Datasheet TCA3388DP, TCA3388FP Datasheet (Motorola)

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Order this document by TCA3388/D

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The TCA3388 is a telephone line interface circuit which performs the basic
functions of a telephone set in combination with a microcontroller and a ringer.
It includes dc and ac line termination, the hybrid function with 2 adjustable
sidetone networks, handset connections and an efficient supply point.

FEATURES

Line Driver and Supply

• DC and AC Termination of the Telephone Line

• Selectable DC Mask: France, U.K., Low Voltage

• Current Protection

• Adjustable Set Impedance for Resistive and Complex Termination

• Efficient Supply Point for Peripherals

• Hook Status Detection

Handset Operation

• Transmit and Receive Amplifiers

• Double Anti–Sidetone Network

• Line Length AGC

• Microphone and Earpiece Mute

• Transmit Amplifier Soft Clipping

Dialing and Ringing

• Interrupter Driver for Pulse–Dialing

• Reduced Current Consumption During Pulse–Dialing

• DTMF Interfacing

• Ringing via External Ringer

TELEPHONE LINE

INTERFACE

SEMICONDUCTOR

TECHNICAL DATA

20

1

DP SUFFIX

PLASTIC PACKAGE

CASE 738

20

1

FP SUFFIX

PLASTIC PACKAGE

CASE 751D

PIN CONNECTIONS

Application Areas

• Corded Telephony

• Cordless Telephony Base Station

• Answering Machines

• Fax

• Intercom

• Modem

This document contains information on a new product. Specifications and information herein
are subject to change without notice.

MOTOROLA ANALOG IC DEVICE DATA

120

RXI

2

TXI

3

Mic

4

LAO

5

LAI

6

HYL

7

HYS

8

CM

9

IMP

SAO SAI

ORDERING INFORMATION

Device

TCA3388DP
TCA3388FP

 Motorola, Inc. 1995

Temperature Range

(Top View)

Tested Operating

TA = 0° to +70°C

19
18
17
16
15
14
13
12
1110

RXO2
RXO1
Gnd
V

CC

I

ref

MUT
PI
HSO

DCM

Package

DIP

SOIC

1

TCA3388

ÁÁÁ

ÁÁÁ

ÁÁÁ
ÁÁÁ

ÁÁÁ

ÁÁÁ

Simplified Block Diagram

DC and AC
Termination

Line +

Handset

Earpiece

Handset

MIcrophone

Ear

Mic

DC Mask Generation

AC Termination

2–4 Wire Conversion

Microcontroller

Interface

This device contains 1,911 active transistors.

MAXIMUM RATINGS

Rating Symbol Min Max Unit

Maximum Junction Temperature T
Storage Temperature Range T

NOTE: Devices should not be operated at or outside these values. The “Recommended Operating

Limits” provide for actual device operation.

J

stg

– +150 °C

–65 +150 °C

RECOMMENDED OPERATING CONDITIONS

Characteristic Symbol Min Typ Max Unit

Operating Temperature Range T

A

0 – +70 °C

Supply

Stabilizer

Line Driver

Line –

DC ELECTRICAL CHARACTERISTICS (T

Characteristic

= 25°C)

A

Symbol Min Typ Max Unit

VOLTAGE REGULATOR

Regulated Supply at Pin 17 V

CC

ICC = 7.0 mA 3.4 3.7 4.0
ICC = 20 mA 3.45 3.75 4.05

ICC = 80 mA 3.5 3.8 4.1

Current Consumption at Pin 17, Pin PI = High I

CC

– – 600 µA

DRIVER DC CHARACTERISTICS

Available Current at LAO

I4
Source Current 45 70 100
Sink Current –100 –70 –45

Amplifier A8 Driver Slope
LAO Voltage (PI = High, I4 = 100 µA)
Internal Offset (Pins 5 to 10)

S8

V

LAO

VO1–VO2

0.7

30

1.0

–

–

80

SPEECH AMPLIFIERS

IMP Voltage (Pin 9, Closed Loop)
Earpiece Amplifier DC Bias (R

= 100 kΩ)

ext

RXI, Pin 1 V
RXO1 Pin 19 V
RXO2, Pin 20 V
Offset (V

RXO1

– V

) V

RXO2

V

IMP

RXI
RXO1
RXO2
Offset

–

1.6

– 1.6 –
– 1.7 –
– 1.45 –
– 0.25 0.70

1.2
270
140

–

Vdc

µA

µA/mV

mV
mV

Vdc
Vdc

2

MOTOROLA ANALOG IC DEVICE DATA

TCA3388

ÁÁÁ

ÁÁÁ
ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

DC ELECTRICAL CHARACTERISTICS (continued) (T

= 25°C)

A

Characteristic UnitMaxTypMinSymbol

SPEECH AMPLIFIERS

HYL and HYS DC Bias Voltage

Normal Mode V
PI = High V

Microphone Amplifier DC Bias at TXI
Saturation Voltage at Mic @ 1.0 mA
Leakage Current into Mic @ 3.7 V

HY1
HY2

V

TXI

V

Mic

I

Leak

– 2.4 –
– 1.4 –

–
–
–

1.45
250

–

300

–

2.0

HOOK STATUS OUTPUT (Pin 13)

