TSC TS34118 Technical data

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TS34118

SOP-28 DIP-28

Voice Switched Speakerphone Circuit

Supply Voltage Range -1.0 V to 7.0V

IVB Current 500µA

Microphone Amplifier, & Hybrid Amplifier Gain 40 dB

General Description

The TS34118 Voice Switched Speakerphone Circuit incorporates the necessary amplifiers, attenuators, level detectors,

and control algorithm to form the heart of a high quality hands-free speakerphone system. Included are a microphone

amplifier with adjustable gain and MUTE control, Transmit and Receive attenuators which operate in a complementary

manner, level detectors at both input and output of both attenuators, and background noise monitors for both the transmit

and receive channels. A Dial Tone Detector prevents the dial being attenuated by the Receive background noise monitor

circuit. Also included are two line drive amplifiers which can be used to form a hybrid network in conjunction with an

external coupling transformer. A high-pass filter can be used to filter out 60Hz noise in the receive channel, or for other

filtering functions .A Chip Disable pin permits powering down the entire circuit to conserve power on long loops where

loop current is at a minimum.

The TS34118 may be operated from a power supply, or it can be powered from the telephone line, requiring typically

5.0mA. The TS34118 can be interfaced directly to Tip and Ring (through a coupling transformer) for stand-alone

operation, or it can be used in conjunction with a handset speech network and/or other features of a feature phone

Features

 Improved attenuator gain range: 52dB between

transmit and receive.

 Low voltage operation for line-powered applications

(3.0-6.5V).

 4-point signal sensing for improved sensitivity.  Back ground noise monitors for both transmit

and receive paths.

 Standard 28-pin plastic DIP package and SOP

package available.

 Microphone amplifier gain set by external

resistors-mute function included.

 Chip disable for active/standby operation.  On board filter pinned-out for user defined function.  Dial tone detector to inhibit receive idle mode during

dial tone presence.

 Compatible with TS34119 speaker amplifier.

Ordering Information

Part No. Operating Temp. Package

TS34118CD DIP-28

-20 ~ +70

TS34118CS

SOP-28

Absolute Maximum Rating

Description Value Unit

Supply voltage (pin 4) -1.0, +7.0

Voltage at CD (pin 3), MUT (pin 12) -1.0,Vcc +1.0

Voltage at VLC (pin 13) -1.0,Vcc +0.5

Voltage at TXI (pin 9),RXI (pin 21),FI(pin 2) -0.5,Vcc +0.5

Storage temperature range -65 to +150

TS34118 1-20 2004/09 rev. B

Recommended Operating Conditions

Description

Min. Typ. Max. Units

Supply voltage (pin 4) (see Text) 3.5 -- 6.5 V CD input (pin 3), MUT input (pin 12) 0 -- Vcc V IVB current (pin 15) - -- 500 µA VLC (pin 13) 0.3xVB -- VB V Attenuator input signal voltage (pin 9,21) 0 -- 350 mVrms Microphone amplifier, Hybrid amplifier gain 0 -- 40 dB Load current @RXO, TXO (pins 8,22)

@MCO (pin 10)

@HTO-, HTO+ (pin 6,5)

0 0 0

±2.0 ±1.0 ±5.0

Ambient operating temperature range -20 -- +60 ℃

Electrical Characteristics (T

=+25, Vcc=5.0V, CD≤ 0.8V, unless noted)

Parameter Symbol Min Typ Max Unit

Power Supply

Vcc supply current (Vcc=6.5V, CD=0.8V) (Vcc=6.5V, CD=2.0V) CD input resistance (Vcc=VCD=6.5V) CD input voltage - High

- Low VB output voltage (Vcc=3.5V) (Vcc=5.0V) VB output resistance (IVB=1.0mA) R VB power supply rejection ratio (CVB=220µF,f=1.0KHz)

PSRR -- 54 -- dB

Icc

CDH

CDL

-- 400 -- Ω

OVB

2.0 0

1.8

5.5

600

1.3

2.1

8.0

800

Vcc

0.8

2.4

µA

KΩ

V V

Attenuators (T

=+25℃)

Receive attenuator gain (f=1.0KHz, VLC=VB ) Rx model, RXI=150mVrms (Vcc=5.0V) Rx model, RXI=150mVrms (Vcc=3.5V) Gain change –Vcc=3.5V versus Vcc=5.0V AGC gain change –Vcc=2.8V versus Vcc=5.0V* Idle model, RXI=150mVrms

