Overview

The LA8638V provides dynamic range expansion, noise
suppression for enhancing the quality of audio signals in
cordless telephones and other communications systems.
This single chip provides the functions that make it ideal
for cordless telephones: a compressor with a logarithmic
compression ratio of 1/2, expander with a logarithmic
expansion ratio of 2, splatter filter, microphone amplifier,
BTL amplifier, waveform shaper for the receiving signal,
muting for both receiving and transmitting signals, and
standby operation.

Functions

· Transmitter circuits: compressor, microphone amplifier,

limiter (IDC), muting, output level changes to user-
specified levels, and splatter filter

· Receiver circuits: expander, buffer amplifier for filters,

muting, output level changes to user-specified levels,
and BTL amplifier

· Other circuits: waveform shaper for the receiving signal

and standby operation

Features

· Full processing of baseband signals for both receiving

and transmitting signals

· Built-in BTL receiver amplifier for driving a ceramic

speaker with a load of 2 k

· Standby operation that conserves battery power during

intermittent reception by disabling all but the waveform
shaper for the receiving signal

· Built-in splatter filter with user-specified fc
· Low-voltage operation (1.8 V to 5.5 V)

Package Dimensions

unit: mm

3191-SSOP30

Monolithic Linear IC

40398RM (OT) No. 5776-1/16

SANYO: SSOP30

[LA8638V]

SANYO Electric Co.,Ltd. Semiconductor Bussiness Headquarters

TOKYO OFFICE Tokyo Bldg., 1-10, 1 Chome, Ueno, Taito-ku, TOKYO, 110-8534 JAPAN

Low-voltage Compander IC

for Cordless Telephones

LA8638V

Ordering number : EN5776

Parameter

Symbol

Conditions

Ratings

Unit

Maximum power supply voltage

max

7.0

Maximum power dissipation

Pd max

75°C

100

Operating temperature

Topr

20 to +75

°C

Storage temperature

Tstg

40 to +125

°C

Specifications

Maximum Ratings

at Ta = 25°C

Parameter

Symbol

Conditions

Ratings

Unit

Recommended power supply voltage

2.4

Operating power supply voltage range

1.8 to 5.5

Operating Conditions

at Ta = 25°C

No. 5776-2/16

LA8638V

Parameter

Symbol

Conditions

Ratings

Unit

min

typ

max

Current drain with no signal

CCO

No signal

3.0

5.4

7.6

Standby current

STBY

Standby mode, No signal

0.4

0.7

0.95

[Transmitter block] V

inrefc

= 60 dBV = 0 dB, microphone amplifier gain = 40 dB, R

= 15 k

Output level

= Vinrefc = 0 dB

18.1

16.1

14.1

dBV

Gain change level

= 10 dB

3.5

4.0

4.4

Gain error

= 40 dB

2.0

0.7

+1.0

Total harmonic distortion

THDc

= 0 dB

0.45

1.0

Output noise voltage

Rg = 620

, f = 20 to 20 kHz

1.8

4.5

mVrms

Limiting voltage

= +30 dB, 1 kHz BPF

0.88

1.05

1.23

Vp-p

Microphone amplifier maximum voltage gain

VG max

Low pass filter attenuation

Lalt

= 5 kHz; fifth-order Butterworth function

12.0

16.5

25.0

filter (fc = 3.35 kHz)

Muting attenuation

ATTc

= +30 dB, 1 kHz BPF

dBV

Crosstalk level

CTc

RX--V

= 10 dBV, 1 kHz BPF

dBV

[Receiver block] V

inrefe

= 20 dBV = 0 dB, R

= 15 k

Output level

= V

inrefe

= 0 dB

18.8

16.3

13.8

dBV

Gain change level

= 0 dB

6.0

7.1

8.4

Gain error

= 30 dB

1.5

+0.3

+2.0

Output noise voltage

Rg = 620

, f = 20 to 20 kHz

100

µVrms

Muting attenuation

ATTe

= +10 dB, 1 kHz BPF

100

dBV

Crosstalk level

CTe

TX--V

= 40 dBV, 1 kHz BPF

dBV

[BTL amplifier] R

= 2 k

Maximum output voltage

btl

THD = 3%

3.2

4.2

Vp-p

Total harmonic distortion

THDbtl

= 5 dBV

0.4

1.0

[Data shaper] V

= 20 dBV, R

= 100 k

Duty factor

DUTY

Dead zone

UNSN

39.0

34.5

30.0

dBV

Output "H" level

2.2

2.38

Output "L" level

0.12

0.3

[Digital input characteristics]

Input "H" level 1

Pins 17, 18, 20, and 22

0.6 V

Input "L" level 1

Pins 17, 18, 20, and 22

0.25 V

Input "H" level 2

Pin 19

1.3

Input "L" level 2

Pin 19

0.3

Electrical Characteristics

at Ta = 25°C, V

= 2.4 V, f

= 1 kHz

Usage Notes

1. Internal Reference Voltages

The chip uses the following reference voltages internally.