High Level Voltage @ – 5.0 µA Load Current, Off–Hook, V

SAI

= Max

V

HSOH

2.7

2.9

–

Maximum Load Current

Normal Mode I
PABX Mode I

Low Level Voltage @ + 5.0 µA Load Current, V

= – 5.0 mV

SAI

Normal On–Hook V
PI = High V

Time Delay from On–Hook or Off–Hook

HSOL

HSOH

HSOL

HSOLPI

T

Del

– – 5.0

20 – –

– – 0.60

2.7 2.9 –
–

3.5

–

PULSE INPUT (Pin 14)

Input Impedance
DC Bias Voltage

Z

PI

V

PIL

–
–

160

1.4

–
–

Input Current

Make Phase I
Break Phase I

PIL

PIH

–1.0 – 1.0

–10 – 10

MUTE INPUT (Pin 15)

Input Impedance
DC Bias Voltage

Z

MI

V

MI

–
–

160

1.4

–
–

Input Current

Speech Mode I
Mute Mode I

MIL

MIH

–1.0 – 1.0

–10 – 10

DC MASK CHARACTERISTICS

French

Internal Slope RI 120 160 200 mV/µA
Voltage on SAI (I2C = 3.6 µA) V
Voltage on SAI (I2D = 4.0 µA) V

C
D

Delta Offset Voltage on SAI (I2E = 30 µA) VE–V

D

0.40 0.47 – Vdc
– 0.49 0.57 Vdc
– – 30 mV

U.K.

Internal Slope RI 210 260 310 mV/µA
Voltage on SAI (I2C = 3.5 µA) V
Voltage on SAI (I2D = 3.9 µA) V

C
D

Delta Offset Voltage on SAI (I2E = 30 µA) VE–V

D

0.59 0.70 – Vdc
– 0.72 0.83 Vdc
– 20 50 mV

Low Voltage Mode

Internal Slope RI 100 125 150 mV/µA
Voltage on SAI (I2C = 13 µA) V
Voltage on SAI (I2D = 15 µA) V
Delta Offset Voltage on SAI (I2E = 20 µA) VE–V

Overvoltage Protection Threshold (V

LAI

– V

SAO

)

V

C
D

D

Clamp1

1.0 1.2 – Vdc
– 1.3 1.55 Vdc
– – 100 mV

French and U.K. DC Masks 530 580 650
Low Voltage DC Mask 280 – 385

Protection Voltage Level (V

LAI

– V

SAO

)

V

Clamp2

French and U.K. DC Masks 350 – 440
Low Voltage DC Mask 280 – 440

Vdc

Vdc

mV

µA

Vdc

µA

Vdc

ms

kΩ

Vdc

µA

kΩ

Vdc

µA

mV

mV

MOTOROLA ANALOG IC DEVICE DATA

3

TCA3388

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

ÁÁÁ

AC ELECTRICAL CHARACTERISTICS

Characteristic

(TA = 25°C)

Symbol Min Typ Max Unit

TRANSMIT MODE

French and U.K.

Maximum Transmit Gain (I2 = 3.0 µA) Kµ0 11.25 12.5 13.75
Line Length Regulation (I2 = 30 µA) ∆Kµ 5.5 6.5 7.5
Gain in Protection Mode (I2 = 30 µA) Kµp 10.5 12.5 14.5

Low Voltage Mode

Maximum Transmit Gain (I2 = 3.0 µA) Kµ0 11.25 12.5 13.75
Line Length Regulation (I2 = 8.2 µA) ∆Kµ 4.5 6.0 7.5
Gain in Protection Mode (I2 = 8.2 µA) Kµp 10.5 12.5 14.5

Gain Reduction when Microphone is Muted

∆Kµm

60

–

RECEIVE MODE

French

Maximum Internal Transconductance (I2 = 3.0 µA) G
Line Length Regulation (I2 = 18 µA) ∆G
Hybrid Weighting Factor (I2 = 18 µA) m
Line Length Regulation (HYS @ VCC, I2 = 9.0 µA) ∆G
Protection Mode (I2 = 18 µA) G

e0

e

r

e

ep

150 180 210 µA/V

2.95 3.7 4.45 dB

0.4 0.5 0.6

1.5 2.1 2.5 dB

145 185 230 µA/V

U.K.

Maximum Internal Transconductance (I2 = 3.0 µA) G
Line Length Regulation (I2 = 18 µA) ∆G
Hybrid Weighting Factor (I2 = 13 µA) m
Line Length Regulation (HYS @ VCC, I2 = 9.0 µA) ∆G
Protection Mode (I2 = 18 µA) G

e0

e

r

e

ep

150 180 210 µA/V

2.8 3.5 4.3 dB

0.4 0.5 0.6

1.4 1.9 2.4 dB

145 185 230 µA/V

Low Voltage Mode

Maximum Internal Transconductance (I2 = 3.0 µA) G
Line Length Regulation (I2 = 8.0 µA) ∆G
Hybrid Weighting Factor (I2 = 7.0 µA) m
Line Length Regulation (HYS @ VCC, I2 = 4.0 µA) ∆G
Protection Mode (I2 = 8.0 µA) G

Earpiece Gain Reduction when Muted

∆G

e0

e

r

e

ep

em

150 185 210 µA/V

4.2 5.7 7.2 dB
– 0.5 –
– 3.0 – dB

145 185 230 µA/V

60

–

TRANSMIT PABX MODE

French and U.K.