Range (Rx to Tx model)

∆G ∆G

∆G

Volume control range (Rx model, 0.3VB<VLC<VB)

RXO DC voltage (Rx model)

∆RXO DC voltage (Rx to Tx model)

RXO high voltage (Iout=-1.0mA RXI=VB+1.5V)

RXO low voltage (Iout=+1.0mA, RXI=VB-1.0, Output measured with respect to V

RXI input resistance (RXI<350mVrms)

∆V

Transmit attenuator gain (f=1.0KHz)

Tx model , TXI=150mVrms Idle model, TXI=150mVrms Range (Tx to Rx model)

∆G TXO DC voltage (Tx model) V ∆TXO DC voltage (Tx to Rx model) ∆V TXO High voltage (Iout=-1.0mA TXI=VB+1.5V) V TXO Low voltage (Iout=+1.0mA TXI=VB-1.0V, Output measured with respect to VB)*

RX1

RX2

RX1

RX3

27 35 -- dB

-- VB -- V

RXO

-- ±10 ±150 mV

RXO

3.7 -- -- V

RXOH

-- -1.5 -1.0 V

RXOL

7.0 10 14 KΩ

RXI

TXI

-- VB -- V

TXO

-- ±30 ±150 mV

TXO

3.7 -- -- V

TXOH

-- -1.5 -1.0 V

TXOL

+4.0 +4.0

-0.5

-22 49

+4.0

-22 49

+6.0 +6.0

-25

-20 52

+6.0

-20 52

+8.0 +8.0 +0.5

-15

-17 54

+8.0

-17 54

TS34118 2-20 2004/09 rev. B

Electrical Characteristics (T

Parameter Symbol Min Typ Max Unit

Attenuators-continued (TA=+25℃)

TXI input resistance (TXI<350mVrms) R

Gain tracking (G

Attenuator Control (T

CT voltage (pin 14-VB) Rx model (VLC=VB)

CT source current(switching to Rx mode) I

CT sink current(switching to Tx mode) I

CT slow idle current I

CT fast idle internal resistance RFI 1.5 2.0 3.6 KΩ

Microphone Amplifier (T

Output offset (V

Open loop gain (f<100Hz) A

Gain bandwidth GBWM -- 1.0 -- MHz Output High voltage (Iout=-1.0mA, Vcc=5.0V) V Output Low voltage (Iout=+1.0mA) V Input bias current (@MCI) IBM -- -40 -- nA Muting (∆Gain) (f=1.0KHz, V (300Hz<f<10KHz) MUT input resistance (Vcc=V MUT Input-High V MUT Input-Low V

Hybrid Amplifiers (TA=+25 )℃

HTO-offset(V HTO- to HTO+ offset (Feedback R=51KΩ) HB Open loop gain(HTI to HTO-, f<100Hz) A Gain bandwidth GBWH -- 1.0 -- MHz Closed loop gain(HTO- to HTO+) A Input bias current(@HTI) IBH -- -30 -- nA HTO- High voltage (Iout=-5.0mA) V HTO- Low voltage (Iout=+5.0mA) V HTO+ High voltage (Iout=-5.0mA) V HTO+ Low voltage (Iout=+5.0mA) V Distortion(300Hz<f<10KHz, see Figure 1) THDH -- 0.3 -- %

Level Detectors and Background Noise Monitors (T

Transmit-Receive switch threshold (Ratio of current at RLI1 + RLI2 to 20µA

at TLI1 + TLI2 to switch from Tx to Rx) Source current at RLO1, RLO2, TLO1, TLO2 I Sink current at RLO1, RLO2, TLO1, TLO2 I CPR, CPT output resistance (Iout=1.5mA) RCP -- 35 -- Ω CPR, CPT leakage current I

Filter (TA=+25℃)

Voltage offset at FO (VFO-VB, 220KΩ from VB to FI) FO FO sink current IFO 150 260 400 µA

FI bias current IFI -- -50 -- nA

+ GTX, @ Tx, Idle, Rx)* GTR -- ±0.1 -- dB

=+25℃)

Idle model Tx model

=+25℃,V

, feedback R=180KΩ) MCOvos -50 0 +50 mV

MCO-VB

=2.0V)

