this data sheet indicate the many
options for attaining a 288-kHz bandpass switched-capacitor filter clock. These sections indicate that the RX
counter A can be programmed to give a 288-kHz bandpass switched-capacitor filter clock for several master
clock input frequencies.

The A/D conversion rate is then attained by frequency dividing the 288-kHz bandpass switched-capacitor filter
clock with the RX counter B. Unwanted aliasing is prevented because the A/D conversion rate is an integral
submultiple of the bandpass switched-capacitor filter sampling rate, and the two rates are synchronously
locked.

A/D converter performance specifications

Fundamental performance specifications for the A/D converter circuitry are presented in the A/D converter
operating characteristics section of this data sheet. The realization of the A/D converter circuitry with
switched-capacitor techniques provides an inherent sample-and-hold.

analog output

The analog output circuitry is an analog output power amplifier. Both noninverting and inverting amplifier outputs
are brought out. This amplifier can drive transformer hybrids or low-impedance loads directly in either a
differential or single-ended configuration.

D/A low-pass filter, D/A low-pass filter clocking, and D/A conversion timing

The frequency response of this filter is presented in the following pages. This response results when the
low-pass switched-capacitor filter clock frequency is 288 kHz. Like the A/D filter, the transfer function of this filter
is frequency scaled when the clock frequency is not 288 kHz. A continuous-time filter is provided on the output
of the (sin x)/x correction filter to eliminate the periodic sample data signal information, which occurs at multiples
of the 288-kHz switched-capacitor filter clock. The continuous time filter also greatly attenuates any
switched-capacitor clock feedthrough.

TLC32044C, TLC32044E, TLC32044I, TLC32044M, TLC32045C, TLC32045I

VOICE-BAND ANALOG INTERFACE CIRCUITS

SLAS017F – MARCH 1988 – REVISED MA Y 1995

7

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

D/A low-pass filter, D/A low-pass filter clocking, and D/A conversion timing (continued)

The D/A conversion rate is attained by frequency dividing the 288-kHz switched-capacitor filter clock with TX
Counter B. Unwanted aliasing is prevented because the D/A conversion rate is an integral submultiple of the
switched-capacitor low-pass filter sampling rate, and the two rates are synchronously locked.

asynchronous versus synchronous operation

If the transmit section of the AIC (low-pass filter and DAC) and receive section (bandpass filter and ADC) are
operated asynchronously , the low-pass and bandpass filter clocks are independently generated from the master
clock signal. Also, the D/A and A/D conversion rates are independently determined. If the transmit and receive
sections are operated synchronously, the low-pass filter clock drives both low-pass and bandpass filters. In
synchronous operation, the A/D conversion timing is derived from, and is equal to, the D/A conversion timing
(see description of the WORD/BYTE

in the Terminal Functions table.)

D/A converter performance specifications

Fundamental performance specifications for the D/A converter circuitry are presented in the D/A converter
operating characteristics section of the data sheet. The D/A converter has a sample-and-hold that is realized
with a switched-capacitor ladder.

system frequency response correction

The (sin x) /x correction for the D/A converter zero-order sample-and-hold output can be provided by an
on-board second-order (sin x)/x correction filter. This (sin x)/x correction filter can be inserted into or deleted
from the signal path by digital signal processor control. When inserted, the (sin x)/x correction filter follows the
switched-capacitor low-pass filter. When the TB register (see Internal T iming Configuration section) equals 36,
the correction results of Figures 11 and 12 can be obtained.

The (sin x)/x correction can also be accomplished by deleting the on-board second-order correction filter and
performing the (sin x)/x correction in digital signal processor software. The system frequency response can be
corrected via DSP software to ±0.1-dB accuracy to a band edge of 3000 Hz for all sampling rates. This correction
is accomplished with a first-order digital correction filter, which requires only seven TMS320 (SMJ320)
instruction cycles. With a 200-ns instruction cycle, seven instructions represent an overhead factor of only 1.1%
and 1.3% for sampling rates of 8 and 9.6 kHz, respectively (see the (sin x)/x correction section for more details).

serial port

The serial port has four possible modes that are described in detail in the Terminal Functions table. These
modes are briefly described below and in the functional description for WORD/BYTE

.

• The transmit and receive sections are operated asynchronously, and the serial port interfaces directly

with the DSP.

• The transmit and receive sections are operated asynchronously, and the serial port interfaces directly

with the TMS(SMJ)32020, TMS(SMJ)320C25, and the TMS(SMJ)320C30.

• The transmit and receive sections are operated synchronously, and the serial port interfaces directly

with the DSP.

• The transmit and receive sections are operated synchronously, and the serial port interfaces directly

with the TMS(SMJ)32020, TMS(SMJ)320C25, TMS(SMJ)320C30, or two SN74(54)299 serial-to­parallel shift registers, which can then interface in parallel to the TMS(SMJ)32010, TMS(SMJ)320C15,
and SMJ320E15 to any other digital signal processor or to external FIFO circuitry.