Transmit Gain (I2 = 3.0 µA) K
Variation with Line Length (I2 = 30 µA) ∆K

PABX

PABX

9.25 10.5 11.75

– 0.5 – 0.5

Low Voltage Mode

Transmit Gain (I2 = 3.0 µA) K
Variation with Line Length (I2 = 30 µA) ∆K

PABX

PABX

9.25 10.5 11.75

– 0.5 – 0.5

RECEIVE PABX MODE

French

Internal Transconductance (I2 = 5.0 µA) G
Hybrid Weighting Factor (I2 = 5.0 µA) m
Variation with Line Length (I2 = 30 µA) ∆G

U.K.

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Internal Transconductance (I2 = 5.0 µA) G
Hybrid Weighting Factor (I2 = 5.0 µA) m
Variation with Line Length (I2 = 30 µA) ∆G

Low Voltage Mode

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Internal Transconductance (I2 = 3.0 µA) G
Hybrid Weighting Factor (I2 = 3.0 µA) m
Variation with Line Length (I2 = 30 µA) ∆G

PABX

r

PABX

ÁÁÁ

PABX

r

PABX

ÁÁÁ

PABX

r

PABX

120 145 170 µA/V

0.8 0.9 1.0

– 0.5 – 0.5 dB

ÁÁ

120 145 170 µA/V

ÁÁ

0.65 0.75 0.85

– 0.5 – 0.5 dB

ÁÁ

120 145 170 µA/V

ÁÁ

– 0.9 –

– 0.5 – 0.5 dB

DISTORTION

French

Transmit (I2 = 10 µA) THDT – – 3.0
Receive (I2 = 6.0 µA) VE = 700 mV THDR – – 3.0

VE = 1250 mV – – 5.0

NOTE:VE is the differential earpiece voltage across Pins 19 and 20.

–

–

ÁÁ

ÁÁ

dB

dB

dB

dB

dB

dB

ÁÁ

ÁÁ

%

4

MOTOROLA ANALOG IC DEVICE DATA

TCA3388

ÁÁÁ

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

AC ELECTRICAL CHARACTERISTICS (continued) (T

= 25°C)

A

Characteristic UnitMaxTypMinSymbol

DISTORTION

Low Voltage

Transmit (I2 = 10 µA) THDT – – 3.0
Receive (I2 = 6.0 µA) VE = 700 mV THDR – – 3.0

VE = 1250 mV – – 5.0

NOTE:VE is the differential earpiece voltage across Pins 19 and 20.

TYPICAL TEMPERATURE PERFORMANCE

Characteristic Typical Value @ 25°C Typical Change – 20 to + 60°C

VCC Regulated Supply @ Pin 17
Current Consumption at Pin 17, Pin PI = High
Amplifier A8 Driver Slope
Voltage on SAI V

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C

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V

D

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Internal Slope for Low Voltage Mode
Transmit Gain Kµ0
Line Length Regulation ∆Kµ French

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Internal Transconductance G
Line Length Regulation ∆G

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e0

e

French

NOTE: Temperature data is typical performance only, based on sample characterization, and does not provide guaranteed limits over temperature.

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U.K.

L.V .

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U.K.

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L.V .

3.7

400 µA

1.0 µA/mV

French = 0.47 Vdc

U.K. = 0.70 Vdc

French = 0.49 Vdc

U.K. = 0.72 Vdc

125 mV/µA

12.5 dB

6.5 dB

6.5 dB

6.0 dB

180 µA/V

3.7 dB

3.5 dB

5.7 dB

– 0.8 mV/°C

– 0.55 µA/°C

– 0.0035 µA/mV/°C

БББББББББ

БББББББББ

0.35 mV/°C

0.07 mV/µA/°C

0.01 dB/°C

< 0.3 dB Variation

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< 0.3 dB Variation

– 0.05 dB/°C
< 1.0 dB Variation
< 0.5 dB Variation

< 0.5 dB Variation

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– 0.04 dB/°C

%

PIN FUNCTION DESCRIPTION

Pin Symbol Description

1 RXI Earphone Amplifier Input
2 TXI Microphone Amplifier Input
3 Mic Microphone Bias Current Sink
4 LAO Line Driver Amplifier Output
5 LAI Line Driver Amplifier Input
6 HYL Hybrid Network Input for Long Lines
7 HYS Hybrid Network Input for Short Lines
8 CM DC Mask Signal Filtering

9 IMP Reference Voltage
10 SAO Line Current Sense Amplifier Output
11 SAI Line Current Sense Amplifier Input
12 DCM DC Mask Select
13 HSO Hook Status Output, PABX Mode Select
14 PI Pulse Input
15 MUT Mute Input
16 I
17 V

ref
CC

18 Gnd Ground
19 RXO1 Earphone Amplifier Output
20 RXO2 Earphone Amplifier Inverted Output

Reference Current
Supply Voltage

MOTOROLA ANALOG IC DEVICE DATA

5

TCA3388

DESCRIPTION OF THE CIRCUIT

Concept

With a TCA3388, a microcontroller and a ringer, a basic
telephone set can be built according to the concept depicted
in Figure 1.

