Ordering number : EN5776
Monolithic Linear IC
LA8638V
Low-voltage Compander IC
for Cordless Telephones
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.
speaker with a load of 2 kΩ
• 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
[LA8638V]
Functions
• Transmitter circuits: compressor, microphone amplifier,
limiter (IDC), muting, output level changes to userspecified 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
SANYO: SSOP30
Specifications
Maximum Ratings at Ta = 25°C
Parameter
Maximum power supply voltage
Symbol
Conditions
VCC max
Maximum power dissipation
Pd max
Ta ≤ 75°C
Ratings
Unit
7.0
V
100
mW
Operating temperature
Topr
–20 to +75
°C
Storage temperature
Tstg
–40 to +125
°C
Ratings
Unit
Operating Conditions at Ta = 25°C
Parameter
Symbol
Recommended power supply voltage
VCC
Operating power supply voltage range
VCCop
Conditions
2.4
V
1.8 to 5.5
V
SANYO Electric Co.,Ltd. Semiconductor Bussiness Headquarters
TOKYO OFFICE Tokyo Bldg., 1-10, 1 Chome, Ueno, Taito-ku, TOKYO, 110-8534 JAPAN
40398RM (OT) No. 5776-1/16
LA8638V
Electrical Characteristics at Ta = 25°C, VCC = 2.4 V, fIN = 1 kHz
Parameter
Symbol
Conditions
Ratings
min
typ
max
Unit
Current drain with no signal
ICCO
No signal
3.0
5.4
7.6
mA
Standby current
ISTBY
Standby mode, No signal
0.4
0.7
0.95
mA
dBV
[Transmitter block] Vinrefc = –60 dBV = 0 dB, microphone amplifier gain = 40 dB, RL = 15 kΩ
Output level
VOc
VIN = Vinrefc = 0 dB
–18.1
–16.1
–14.1
Gain change level
GCc
VIN = –10 dB
3.5
4.0
4.4
dB
Gain error
GEc
VIN = –40 dB
–2.0
–0.7
+1.0
dB
0.45
1.0
%
1.8
4.5
mVrms
0.88
1.05
1.23
Vp-p
40
46
12.0
16.5
Total harmonic distortion
THDc
VIN = 0 dB
Output noise voltage
VNOc
Rg = 620Ω, f = 20 to 20 kHz
Limiting voltage
Microphone amplifier maximum voltage gain
Low pass filter attenuation
VLT
VIN = +30 dB, 1 kHz BPF
VG max
Lalt
fIN = 5 kHz; fifth-order Butterworth function
filter (fc = 3.35 kHz)
dB
25.0
dB
Muting attenuation
ATTc
VIN = +30 dB, 1 kHz BPF
–83
–65
dBV
Crosstalk level
CTc
RX—VIN = –10 dBV, 1 kHz BPF
–61
–50
dBV
–18.8
–16.3
–13.8
dBV
6.0
7.1
8.4
dB
–1.5
+0.3
+2.0
dB
[Receiver block] Vinrefe = –20 dBV = 0 dB, RL = 15 kΩ
Output level
VOe
VIN = Vinrefe = 0 dB
Gain change level
GCe
VIN = 0 dB
Gain error
GEe
VIN = –30 dB
Output noise voltage
VNOe
Rg = 620 Ω, f = 20 to 20 kHz
Muting attenuation
ATTe
VIN = +10 dB, 1 kHz BPF
Crosstalk level
CTe
TX—VIN = –40 dBV, 1 kHz BPF
50
100
µVrms
–100
–80
dBV
–83
–65
dBV
[BTL amplifier] RL = 2 kΩ
Maximum output voltage
VObtl
Total harmonic distortion
THDbtl
THD = 3%
3.2
VIN = –5 dBV
4.2
0.4
Vp-p
1.0
%
[Data shaper] VIN = –20 dBV, RL = 100 kΩ
Duty factor
DUTY
43
50
57
Dead zone
UNSN
–39.0
–34.5
–30.0
2.2
2.38
Output “H” level
VH
Output “L” level
VL
0.12
%
dBV
V
0.3
V
[Digital input characteristics]
Input “H” level 1
VIH1
Pins 17, 18, 20, and 22
Input “L” level 1
VIL2
Pins 17, 18, 20, and 22
Input “H” level 2
VIH2
Pin 19
Input “L” level 2
VIL2
Pin 19
0.6 VCC
V
0.25 VCC
1.3
V
V
0.3
V
No. 5776-2/16
LA8638V
Block Diagram
No. 5776-3/16
LA8638V
Sample Application Circuit
No. 5776-4/16
LA8638V
Test Circuit
No. 5776-5/16
LA8638V
Usage Notes
1. Internal Reference Voltages
The chip uses the following reference voltages internally.
Pin 29 (VREF) Power supply voltage follower (approximately 0.5 VCC)
Pin 4 (VREF2) 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 finetune 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 RB so that the total DC
resistance between pins 4 and 5 is on the order of 120 kΩ 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.
Table 1. Standardized Circuit Constants
Lowpass filter type
X1
X2
Second-order Butterworth function
0.7071
1.4142
X3
—
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
The Bessel functions for cutoff frequencies do not incorporate the notion of 3dB attenuation. The 3-dB attenuation frequency for the second-order function
is 1.38 fc; for the third-order function, 1.75 fc.
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
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:
VCC (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 kΩ, 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 kΩ.