TLC32044C, TLC32044E, TLC32044I, TLC32044M, TLC32045C, TLC32045I
VOICE-BAND ANALOG INTERFACE CIRCUITS

SLAS017F – MARCH 1988 – REVISED MA Y 1995

8

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

PRINCIPLES OF OPERATION

operation of TLC32044 or TLC32045 with internal voltage reference

The internal reference eliminates the need for an external voltage reference and provides overall circuit cost
reduction. Thus, the internal reference eases the design task and provides complete control over device
performance. The internal reference is brought out to a terminal and is available to the designer. To keep the
amount of noise on the reference signal to a minimum, an external capacitor can be connected between REF
and ANLG GND.

operation of TLC32044 or TLC32045 with external voltage reference

REF can be driven from an external reference circuit. This external circuit must be capable of supplying
250 µA and must be adequately protected from noise such as crosstalk from the analog input.

reset

A reset function is provided to initiate serial communications between the AIC and DSP and to allow fast,
cost-effective testing during manufacturing. The reset function initializes all AIC registers, including the control
register. After a negative-going pulse on RESET

, the AIC is initialized. This initialization allows normal serial port

communications activity to occur between AIC and DSP (see AIC DX data word format section).

loopback

This feature allows the user to test the circuit remotely . In loopback, OUT+ and OUT– are internally connected
to the IN+ and IN–. Thus, the DAC bits (d15 to d2), which are transmitted to DX, can be compared with the ADC
bits (d15 to d2), which are received from DR. An ideal comparison would be that the bits on DR equal the bits
on DX. However, there are some dif ference in these bits due to the ADC and DAC output offsets. The loopback
feature is implemented with digital signal processor control by transmitting the appropriate serial port bit to the
control register (see AIC DX data word format section).

TLC32044C, TLC32044E, TLC32044I, TLC32044M, TLC32045C, TLC32045I

VOICE-BAND ANALOG INTERFACE CIRCUITS

SLAS017F – MARCH 1988 – REVISED MA Y 1995

9

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

INTERNAL TIMING CONFIGURATION

XTAL

OSC

TMS(SMJ)320

DSP

Divide
by 135

Commercial

External

Front-End

Full-Duplex

Split-Band

Filters

†

TA Register

(5 bits)

TA’ Register

(6 bits)

(2’s compl)

Adder/

Subtractor

(6 bits)

Divide by 2

TB Register

(6 bits)

[TA = 9 (1)]
[TA = 18 (2)]
(6 bits)

TX Counter A

[TB = 40; 7.2 kHz]
[TB = 36; 8.0 kHz]
[TB = 30; 9.6 kHz]
[TB = 20; 14.4 kHz]
[TB = 15; 19.2 kHz]

TX Counter B

RA Register

(5 bits)

RA’ Register

(6 bits)

(2’s compl)

Adder/

Subtractor

(6 bits)

Divide by 2

RB Register

(6 bits)

[RA = 9 (1)]
[RA = 18 (2)]
(6 bits)

RX Counter A

[RB = 40; 7.2 kHz]
[RB = 36; 8.0 kHz]
[RB = 30; 9.6 kHz]
[RB = 20; 14.4 kHz]
[RB = 15; 19.2 kHz]

RX Counter B

Divide by 4

d0, d1 = 0,0
d0, d1 = 1,1

‡

d0, d1 = 0,1
d0, d1 = 1,0

‡

d0, d1 = 0,0
d0, d1 = 1,1

‡

d0, d1 = 0,1
d0, d1 = 1,0

‡

576-kHz
Pulses

576-kHz
Pulses

Low-Pass/
(sin x/x
Correction
Switched
Capacitor Filter
CLK = 288-kHz
Square Wave

D/A
Conversion
Frequency

A/D
Conversion
Frequency/
High-Pass
Switched
Capacitor
Filter CLK

Low-Pass
Switched
Capacitor Filter
CLK = 288-kHz
Square Wave

SHIFT CLK

1.296 MHz (1)

2.592 MHz (2)

MSTR CLK

5.184 MHz (1)

10.368 MHz (2)

20.736 MHz (1)

41.472 MHz (2)

Optional External Circuitry
for Full Duplex Modems

153.6-kHz
Clock (1)

†

Split-band filtering can alternatively be performed after the analog input function via software in the TMS(SMJ)320.

‡

These control bits are described in the AIC DX data word format section.