In off–hook position, the application is in speech mode.
The line current flows through transistor T2 and supplies the
externals (microcontroller) at the supply point VCC which is
stabilized by the TCA3388. The V
adjusted by the external components Z0, Z1, Z21 and R1
which are in a regulator loop, acting on transistor T2. The ac

, I

line

characteristic is

line

Figure 1. T elephone Concept with TCA3388

impedance is generated in a similar way . The handset can be
connected directly to the TCA3388. Via a logic level interface,
the microcontroller drives the TCA3388 to perform the
DTMF/pulse–dialing. The user keyboard has to be connected
to the microcontroller. In on–hook position, a ringing melody
can be generated with a ringer application.

The block diagram of the TCA3388, in Figure 2, shows the
basic blocks of the device plus the essential external
components.

A/B

Line +

C20

Line –

Hookswitch

R6

R9

Z0Z1

Z21

Ringer

Handset

R1

Figure 2. Block Diagram of the TCA3388 with Essential Components

Z0

Z21

C5

RXO1

19

RXO2

20

RXI

TXI

Mic

Mute, AGC

1

2

3

Ear

Mute, AGC

Mic

TCA3388

Z2

C17
R19

7 8 10 5 9 16

HYS CM SAO LAI IMP I

DC Mask Generation

2–4 Wire Conversion

SAI

11

Z

DCM

R1

Z1

R20

6

HYL

AC Termination

Line Length AGC

Protection

Micro–Interface

DCM MUTPIHSO

12

13 14 15

R22

C16

Hook–Detect

PABX

To/From

Microcontroller

DTMF

T2

V

CC

Gnd

Supply–

Stabilizer

References

Line
Driver

R12

ref

MicroTCA3388

V

CC

17

Gnd
18

LAO
4

T2

C7

T3

6

MOTOROLA ANALOG IC DEVICE DATA

TCA3388

DC CHARACTERISTICS AND ST ARTUP

The dc mask has the general form as depicted in Figure 3.

The TCA3388 offers the possibility to adjust the dc
characteristics of all 4 regions via mask selection and
hardware adjustments.

The selection of the 3 masks, France, United Kingdom
and Low Voltage, can be done via the Z

network at Pin

DCM

DCM as shown in Figure 4. For French and U.K. masks, the
region 3 with the high slope is within the normal dc feeding
conditions. For Low Voltage mask the region 3 will be outside
this and the dc mask is mainly determined by regions 1
and 2.

Figure 3. General Form of the DC Mask

of the TCA3388

V

Line

4

V

LP

3

V

LK

V

LC

2

1

Figure 4. Selection of the Country Mask via Pin DCM

I

µ

( A)

DCM

FR

14
11

LV

4

0

0.5 2.0 2.5 3.0 3.2

Z

L.V . FRU.K.

for the L.V., U.K. and FR Mask

DCM

CC

R23
56 k

R24
47 k

U.K.

C21
10

V

(V)

DCM

DCMDCMVDCM

µ

R25

1.0 M

C18
470 n

0

I

LC

Region 1: Startup, Low Line Current, High Slope
Region 2: Mid–Range Line Current, Low Slope
Region 3: High Line Current, High Slope
Region 4: Overload Protection

I

LP

Figure 5. DC Part of the Block Diagram of the TCA3388

Line +

C16

Z2

Line –

Z1

HYL

HYS

2

I

I2S

L

CM

G

G

CM

I

LKIVLP

IMP

RX

SAI

1.6 V

I

Line

2 V

BE

VO1

The capacitor in the U.K. network is to ensure a stable
selection of the mask during all working modes and
transitions. The capacitor in the French network is used to
create a startup in Low Voltage Mask.

The adjustment possibilities will be discussed below with
the aid of the block diagram of Figure 5.

T2

Z21

SAO

TCA3388

Z0

LAI

LAO

Gnd

VO2

R1

T3

R5

C7

V

CC

MOTOROLA ANALOG IC DEVICE DATA

7

TCA3388

The TCA3388 offers the possibility to connect 2 sidetone
networks Z1 and Z2. For correct dc operation, the dc
impedance of these networks must be equal. When only 1
sidetone network is used, Pin HYS has to be connected to
HYL. All formulas below are based on a single sidetone
network, so only Z1 appears. When 2 sidetone networks are
used, Z1 has to be replaced by Z1//Z2.

In region 1, the transfer of the amplifier G at the HYL/HYS
inputs equals zero. The voltage difference between SAO and
SAI will equal VO1. The slope RE1 of the V
characteristic will equal:

Z0

RE1+

In region 2, the output current of the amplifier G will be
proportional to the input current. As a result the voltage
between SAO and SAI will increase with the line voltage.
Speech signals on the line are of no influence on this
because they are filtered out via capacitor C16. The slope
RE2 of the V

, I

Line

RE2+

Line

R1 x

ǒ

R1 x

1

characteristic will equal:

ȡ

1

)

ȧ
Ȣ

In region 3, the output current of the amplifier G is kept
constant. As a result the slope in region 3 will equal the slope
of region 1.