Pin 29 (V

REF

) Power supply voltage follower (approximately 0.5 V

)

Pin 4 (V

REF

2) Fixed voltage (approximately 1.25 V)

2. Microphone Amplifier

Do not use the microphone amplifier as a buffer amplifier (non-reversing, zero-gain amplifier) because it is designed
for high-gain operation--that is, gains above 6 dB--and is susceptible to oscillation below that level.
For proper circuit balance, use the same resistance value for the bias resistor (between pins 28 and 29) and the
feedback resistor (between pins 26 and 27).

3. BTL Amplifier

The built-in BTL amplifier is designed for ceramic speakers only. Do not use it to drive a dynamic speaker.

4. Receiver Input Filter

The receiver input filter uses external capacitors and resistors to determine the cutoff frequencies. The external circuit
constants may be easily derived from the standardized circuit constants. Start by making all resistors the same size
and determine the capacitances required to achieve the desired cutoff frequencies from the circuit constants in Table
1. Then, because capacitors are not available for such precise values, choose the closest ones available and then fine-
tune the resistances. (As a result, the final resistances will not necessarily be equal.)
Once the filter constants have been established, choose the bias voltage supply resistor R

so that the total DC

resistance between pins 4 and 5 is on the order of 120 k

to standardize the voltage drop across this path due to the

small base current from the transistor in the pin 5 input circuit and thus the duty factor for the data shaper at the next
stage.

5. Splatter Filter Cutoff Frequency

The resistance between pin 24 and ground determines the cutoff frequency for the splatter filter in the transmitter
circuit. (See Graph 1 on p. 8.) To fine-tune this frequency, use two resistors and adjust them to achieve the desired
frequency.

6. Gain Change Levels

The resistance between pins 29 and 30 determines the gain change level for the transmitter circuits. (See Graph 2
on p. 8.)
The resistance between pin 9 and ground determines the gain change level for the receiver circuits. (See Graph 3
on p. 8.)

No. 5776-6/16

LA8638V

Table 1. Standardized Circuit Constants

The Bessel functions for cutoff frequencies do not incorporate the notion of 3-
dB attenuation. The 3-dB attenuation frequency for the second-order function
is 1.38 fc; for the third-order function, 1.75 fc.

Lowpass filter type

Second-order Butterworth function

0.7071

1.4142

Third-order Butterworth function

0.2025

3.5468

1.3926

Second-order Bessel function

0.5000

0.6667

Third-order Bessel function

0.1451

0.8136

0.5647

7. Protective Diodes Preventing Static Breakdown

The control pins and data output pins have had their upper protective diodes removed so as to permit direct
connection to a microcomputer.

No protective diodes:

(pin 15), GND (pins 1 and 12)

Lower protective diodes only:

Pins 16 to 20, 22

Both upper and lower protective diodes: All other pins

8. Preemphasis and Deemphasis

This chip provides preemphasis in the microphone amplifier and deemphasis in the BTL amplifier's input stage. The
amount depends on the CR time constants for the filters on the corresponding pins--the primary high pass filter on
the microphone amplifier's positive (pin 28) or negative (pin 27) input for preemphasis and the primary low pass filter
between pins 10 and 11 for deemphasis.

9. Full-Wave Rectifier Smoothing Capacitors

The external capacitors on pins 8 and 25 are for the full-wave rectifiers for the expander and compressor. They not
only smooth the output but also determine the time constant for the transient characteristics. This time constant is the
product of the capacitance and 15 k

, the input resistance of the full-wave rectifier. Although there is a tendency to

lower the time constant for the expander to reduce noise at the ends of words, the designer must keep in mind that
such cuts reduce the amount of smoothing and thus raise the risk of distortion.

10. Compressor's Summing Amplifier

Achieving a DC gain of 1 and an AC gain of infinity from the compressor's summing amplifier requires suppressing
AC feedback with the capacitor on pin 3. The cutoff frequency is determined by the product of its capacitance and the
internal resistance of 22.5 k

11. Standby Function

The chip's standby function does not produce a total shutdown of all circuits. It disables the audio signal processing
block, but leaves the waveform shaper block for the receiving signal operating. For this reason, it is not possible to
connect the battery directly to the power supply pin (pin 15). There must be an intervening transistor switch for an
intermittent power supply.