NOTE: Frequency 1 (20.736 MHz) is used to show how 153.6 kHz (for a commercially available modem split-band filter clock), popular speech

and modem sampling signal frequencies, and an internal 288-kHz switched-capacitor filter clock can be derived synchronously and as
submultiples of the crystal oscillator frequency . Since these derived frequencies are synchronous submultiples of the crystal frequency,
aliasing does not occur as the sampled analog signal passes between the analog converter and switched-capacitor filter stages.
Frequency 2 (41.472 MHz) is used to show that the AIC can work with high-frequency signals, which are used by high-speed digital signal
processors.

TLC32044C, TLC32044E, TLC32044I, TLC32044M, TLC32045C, TLC32045I
VOICE-BAND ANALOG INTERFACE CIRCUITS

SLAS017F – MARCH 1988 – REVISED MA Y 1995

10

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

explanation of internal timing configuration

All of the internal timing of the AIC is derived from the high-frequency clock signal that drives the master clock
input. The shift clock signal, which strobes the serial port data between the AIC and DSP, is derived by dividing
the master clock input signal frequency by four.

Low-pass:

SCF Clock Frequency (DńAorAńD path)

+

Master Clock Frequency

2 Contents of Counter A

Conversion Frequency

+

SCF Clock Frequency (DńAorAńD path)

Contents of Counter B

High-pass:

SCF Clock Frequency (AńD Path)+AńD Conversion Frequency

Shift Clock Frequency

+

Master Clock Frequency

4

TX counter A and TX counter B, which are driven by the master clock, determine the D/A conversion timing.
Similarly, RX counter A and RX counter B determine the A/D conversion timing. In order for the low-pass
switched-capacitor filter in the D/A path to meet its transfer function specifications, the frequency of its clock
input must be 288 kHz. If the clock frequency is not 288 kHz, the filter transfer function frequencies are
frequency-scaled by the ratios of the clock frequency to 288 kHz. Thus, to obtain the specified filter response,
the combination of master clock frequency and TX counter A and RX counter A values must yield a 288-kHz
switched-capacitor clock signal. This 288-kHz clock signal can then be divided by the TX counter B to establish
the D/A conversion timing.

The transfer function of the bandpass switched-capacitor filter in the A/D path is a composite of its high-pass
and low-pass section transfer functions. The high-frequency roll-off of the low-pass section meets the bandpass
filter transfer function specification when the low-pass section SCF is 288 kHz. Otherwise, the high-frequency
roll-off will be frequency-scaled by the ratio of the high-pass section’s SCF clock to 288 kHz. The low-frequency
roll-off of the high-pass section meets the bandpass filter transfer function specification when the A/D
conversion rate is 8 kHz. Otherwise, the low-frequency roll-off of the high-pass section is frequency-scaled by
the ratio of the A/D conversion rate to 8 kHz.

TX counter A and TX counter B are reloaded every D/A conversion period, while RX counter A and RX counter
B are reloaded every A/D conversion period. The TX counter B and RX counter B are loaded with the values
in the TB and RB registers, respectively . Via software control, the TX counter A can be loaded with either the
TA register, the TA register less the TA’ register, or the TA register plus the TA’ register. By selecting the TA
register less the TA’ register option, the upcoming conversion timing occurs earlier by an amount of time that
equals T A’ times the signal period of the master clock. By selecting the TA register plus the TA’ register option,
the upcoming conversion timing occurs later by an amount of time that equals T A ’ times the signal period of the
master clock. The D/A conversion timing can be advanced or retarded. An identical ability to alter the A/D
conversion timing is provided. In this case, however, the RX counter A can be programmed via software control
with the RA register, the RA register less the RA’ register, or the RA register plus the RA’ register.

The ability to advance or retard conversion timing is particularly useful for modem applications. This feature
allows controlled changes in the A/D and D/A conversion timing. This feature can be used to enhance
signal-to-noise performance, to perform frequency-tracking functions, and to generate nonstandard modem
frequencies.

TLC32044C, TLC32044E, TLC32044I, TLC32044M, TLC32045C, TLC32045I

VOICE-BAND ANALOG INTERFACE CIRCUITS

SLAS017F – MARCH 1988 – REVISED MA Y 1995

11

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

explanation of internal timing configuration (continued)

If the transmit and receive sections are configured to be synchronous (see WORD/BYTE description), then both
the low-pass and bandpass switched-capacitor filter clocks are derived from TX counter A. Also, both the D/A
and A/D conversion timing are derived from the TX counter A and TX counter B. When the transmit and receive
sections are configured to be synchronous, the RX counter A, RX counter B, RA register, RA’ register, and RB
registers are not used.

AIC DR or DX word bit pattern

d14 d13 d12 d11 d10 d9 d8 d7 d6 d5 d4 d3 d2 d1 d0d15

A/D or D/A MSB,
1st bit sent

1st bit sent of 2nd byte A/D or D/A LSB

AIC DX data word format section

d15 d14 d13 d12 d11 d10 d9 d8 d7 d6 d5 d4 d3 d2 d1 d0 Comments
primary DX serial communication protocol

←d15 (MSB) through d2 go to the D/A converter register → 0 0 The TX and RX counter As are loaded with the TA

and RA register values. The TX and RX counter Bs
are loaded with TB and RB register values.