The transfer from region 2 to 3 occurs at the point VLK, I
defined by:

)

RI

Z1

Z21

1

)

Ǔ

Z21

Z0

ȣ
ȧ
Ȥ

Line

, I

Line

LK

When the line voltage becomes lower than VLP, the
overload condition is removed and the TCA3388 will leave
region 4.

The current drawn from the line by the dc part is used to
supply the TCA3388 and peripheral circuits. The excess loop
current is absorbed by the voltage regulator at Pin VCC,
where a filter capacitor is connected. The reference for the
circuit is Pin Gnd.

Startup of the application is ensured by an internal startup
circuit. When the line current flows, the hook status output
pin HSO goes high. This informs the microcontroller that the
set is off–hook. When the line current is no longer present the
pin will go low again. Because the line current is monitored,
and not the line voltage, also an interrupt of the exchange
can be recognized.

AC CHARACTERISTICS

Impedance

In Figure 6, the block diagram of the TCA3388 performing
the ac impedance is depicted. As can be seen it is partly
common with the dc mask block diagram. The part
generating the dc mask is replaced by a dc voltage source
because for ac, this part has no influence.

Figure 6. AC Stage of the TCA3388

Line +

Z0

T2

R5

VLK = Z1 x I2CD + 2 VBE + VCD + VO2

Z21

xǒZ1 x I2CD)2V

Z0

ILK+

I2CD

With:
and 2 VBE  1.4 V, V02  1.1 V

When the French or U.K. mask is selected, this transfer
takes places for line currents of 30 mA to 40 mA depending
on the components settings. With the Startup and Low
Voltage mask, the transfer lies outside the normal operating
range with line currents of 90 mA or more. In most
applications the transfer from region 1 to 2 takes place for line
currents below 10 mA.

With proper settings, region 4 is entered only during an
overload condition. In this mode, the power consumption in
the telephone set is limited. In order to detect an overload
condition, the voltage between the Pins LAI and SAO is
monitored. When the voltage difference is larger than the
threshold V
for the line voltage VLP at this point is given as:

VLP+

When the protection mode is entered, the line current is
reduced to a lower value ILP of:

ILP+

I2C)I2D

+

Clamp1

Z0

Z21

V

2

, the protection is made active. The relation

xV

Clamp2

R1

,andVCD+

Clamp1

)(VO1 – VO2

)

R1

BE

VCD)

)

Ǔ

)

VC)

V

VO2

2

CD

V

D

,

V

TCA3388

LAI

Z21

SAO

V02

VO1

SAI

Line –

When calculating the ac loop, it can be derived that the set

impedance Zin equals

V

Zin+

As can be noticed, the formula for the ac impedance Z
equals the formula for the dc slope in regions 1 and 3.
However, because for the dc slope the resistive part of Z0
and Z21 are used, the actual values for Zin and the dc slopes
do not have to be equal.

A complex impedance can be made by making either Z0
or Z21 complex. When Z0 is made complex to fit the set
impedance the transmit characteristics will be complex as
well. The complex impedance is therefore preferably made
via the Z21 network. Because Z21 is in the denominator of
the Zin formula, Z21 will not be a direct copy of the required
impedance but a derivative of it. Figure 7 gives this derived
network to be used for Z21.

Line

I

Line

+

R1ǒ1

R1

)

LAO

Gnd

Z0

Z21

T3

Ǔ

[

R1 x

CC

C7

Z0

Z21

in

8

MOTOROLA ANALOG IC DEVICE DATA

TCA3388

Figure 7. Derived Network for Z21 in Case of

Complex Set Impedance

Gnd

Ǔ

R

v

R

w

C

w

Ǔ

Ǔ

R

R1xZ0

Rb–R1

ǒ

Ra)

b

2

xC

v

Rb–R1

b

SAO LAI

R

a

R

b

C

b

Rv+

Rw+

ǒ

2

Ra)

R1xZ0ǒRa–R1

4R

4R

Cw+

b

R1 x Z0

TRANSMIT

When a current is injected on Pin LAI, via the loop
depicted in Figure 6, a signal is created on the line. In this
way the microphone signals and DTMF signals (from an
external source) are transmitted. It can be derived that the
signal voltage on the line (V
current injected in LAI (I

V

Line

+

LAI

–I

LAI

With this relation, a simplified replacement circuit can be
made for the transmit amplifier (see Figure 8). Here the
product of I

and Z0 is replaced by one voltage source.

LAI

Figure 8. Replacement Diagram for

the Transmit Amplifier

–I

*Z0

LAI

) depends on the signal

Line

) according to:

Z0 x Z

V

Line

Line

Z

Line

Z

Line

Z

in

x

Zin)

The microphone signal current is derived from the

microphone signal according to the schematic in Figure 9.

Figure 9. Microphone Amplifier Input Stage

Ku

TCA3388

Line AGC

Mute

I

LAI

R

C

Mic

Handset

Microphone

Mic

V

CC

C

u

R

u

TXI

Mic

I

u

R

TXI

The input stage of Figure 9 consists of a current amplifier

with transfer Ku, an input impedance of 1.0 k (R

TXI)

, plus an
attenuator which reduces the signal current at high line
currents (AGC). This attenuator can be switched on/off via
the microcontroller. The input current Iu within the telephony
speech band is derived from the microphone signal according

V

Iu+

R

Mic

)

u

Ru)

R

TXI

With: Vu = signal of the microphone only loaded with R

[

V

u

R

u

Mic

The overall gain from microphone to line (ATX) now follows

as

ATX+

V

Line

V

u

+

Ku
R

Z0 x Z

x

Zin)

u

Line

Z

Line

Practically, the gain can be varied only with Z0, Ru and

R

.