12. Control Modes

No. 5776-7/16

LA8638V

Pin 17

Pin 18

SUB-CNT1

SUB-CNT2

Mode

OPEN/HIGH

Standby

OPEN/HIGH

LOW

Receiver muted

LOW

OPEN/HIGH

Normal receiver output levels

LOW

Low receiver output levels

Pin Number

Pin Name

OPEN/HIGH

LOW

Pin 19

BTL-CNT

BTL amplifier disabled

BTL amplifier enabled

Pin 20

TX-MUTE

Transmitter muted

Transmitter enabled

Pin 22

TX-LVL-CNT

Normal transmitter output levels

High transmitter output levels

Note: The standby mode overrides all other mode settings.

Pin Number

Pin Name

Pin Voltage

Equivalent Circuit

Description

No. 5776-9/16

LA8638V

Pin Descriptions

GND

Ground for all circuits except BTL amplifier

1/2 V

Resistance voltage divider pin

REF

Reference voltage for all circuits except
receiver block

CMP-NF

AC feedback control for compressor's
summing amplifier DC gain: 1 AC gain:
Infinite

DT-V

REF

1.25 V

Reference voltage for receiver block This
supplies the bias voltage for pin 5.

RX-IN

1.25 V power

supply

Filter buffer input

RX-FIL-OUT

1.25 V

Filter buffer output

EXP-IN

Expander input. Voltage-current converter
input. Full-wave rectifier input.

EXP-RCT

Indeterminate

(when there is

no signal)

Full-wave rectifier output for expander block
(AC smoothing)

RX-ATT-ADJ

0.03 V

Pin for setting attenuation for receiver output
level switching

RX-OUT

Receiver block output

Continued on next page.

No. 5776-10/16

LA8638V

Continued from preceding page.

Pin Number

Pin Name

Pin Voltage

Equivalent Circuit

Description

BTL-GND

Ground for BTL amplifier

BTL-IN

BTL amplifier input

BTL-OUT1

BTL amplifier reversed output

BTL-OUT2

BTL amplifier non-reversed output

Power supply pin

FSK-OUT

Indeterminate

(when there is

no signal)

Comparator output (open collector output)

SUB-CNT1

Internal operating mode control pins. All four
have identical structures.

SUB-CNT2

TX-MUTE

TX-LVL-CNT

BTL-CNT

+ 0.65

----------

BTL amplifier operation control pins

TX-DATA-IN

/1.6

Transmitter data input

TX-OUT

/1.6

Transmitter output

FREQ-ADJ

0.01 V

Pin for setting cutoff frequency of splatter
filter

Continued on next page.

No. 5776-11/16

LA8638V

Continued from preceding page.

Pin Number

Pin Name

Pin Voltage

Equivalent Circuit

Description

CMP-RCT

Full-wave rectifier output for compressor
block (AC smoothing)

Indeterminate

(when there is

no signal)

MIC-OUT

Microphone amplifier output

TX-LVL-ADj

Pin for setting amplification for transmitter
output level switching

MIC-IN2

Microphone amplifier negative input

MIC-IN1

Microphone amplifier positive input

/2 power

supply

I/O Characteristics

Crosstalk Characteristics

Input level, V

-- dBV

Splatter Filter Frequency Characteristics

Input level, V

-- dBV

Current Drain --. V

Frequency, f -- kHz

Power supply voltage, V

-- V

Output level, V

-- dBV

Response -- dB

Crosstalk level, CT -- dBV

Current drain, I

= 2.4 V; resistance

TX-OUT (pin 23)

TX-DT-OUT (pin 23)

RX-OUT (pin 10)

TX (pin 23)

TX-MUTE (pin 23)

RX (pin 10)

RX-MUTE (pin 10)

BTL on

BTL off

Standby

No. 5776-12/16

LA8638V

Output Level

Gain Change Level Difference

Power Supply Voltage, -- V

Compander Gain Error

Power supply voltage, V

-- V

Output Distortion

Power supply voltage, V

-- V

Power supply voltage, V

-- V

BTL Power Amplifier Maximum Output Voltage

Receiver Muting Attenuation

Power supply voltage, V

-- V

Receiver (TX

RX) Crosstalk

Power supply voltage, V

-- V

Transmitter Crosstalk

Power supply voltage, V

-- V

Power supply voltage, V

-- V

Output level, V

-- dBV

Gain change level difference, GC -- dB

Compander gain error, GE -- dB

Total harmonic distortion, THD -- %

Maximum output voltage, V

-- Vp-p

Muting level -- dBV

Crosstalk level, CT -- dBV

TX (pin 23)

= 60 dBV

RX (pin 10)

= 20 dBV

RX (pin 10)

= 20 dBV

TX (pin 23)

= 60 dBV

TX-DATA (pin 23)