←d15 (MSB) through d2 go to the D/A converter register → 0 1 The TX and RX counter As are loaded with the TA +

TA’ and RA + RA’ register values. The TX and RX
counter Bs are loaded with the TB and RB register
values. LSBs d1 = 0 and d0 =1 cause the next D/A
and A/D conversion periods to be changed by the
addition of T A ’ and RA ’ master clock cycles, in which
TA ’ and RA ’ can be positive or negative or zero (refer
to Table 1).

←d15 (MSB) through d2 go to the D/A converter register → 1 0 The TX and RX counter As are loaded with the T A –

TA’ and RA – RA’ register values. The TX and RX
counter Bs are loaded with the TB and RB register
values. LSBs d1 = 1 and d0 = 0 cause the next D/A
and A/D conversion periods to be changed by the
subtraction of TA’ and RA’ master clock cycles, in
which TA ’ and RA ’ can be positive or negative or zero
(refer to Table 1).

←d15 (MSB) through d2 go to the D/A converter register → 1 1 The TX and RX counter As are loaded with the TA

and RA register converter register values. The TX
and RX counter Bs are loaded with the TB and RB
register values. After a delay of four shift clock
cycles, a secondary transmission immediately
follows to program the AIC to operate in the desired
configuration.

NOTE: Setting the two least significant bits to 1 in the normal transmission of DAC information (primary communications) to the AIC initiates

secondary communications upon completion of the primary communications. Upon completion of the primary communication, FSX
remains high for four shift clock cycles and then goes low and initiates the secondary communication. The timing specifications for the
primary and secondary communications are identical. In this manner, the secondary communication, if initiated, is interleaved between
successive primary communications. This interleaving prevents the secondary communication from interfering with the primary
communications and DAC timing, thus preventing the AIC from skipping a DAC output. In the synchronous mode, FSR

is not asserted

during secondary communications.

TLC32044C, TLC32044E, TLC32044I, TLC32044M, TLC32045C, TLC32045I
VOICE-BAND ANALOG INTERFACE CIRCUITS

SLAS017F – MARCH 1988 – REVISED MA Y 1995

12

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

secondary DX serial communication protocol

x x | ← to TA register →| x x | ← to RA register → | 0 0 d13 and d6 are MSBs (unsigned binary)
x | ← to TA’ register →| x | ← to RA’ register → | 0 1 d14 and d7 are 2’s complement sign bits
x | ← to TB register → | x | ← to RB register → | 1 0 d14 and d7 are MSBs (unsigned binary)
x x x x x x d9 x d7 d6 d5 d4 d3 d2 1 1

Control
Register

d2 = 0/1 deletes/inserts the A/D high-pass filter
d3 = 0/1 disables/enables the loopback function
d4 = 0/1 disables/enables the AUX IN+ and AUX IN–
d5 = 0/1 asynchronous/synchronous transmit and receive sections
d6 = 0/1 gain control bits (see gain control section)
d7 = 0/1 gain control bits (see gain control section)
d9 = 0/1 delete/insert on-board second-order (sin x)/x correction filter

reset function

A reset function is provided to initiate serial communications between the AIC and DSP. The reset function
initializes all AIC registers, including the control register. After power has been applied to the AIC, a
negative-going pulse on RESET

initializes the AIC registers to provide an 8-kHz A/D and D/A conversion rate
for a 5.184 MHz master clock input signal. The AIC, except the control register, is initialized as follows (see AIC
DX data word format section):

REGISTER

INITIALIZED

REGISTER

VALUE (HEX)

TA 9
TA’ 1
TB 24
RA 9
RA’ 1
RB 24

The control register bits are reset as follows (see AIC DX data word format section):

d9 = 1, d7 = 1, d6 = 1, d5 = 1, d4 = 0, d3 = 0, d2 = 1

This initialization allows normal serial port communications to occur between AIC and DSP. If the transmit and
receive sections are configured to operate synchronously and the user wishes to program different conversion
rates, only the TA, TA’, and TB register need to be programmed, since both transmit and receive timing are
synchronously derived from these registers (see the terminal functions table and AIC DX word format sections).

The circuit shown in Figure 1 provides a reset on power up when power is applied in the sequence given under
power-up sequence. The circuit depends on the power supplies reaching their recommended values a minimum
of 800 ns before the capacitor charges to 0.8 V above DGTL GND.

V

CC+

V

CC–

RESET

200 kΩ

0.5 µF

TLC32044/TLC32045

5 V

–5 V

Figure 1. Power-Up Reset