Mic

The TCA3388 offers the possibility to mute the
microphone, also called privacy mode, by making the MUT
Pin high. During pulse–dialing, the microphone bias is
switched off. Pin Mic will be made high impedance, shutting
off the microphone dc current. This reduces the current
consumption of the circuit during pulse–dialing.

MOTOROLA ANALOG IC DEVICE DATA

9

Line +

TCA3388

Figure 10. Receive Part of the TCA3388

R20Z1

C17

R19Z2

+ V01

BE

HYL

G

G

e

e

Line Mute
AGC

R1

IMP

HYS

2V

SAI Gnd

Line –

RECEIVE

The receive part of the TCA3388 is shown in Figure 10.

The receive signal is picked up by the amplifiers at the
HYL/HYS inputs. These are the same amplifiers present in
the dc loop of Figure 5. The signal is first converted to current
by the transconductance amplifier with transfer Ge. The
multiplier placed after performs the line length AGC. It
switches over between the 2 signals at HYS and HYL
according to the line current via a modulation factor m.
Afterwards, the current is converted back to voltage via the
external feedback network Z
available at output RXO1, and inverted at RXO2.

From the diagram of Figure 10 the receive gain (ARX) can
be derived as:

V

ARX+

RXO

V

Line

+

Ge x R1 x Z

. The resulting voltage is

Load

1

ǒ

x

Load

Z

H

)

1

Ǔ

Z

in

1.6 V

V

ref

TCA3388

RXO1

RXI

R

Load

–1X

C

Load

RXO2

C

ear

Handset
Earpiece

SIDETONE

When a transmit signal is transmitted to the line, a part of
the signal is returned to the receive channel due to the
architecture of the 2 to 4 wire conversion of the hybrid. During
transmit, the signal on the line will be –I
receive, the signal on the line will be I
replacing Zin in the formula for the receive gain, it follows that
the signal on the earpiece output due to a sending signal on
the line will be:

V

ear

V

Line (transmit)

In applications with 1 sidetone network where HYS is
connected to HYL, it follows:

+

GexR1xZ

H

+

R1 x Z1

R20

1

Z

Load

+

Z

Line

1

HL

Line

ǒ

x

x Z

Line

x Zin. When

1

–

Z

H

. During

1

Ǔ

Z

Line

H

H

+

R1 x Z1

+

mx

R20

R1 x Z1

in case of 1 sidetone network and

R20

)

(m –1)

R19

R1 x Z2

in case of

1

With:

Z

HYS connected to HYL, or

1

Z

2 sidetone networks

More information on ZH and the modulation factor m can

be found under the sidetone characteristics.

The earpiece can either be connected as a single ended or
as a differential load. The above calculated gain is valid for the
single ended case. When connecting as a differential load, the
gain is increased by 6.0 dB. The TCA3388 offers the
possibility to mute the signal coming from the line to the
earpiece. This can be useful during pulse– and DTMF–dialing.

10

ZH has to be chosen according the average line
impedance, and the average linelength of the countries
involved in the application. A complex sidetone network can
be made via a complex Z1 which is preferred above making
R20 complex. The coupling capacitor C17 in series with R20
is meant only to block dc.

For applications with 2 sidetone networks it follows:

1

Z

H

The ZH thus exists as ZHL for long lines with low line
currents and as ZHS for short lines with high line currents.
This can be useful in applications such as DECT and
handsfree where the sidetone has to be minimized to reduce
the effect of delayed echoing and howling respectively. The
TCA3388 will automatically switch over between the 2 hybrid
networks as a function of line current. This is expressed in the

R20

+

m

R1 x Z1

m

MOTOROLA ANALOG IC DEVICE DATA

)

(m –1)

1

)

Z

(m – 1)

HL

R19

R1 x Z2

1

Z

HS

+

TCA3388

factor m. The relation between the line current and the factor
m is depicted in Figure 1 1.

Figure 11. Modulation Factor m as a Function

of Line Current

m

1.0

0.5

I

III0

For low line currents below I

LstopLmLstart

, thus long lines, the

Lstart

Line

factor m equals 1. This means the hybrid network ZHL is fully
used. For high line currents above I

, thus short lines, the

Lstop

factor m equals 0. This means the hybrid network ZHS is fully
used. Both networks are used 50% for the intermediate line
current Ilm.

The switch over between the 2 networks takes place in
region 3 for the French and U.K. mask and in region 2 for the
Low Voltage mask.

LINE LENGTH AGC

The TCA3388 offers the possibility to vary the transmit and
receive gain over line length in order to compensate for the
loss in gain at longer line lengths. In the block diagrams of the
transmit and receive channels (Figures 9, 10) the line AGC is
drawn. The line AGC can be switched off by connecting a
150 kΩ resistor between HSO and Gnd. In this case, the
transmit and receive gain are lowered by 2.0 dB with respect
to the value calculated in the formulas above.