= 20 dBV

Switches gain between high and low levels.
Resistance at pin 9: 1 k

; Resistance

between pins 30 and 29: 4.7 k

Pins 13 and 14

Pin 10

Pin 13

Pin 10

Pin 14

1 kHz-BPF
TX-IN(28 pin): V

= 40dBV

No. 5776-13/16

LA8638V

Output Noise Level

Splatter Filter Cutoff Frequency

Power supply voltage, V

-- V

Splatter Filter Attenuation

Power supply voltage, V

-- V

Data Shaper Duty Cycle

Power supply voltage, V

-- V

Data Shaper Dead Zone

Power supply voltage, V

-- V

Current Drain

Power supply voltage, V

-- V

Output Level

Ambient temperature, Ta

°C

Gain Change Level Difference

Ambient temperature, Ta

°C

Ambient temperature, Ta

°C

Output level, V

-- dBV

Gain change level difference, GC -- dB

Current drain, I

-- mA

Minimum input level -- dBV

Duty cycle -- %

Cutoff frequency -- kHz

Output noise level -- dBV

Attenuation -- dB

TX (pin 23)

= 5 or 1 kHz;

resistance at pin 24
= 4.3 k

Att. = 3 dB down;
resistance at pin 24
= 4.3 k

BTL on

BTL off

Standby

RX (pin 10)

= 20 dBV

TX (pin 23)

= 60 dBV

TX-DATA (pin 23)

= 20 dBV

Switches gain between high and low levels.
Resistance at pin 9: 1 k

; Resistance

between pins 30 and 29: 4.7 k

No signal

No. 5776-14/16

LA8638V

Compander Gain Error

Temperature

Output Distortion

Temperature

BTL Distortion

Temperature

BTL Power Amplifier Maximum Output Voltage

Temperature

Ambient temperature, Ta -- °C

BTL Output Level

Temperature

Ambient temperature, Ta -- °C

Receiver Muting Attenuation

Temperature

Ambient temperature, Ta -- °C

Receiver (TX

RX) Crosstalk

Temperature

Ambient temperature, Ta -- °C

Transmitter Crosstalk

Temperature

Ambient temperature, Ta -- °C

Crosstalk level, CT -- dBV

Muting level -- dBV

Output level, V

-- dBV

Total harmonic distortion, THD -- %

Maximum output voltage, V

-- V

Total harmonic distortion, THD -- %

Compander gain error, GE -- dB

Pin 13

Pin 10

Pin 14

Pin 13

Pin 14

Pin 13

Pin 10

Pin 13

Pin 14

TX (pin 23)

V{IN} = 60 dBV

RX (pin 10)

V{IN} = 20 dBV

THD output = 1 %

No. 5776-15/16

LA8638V

Output Noise Level

Temperature

Splatter Filter Cutoff Frequency

Temperature

Ambient temperature, Ta -- °C

Splatter Filter Attenuation

Temperature

Ambient temperature, Ta -- °C

Receiver Maximum Input Level

Temperature

Ambient temperature, Ta -- °C

Transmitter Maximum Input Level

Temperature

Ambient temperature, Ta -- °C

Data Shaper Duty Cycle

Temperature

Ambient temperature, Ta -- °C

Data Shaper Dead Zone

Temperature

Ambient temperature, Ta -- °C

Minimum input level -- dBV

Duty cycle -- %

Maximum input level at pin 21 -- dBV

Maximum inputlevel at pin 5 -- dBV

Cutoff frequency -- kHz

Attenuation

Output noise level -- dBV

THD = 1% for output from pin 23

TX (pin 23)

TX-MUTE (pin 23)

RX (pin 10)

Att. = 3 dB down;
resistance at pin
24 = 4.3 k

THD = 1% for
output from pin 10

RX-MUTE (pin 10)

PS No. 5776-16/16

LA8638V

This catalog provides information as of April, 1998. Specifications and information herein are subject to change
without notice.

No products described or contained herein are intended for use in surgical implants, life-support systems, aerospace
equipment, nuclear power control systems, vehicles, disaster/crime-prevention equipment and the like, the failure of
which may directly or indirectly cause injury, death or property loss.

Anyone purchasing any products described or contained herein for an above-mentioned use shall:

Accept full responsibility and indemnify and defend SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and
distributors and all their officers and employees, jointly and severally, against any and all claims and litigation and all
damages, cost and expenses associated with such use:

Not impose any responsibility for any fault or negligence which may be cited in any such claim or litigation on
SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and distributors or any of their officers and employees
jointly or severally.

Information (including circuit diagrams and circuit parameters) herein is for example only; it is not guaranteed for
volume production. SANYO believes information herein is accurate and reliable, but no guarantees are made or implied
regarding its use or any infringements of intellectual property rights or other rights of third parties.

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