MUT

, Feedback R=51KΩ) H

HTO- -VB

=+25, Vcc=5.0V, CD≤ 0.8V, unless noted)

MUT

≤0.8V,A

=31dB unless otherwise noted)

VCL

=6.5V) R

=+25℃)

7.0 10 14 KΩ

TXI

-85 -60 -40 µA

CTR

+40 +60 +85 µA

CTT

-- 0 -- µA

CTS

70 80 -- dB

VOLM

3.7 -- -- V

MCOH

-- -- 200 mV

MCOL

GMT

50 90 -- KΩ

MUT

2.0 -- Vcc V

MUTH

0 -- 0.8 V

MUTL

-20 0 +20 mV

VOS

-30 0 +30 mV

VOS

60 80 -- dB

VOLH

-0.35 0 +0.35 dB

VCLH

3.7 -- -- V

HT-H

-- -- 250 mV

HT-L

3.7 -- -- V

HT+H

-- -- 450 mV

HT+L

0.8 1.0 1.2

-- -2.0 -- mA

LSO

-- 4.0 -- µA

LSK

-- -0.2 -- µA

CPLK

-200 -90 0 mV

VOS

-55

+240

-240

-68

TS34118 3-20 2004/09 rev. B

Electrical Characteristics (T

Parameter Symbol Min Typ Max Unit

System Distortion (TA=+25℃, f=1.0KHz)

Rx mode (from FI to RXO, FO connected to RXI)

Tx mode (from MCI to HTO-/HTO+, includes

Tx attenuator)

1. All currents into a device pin are positive, those out of a pin are negative. Algebraic convention rather than magnitude is used to define limits.

=+25, Vcc=5.0V, CD≤ 0.8V, unless noted)

THDR -- 0.5 3.0 %

THD

-- 0.8 3.0 %

Simplified Block Diagram

Temperature Characteristics

Parameter Typical Value @25℃ Typical Change –20 to +60℃

Vcc supply current (CD=0.8V) 5.0mA -0.3%/℃

Vcc supply current (CD=2.0V) 400µA -0.4%/℃

VB output voltage (Vcc=5.0V) 2.1V +0.8%/℃

Attenuator gain (Max Gain) +6.0dB 0.0008dB/℃

Attenuator gain (Max attenuation) -46dB 0.004dB/℃

Attenuator input resistance (@ TXI, RXI) 10KΩ +0.6%/℃

Dial tone detector threshold 15mV +20µV/℃

CT source, sink current ±60µA -0.15%/℃

Microphone, Hybrid amplifier offset 0 mV ±4.0µV/℃

Transmit-Receive switching threshold 1.0 ±0.02%/℃

Sink current at RLO1, RLO2, TLO1, TLO2 4.0µA -10nA/℃

Closed loop gain (HTO- to HTO+) 0 dB 0.001%/℃

TS34118 4-20 2004/09 rev. B

Pin Function Description

Pin Name Description

1 FO Filter output. Output impedance is less than 50 ohms.

2 FI Filter input. Input impedance is greater than 1.0Mohm.

3 CD

4 Vcc

5 HTO+

6 HTO- Output of the first hybrid amplifier. The gain of the amp is set by external resistors.

7 HTI Input and summing node for the first hybrid amplifier . DC level is≈VB.

8 TXO Output of the transmit attenuator. DC level is approximately VB.

9 TXI Input to the transmit attenuator. Max. Signal level is 350m Vrms . Input impedance is 10KΩ.

10 MCO Output of the microphone amplifier. The gain of the amplifier is set by external resistors.

11 MCI Input and summing node of the microphone amplifier. DC level is≈ VB.

12 MUT

13 VLC

14 CT An RC at this pin sets the response time for the circuit to switch modes.

15 VB

16 CPT An RC at this pin sets the time constant for the transmit background monitor.

17 TLI2 Input to the transmit level detector on the mike/speaker side.

18 TLO2

19 RLO2 Output of the receive level detector on the mike/speaker side.

20 RLI2 Input to the receive level detector on the mike/speaker side.

21 RXI

22 RXO Output of the receive attenuator. DC level is approximately VB.

23 TLI1 Input to the transmit level detector on the line side.

24 TLO1 Output of the transmit level detector on the line side.

25 RLO1

26 RLI1 Input to the receive level detector on the line side.

27 CPR An RC at this pin sets the time constant for the receive background monitor.

28 GND Ground pin for the entire IC.

Chip Disable. A logic low(<0.8V) sets normal operation. A logic high (>2.0V) disables the IC to

conserve power. Input impedance is norminally 90KΩ.