The line AGC characteristics for both transmit and receive
channel have the general shape depicted in Figure 12.

Figure 12. General Line AGC Characteristics

Gain

Gain

Nominal

Gain

Reduced

Gain

I

Lstart

I

Lrange

For low line currents, and thus long lines, the gains are
nominal. When the line current has increased above I

Nominal Gain

+

1

)

IL–I

I

Lrange

Lstart

I

Line

Lstart

with a current I

, the gain is reduced by 6.0 dB. Due to

Lrange

the general characteristics of the line AGC curve, the gain will
be decreased further for higher currents.

For France and U.K., the line AGC will be active in region

3 of the dc characteristics. The I

is approximately equal

Lstart

to the ILK. The range is calculated from:

I

Lrange

Z1 x(I2R – I2CD

+

R

E3

)

For Low Voltage mask, the line AGC is active in region 2.

DIALING

Pulse–dialing is performed by making pin PI high. As a
result the output LAO goes low and the loop will be
disconnected. Internally the current consumption of the
circuit is reduced and the current through the microphone is
switched off.

DTMF–dialing is performed by supplying a DTMF signal
current to Pin LAI. This is the same node where the
microphone signal currents are internally applied. Therefore,
for the DTMF gain the same formulas apply. Because the
microphone preamplifier is bypassed, there is no influence
on DTMF signals by the line length AGC.

A DTMF confidence tone can be generated on the
earpiece by injecting a signal current at the RXI pin. Because
only the earpiece amplifier itself is used, there are no effects
from AGC or hybrid switchover.

For correct DTMF–dialing the pin MUT has to be made
high. This mutes both the microphone and earphone
preamplifier. In this way signals from the microphone will not
be amplified to the line and signals from the line are not
amplified to the earpiece.

The complete interfacing of the DTMF generator with the
TCA3388 is shown in the typical application.

SUPPORT MATERIAL

Device Specification: Brief description of the TCA3388,

block diagram, device data, test
diagram, typical application

User manual TCA3388:Extended description of the circuit

and its concept, adjustment
procedure, application hints and
proposals

Demonstration board: Shows performance of the TCA3388

in its basic application

TYPICAL APPLICATION

The typical application below is based on the demoboard
of the TCA3388. It contains the speech transmission part,
diode bridge, hook switch and microcontroller interfacing.
The dc mask setting on the bottom left is given for France,
U.K. and Low Voltage applications. The component values
are given in the table of Figure 14. The line driver is extended
with T1, D5 and R3 which increases the signal swing under
low line voltage conditions.

MOTOROLA ANALOG IC DEVICE DATA

11

TCA3388

Rp

T2

Line +

Ring

A/B

On–Hook

D1 D2

R3

R5

Z1

C1

Off–Hook

T1

D5

D4D3

T3

B/A

C2

R1

Line–

Line Driver

Mic

V

R7

C6

R9

Mic +

Mic –

Ear +

Ear –

R6

R27

Gnd

C3

Receive GainPABX

C20

Figure 13. T ypical Application

C13

R14

C10

C11

R15

R18

C12

R28 R21

R13

C23

Z1

R16

R17

Z2

Z0

Z21

Long Line

Short Line

C16

R29

C14

R20

C15

R19

C24

C25

C17

C5

1

20

TCA3387

TCA3388

TCA3389

10

11

C8R11

C4

R8

Gain

Sidetone Balance

DTMF

Transmit Gain

R26

FR LV UK

R23

C7

C22

C19

C26

R12

R22

R24

C21

C18

R25

Mask Setting

12

DTMF

HSO

Pulse

Mute

V

CC

Gnd

MOTOROLA ANALOG IC DEVICE DATA

TCA3388

Item

R

Figure 14. List of Components for T ypical Application TCA3388

Location

on Board

R1 Line Driver 16 16 18
R3 Line Driver 10 k
R5 Line Driver 1.0 k
R6 Receive Gain 150 k
R7 Transmit Gain 2.2 k
R8 DTMF Gain 470 k

R9 Transmit Gain 39 k
R11 DTMF Gain 56 k
R12 I
R13 Z0 580 k 560 k 330 k
R14 Z0 – 680 k 620 k
R15 Z1 620 k 1.2 m 1.8 m
R16 Z1 130 k 300 k 330 k
R17 Z2 – 620 k 820 k
R18 Z2 – 820 k 1.5 m
R19 Sidetone Bal – 18 k 39 k
R20 Sidetone Bal 7.5 k 15 k 22 k
R21 Z21 16 k 16 k 18 k
R22 PABX 150 k
R23 Mask Setting – – 56 k
R24 Mask Setting – – 47 k
R25 Mask Setting – 1.0 m –
R26 Pin 19 10 Stability
R27 Pin 20 10 Stability
R28 Z21 0
R29 Transmit Gain 1.0 k V

Rp Line+ 0 22 22

C1 A/B 10 n EMC

C2 Line Driver 470 p

C3 Receive Gain 220 p

C4 DTMF Gain 10 n

C5 Transmit Gain 10 n

C6 Transmit Gain 6.8 n

C7 Pin 17 220 µ VCC, 10 V

C8 DTMF Gain 10 n
C10 Z0 – 4.7 n 330 p
C11 Z1 220 p 120 p 150 p
C12 Z2 – 82 p 150 p
C13 Z21 470 p
C14 Sidetone Bal 470 p Stability
C15 Sidetone Bal – 470 p 470 p Stability
C16 Pin 8 680 n 680 n 2.2 µ DC Mask
C17 Sidetone Bal 680 n

, Pin 16 121 k 1.0%

ref

Basic L.V . France U.K.

