TCM320AC36, TCM320AC37

VOICE-BAND AUDIO PROCESSORS (VBAP

™)

SLWS003C – MAY 1992 – REVISED APRIL – 1998

4

POST OFFICE BOX 655303

Terminal Functions

TERMINAL

NAME

NO.

I/O

DESCRIPTION

NAME

DW, N

PT

AGND

—

34

Ground return for all internal analog circuits

AVCC

—

4

5-V supply voltage for all internal analog circuits

CLK

11

19

I

Clock input. In the fixed-data-rate mode, CLK is the master clock input as well as the transmit and

receive data clock input . In the variable-data-rate mode, CLK is the master clock input only (digital).

DCLKR

7

14

I

Selection of fixed- or variable-data-rate operation. When DCLKR is connected to VCC, the device

operates in the fixed-data-rate mode. When DCLKR is not connected to VCC, the device operates in

the variable-data-rate mode, and DCLKR becomes the receive data clock (digital).

DGND

—

27

Ground return for all internal digital circuits

DIN

8

15

I

Receive data input. Input data is clocked in on consecutive negative transitions of the receive data

clock, which is CLK for a fixed data rate and DCLKR for a variable data rate (digital).

DOUT

13

21

O

Transmit data output. Transmit data is clocked out on consecutive positive transitions of the transmit

data clock, which is CLK for a fixed data rate and DCLKX for a variable data rate (digital).

DVCC

—

9

5-V supply voltage for all internal digital circuits

EARA

2

44

O

Earphone output. EARA forms a differential drive when used with the EARB signal (analog).

EARB

3

45

O

Earphone output. EARB forms a differential drive when used with the EARA signal (analog).

EARGS

4

46

I

Earphone gain set input of feedback signal for the earphone output. The ratio of an external potential

divider network connected across EARA and EARB adjusts the power amplifier gain. Maximum gain

occurs when EARGS is connected to EARB. Minimum gain occurs when EARGS is connected to

EARA. Earphone frequency response correction is performed using an RC approach (analog).

EARMUTE

10

17

I

Earphone output mute control signal. When EARMUTE is low, the output amplifier is disabled and no

audio is sent to the earphone (digital).

FSR

9

16

I

Frame-synchronization clock input for the receive channel. In the variable-data-rate mode, this signal

must remain high for the duration of the time slot. The receive channel enters the standby condition

when FSR is TTL-low for five frames or longer. The device enters a production test-mode condition

when either FSR or FSX is held high for five frames or longer (digital).

FSX

12

20

I

Frame synchronization clock input for the transmit channel. FSX operates independently of FSR, but

also in an analogous manner to FSR. The transmit channel enters the standby condition when FSX

is low for five frames or longer. The device enters a production test-mode condition when either FSX

or FSR is held high for five frames or longer (digital).

GND

16

—

Ground return for all internal circuits

LINSEL

15

26

I

Linear selection input. When low, LINSEL selects linear coding/decoding. When high, LINSEL selects

companded coding/decoding. Companding code on the ’AC36 is

µ-law, and companding code on the

’AC37 is A-law (digital).

MICBIAS

20

42

O

Microphone bias. MICBIAS voltage for the electret microphone is equal to VMID.

MICGS

19

41

O

Output of the internal microphone amplifier. MICGS is used as the feedback to set the microphone

amplifier gain. If sidetone is required, it is accomplished by connecting a series network between

MICGS and EARGS (analog).

MICIN

18

40

I

Microphone input. Electret microphone input to the internal microphone amplifier (analog)

MICMUTE

6

11

I

Microphone input mute control signal. When MICMUTE is active (low), zero code is transmitted (dig.).

PDN

1

43

I

Power-down input. When PDN is low, the device powers down to reduce power consumption (digital).

TSX/DCLKX

14

22

I/O

Transmit time slot strobe (active-low output) or data clock (input) for the transmit channel. In the

fixed-data-rate mode, TSX/DCLKX is an open-drain output that pulls to ground and is used as an

enable signal for a 3-state buffer. In the variable-data-rate mode, DCLKX becomes the transmit data

clock input (digital).

VCC

5

—

5-V supply voltage for all internal circuits

VMID

17

36

O

VCC /2 bias voltage reference. A pair of external, low-leakage, high-frequency capacitors (1 µF and

470 pF) should be connected between VMID and ground for filtering.