A supply voltage of +2.8 to +6.5 volts is required, at ≈5.0mA. As Vcc falls from 3.5 to 2.8volts,

an AGC circuit reduces the receive attenuator gain by ≈25dB (when in the receive mode).

Output of the second hybrid amplifier. The gain is internally set at –1.0 to provide a differential

output, in conjunction with HTO-, to the hybrid transformer.

Mute input. A logic low(<0.8V) sets normal operation. A logic high (>2.0V) mutes the

microphone amplifier without affecting the rest of the circuit. Input impedance is norminally

90KΩ.

Volume control input. When VLC=V

receive mode. When VLC=0.3V

mode.

An output voltage≈Vcc/2. This voltage is a system ac ground, and biases the volume control. A

filter cap is required

Output of the transmit level detector on the mike/speaker side, and input to the transmit

background monitor.

Input to the receive attenuator and dial tone detector. Max input level is 350mV RMS. Input

impedance is ≈10KΩ.

Output of the receive level detector on the line side, and input to the receive background

monitor.

, the receive attenuator is at maximum gain when in the

, the receive gain is down 35dB. Does not affect the transmit

TS34118 5-20 2004/09 rev. B

Typical Application Circuit

Figure 1. Hybrid Amplifier Distortion Test

Figure 2. TS34118 Block Diagram

TS34118 6-20 2004/09 rev. B

Introduction

The fundamental difference between the operation of a speakerphone and a handset is that of half-duplex versus full

duplex. The handset is full duplex since con-version can occur in both directions (transmit and receive) simultaneously.

A speakerphone has higher gain levels in both paths and attempting to converse full duplex results in oscillatory

problems due to the loop that exists within the system. The loop is formed by the receive and transmit paths, the hybrid,

and the acoustic coupling (speaker to microphone). The only practical and economical solution used to data is to design

the speakerphone to function in a half duplex mode – i.e. only one person speaks at a time, while the other listens. To

achieve this required a circuit which can detect who is talking, switch on the appropriate path (transmit or receive) and

switch off (attenuate) the other path. In this way, the loop gain is maintained less than unity. When the talkers exchange

function, the circuit must quickly detect this, and switch the circuit appropriately. By providing speech level detectors the

circuit operates in a “hands free” mode, eliminating the need for a “push to talk” switch.

The handset by the way, has the same loop as the speakerphone. But since the gains are considerably lower, and

since the acoustic compiling from the earpiece to the mouthpiece is almost non existent (the receiver is normally held

against a person’s eat.) oscillations don’t occur.

The TS341118 provides the necessary level detectors, attenuators, and switching control for a properly operating

speakerphone. The detection sensitivity and timing are externally controllable. Additionally, the TS34118 provides

background nodule monitor’s which make the circuit insensitive to room and line noise, hybrid amplifier, and other

associated functions, please refer to the Block Diagram (Figure 2) when reading the following sections.

Attenuators

The transmit and receive attenuators are complementary in function. i .e. when one is at maximum gain (+6.0dB), the

other is at maximum attenuation (-4.5dB), and vice verse. They sum of their gains remains constant (within a nominal

error hand of ±0.1dB) at a typical value of ~40dB (see Figure 10). Their purpose is to control the transmit and receive

paths to provide the half-duplex operation required in a speakerphone.

The attenuators are non-inverting, and have a –3.0dB (from max gain) frequency of 100KHz. The input impedance of

each attenuator (TXI and RXI) is nominally 10KΩ (see Figure 3), and the input signal should be limited to 350mVrms

(990mVp-p) to prevent distortion. That maximum recommended input signal is independent of the volume control

setting. The diode clamp on the inputs the input swing, and therefore the maximum negative output swing. This is the

reason for V

impedance is 10Ω until the output current limit typically 2.5mA) is reached.

RXOL

and VT

specification being defined as they are in the Electrical Characteristics. The output

XOL

Figure 3. Attenuator Input Stage

TS34118 7-20 2004/09 rev. B

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