Application

Mic

emarks

MOTOROLA ANALOG IC DEVICE DATA

13

TCA3388

Figure 14. List of Components for T ypical Application TCA3388

Location

Item

Item

C18 Mask Setting – 470 n –
C19 Pin 19 100 n Stability
C20 Pin 20 100 n Stability
C21 Mask Setting – – 10 µ 10 V
C22 Pin 17 100 n Close to Pin
C23 Z21 –
C24 Transmit Gain 10 µ V
C25 Pin 2 4.7 n EMC
C26 Pin 16 1.0 n EMC

T1 Line Driver MPSA92 PNP–HV

T2 Line Driver MJE350 PNP–HV

T3 Line Driver MPSA42 NPN–HV

D1–D4 Bridge 4 x 1N4004 HV

D5 Line Driver 1N4004 Signal

Z1 A/B MKP1V270 Sidac

Location

on Board

on Board

Application

U.K.FranceBasic L.V .

, 10 V

Mic

Remarks

Remarks

14

MOTOROLA ANALOG IC DEVICE DATA

TCA3388

OUTLINE DIMENSIONS

DP SUFFIX

PLASTIC PACKAGE

CASE 738-03

ISSUE E

-T-

SEATING
PLANE

-A-

1120

B

110

C

K

E

N

GF

D

20 PL

0.25 (0.010) T A

M M

PLASTIC PACKAGE

CASE 751D–03

–A–

20

11

–B–

P10X

0.010 (0.25)

1

10

D20X

S

M

0.010 (0.25) B

A

T

S

C

SEATING

–T–

18X

G

K

PLANE

FP SUFFIX

ISSUE E

M

M

B

J

F

L

J 20 PL

0.25 (0.010) T B

M

M

M M

R

X 45

NOTES:

1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.

2. CONTROLLING DIMENSION: INCH.

3. DIMENSION L TO CENTER OF LEAD WHEN
FORMED PARALLEL.

4. DIMENSION B DOES NOT INCLUDE MOLD
FLASH.

INCHES MILLIMETERS

MIN MINMAX MAX

DIM

A
B
C
D
E

F
G
J
K
L
M
N

NOTES:

1. DIMENSIONING AND TOLERANCING PER
ANSI Y14.5M, 1982.

2. CONTROLLING DIMENSION: MILLIMETER.

3. DIMENSIONS A AND B DO NOT INCLUDE
MOLD PROTRUSION.

4. MAXIMUM MOLD PROTRUSION 0.150
(0.006) PER SIDE.

5. DIMENSION D DOES NOT INCLUDE
DAMBAR PROTRUSION. ALLOWABLE
DAMBAR PROTRUSION SHALL BE 0.13
(0.005) TOTAL IN EXCESS OF D DIMENSION
AT MAXIMUM MATERIAL CONDITION.

DIM MIN MAX MIN MAX

A 12.65 12.95 0.499 0.510
B 7.40 7.60 0.292 0.299
C 2.35 2.65 0.093 0.104
D 0.35 0.49 0.014 0.019
F 0.50 0.90 0.020 0.035
G 1.27 BSC 0.050 BSC

_

J 0.25 0.32 0.010 0.012
K 0.10 0.25 0.004 0.009
M 0 7 0 7
P 10.05 10.55 0.395 0.415
R 0.25 0.75 0.010 0.029

1.070

1.010

0.260

0.240

0.180

0.150

0.022

0.015

0.050 BSC

0.070

0.050

0.100 BSC

0.015

0.008

0.140

0.110

0.300 BSC

°

15

0

0.040

0.020

__

25.66

6.10

3.81

0.39

1.27

0.21

2.80

°

0.51

27.17

6.60

4.57

0.55

1.27 BSC

1.77

2.54 BSC

0.38

3.55

7.62 BSC

°

°

0

15

1.01

INCHESMILLIMETERS

__

MOTOROLA ANALOG IC DEVICE DATA

15

TCA3388

Motorola reserves the right to make changes without further notice to any products herein. Motorola makes no warranty , representation or guarantee regarding
the suitability of its products for any particular purpose, nor does Motorola assume any liability arising out of the application or use of any product or circuit,
and specifically disclaims any and all liability, including without limitation consequential or incidental damages. “T ypical” parameters can and do vary in different
applications. All operating parameters, including “T ypicals” must be validated for each customer application by customer’s technical experts. Motorola does
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unintended or unauthorized application, Buyer shall indemnify and hold Motorola and its officers, employees, subsidiaries, affiliates, and distributors harmless
against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death
associated with such unintended or unauthorized use, even if such claim alleges that Motorola was negligent regarding the design or manufacture of the part.
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INTERNET: http://Design–NET.com 51 Ting Kok R oad, Tai Po, N.T., Hong Kong. 852–26629298

16

◊

MOTOROLA ANALOG IC DEVICE DATA

TCA3388/D

*TCA3388/D*