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
Pin 17
Pin 18
SUB-CNT1
SUB-CNT2
Mode
OPEN/HIGH
OPEN/HIGH
Standby
OPEN/HIGH
LOW
Receiver muted
LOW
OPEN/HIGH
Normal receiver output levels
LOW
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.
No. 5776-7/16
LA8638V
Graph 2. Transmitter Gain Change Level vs. External Resistance
Level difference (dB)
Cutoff frequency (kHz)
Graph 1. Splatter Filter Cutoff Frequency vs. External Resistance
External resistance (kΩ)
External resistance (kΩ)
Level difference (dB)
Graph 3. Receiver Gain Change Level vs. External Resistance
External resistance (kΩ)
No. 5776-8/16
LA8638V
Pin Descriptions
Pin Number
Pin Name
Pin Voltage
Equivalent Circuit
Description
1
GND
2
1/2 VCC
VCC/2
Resistance voltage divider pin
29
VREF
VCC/2
Reference voltage for all circuits except
receiver block
3
CMP-NF
VCC/2
AC feedback control for compressor's
summing amplifier DC gain: 1 AC gain:
Infinite
4
DT-VREF
1.25 V
Reference voltage for receiver block This
supplies the bias voltage for pin 5.
5
RX-IN
1.25 V power
supply
6
RX-FIL-OUT
1.25 V
Filter buffer output
7
EXP-IN
VCC/2
Expander input. Voltage-current converter
input. Full-wave rectifier input.
8
EXP-RCT
Indeterminate
(when there is
no signal)
Full-wave rectifier output for expander block
(AC smoothing)
9
RX-ATT-ADJ
0.03 V
Pin for setting attenuation for receiver output
level switching
10
RX-OUT
VCC/2
Receiver block output
Ground for all circuits except BTL amplifier
Filter buffer input
Continued on next page.
No. 5776-9/16
LA8638V
Continued from preceding page.
Pin Number
Pin Name
Pin Voltage
Equivalent Circuit
Description
12
BTL-GND
11
BTL-IN
VCC/2
BTL amplifier input
13
BTL-OUT1
VCC/2
BTL amplifier reversed output
14
BTL-OUT2
VCC/2
BTL amplifier non-reversed output
15
VCC
16
FSK-OUT
Indeterminate
(when there is
no signal)
17
SUB-CNT1
VCC
18
SUB-CNT2
VCC
20
TX-MUTE
VCC
22
TX-LVL-CNT
VCC
19
BTL-CNT
VCC + 0.65
—————
2
21
TX-DATA-IN
VCC /1.6
Transmitter data input
23
TX-OUT
VCC /1.6
Transmitter output
24
FREQ-ADJ
0.01 V
Ground for BTL amplifier
Power supply pin
Comparator output (open collector output)
Internal operating mode control pins. All four
have identical structures.
BTL amplifier operation control pins
Pin for setting cutoff frequency of splatter
filter
Continued on next page.
No. 5776-10/16
LA8638V
Continued from preceding page.
Pin Number
Pin Name
Pin Voltage
Equivalent Circuit
25
CMP-RCT
Indeterminate
(when there is
no signal)
26
MIC-OUT
VCC/2
Microphone amplifier output
27
MIC-IN2
VCC/2
Microphone amplifier negative input
28
MIC-IN1
VCC/2 power
supply
Microphone amplifier positive input
30
TX-LVL-ADj
VCC/2
Full-wave rectifier output for compressor
block (AC smoothing)
Pin for setting amplification for transmitter
output level switching
3)
23
in
T-
10)
O
UT
(p
U
-O
TX
)
n2
-OU
T(
pin
RX
Crosstalk level, CT — dBV
Crosstalk Characteristics
TX
-D
Output level, VO — dBV
I/O Characteristics
pi
T(
Description
RX → TX
(pin 23)
)
E (pin 23
TX-MUT
TX → RX (pin 10)
RX-MUTE (pin
Input level, VIN — dBV
Input level, VIN — dBV
Splatter Filter Frequency Characteristics
Current Drain —. VCC
10)
VCC = 2.4 V; resistance
Response — dB
Current drain, ICC — mA
BTL on
BTL off
Standby
Frequency, f — kHz
Power supply voltage, VCC — V
No. 5776-11/16
LA8638V
RX (pin 10) ← VIN = –20 dBV
Gain Change Level Difference — VCC
Gain change level difference, GC — dB
TX (pin 23) ← VIN = –60 dBV
Switches gain between high and low levels.
Resistance at pin 9: 1 kΩ; Resistance
between pins 30 and 29: 4.7 kΩ
Power supply voltage, VCC — V
Compander Gain Error — VCC
Output Distortion — VCC
Total harmonic distortion, THD — %
Power Supply Voltage, — VCC V
Compander gain error, GE — dB
Output level, VO — dBV
Output Level — VCC
RX (pin 10) ← VIN = –20 dBV
TX (pin 23) ← VIN = –60 dBV
TX-DATA (pin 23) ← VIN = –20 dBV
Power supply voltage, VCC — V
Power supply voltage, VCC — V
Receiver Muting Attenuation — VCC
Muting level — dBV
Maximum output voltage, VO — Vp-p
BTL Power Amplifier Maximum Output Voltage — VCC
Power supply voltage, VCC — V
Pins 13 and 14
Pin 10
Power supply voltage, VCC — V
Transmitter Crosstalk — VCC
Receiver (TX → RX) Crosstalk — VCC
Pin 13
Pin 10
Pin 14
Power supply voltage, VCC — V
Crosstalk level, CT — dBV
Crosstalk level, CT — dBV
1 kHz-BPF
TX-IN(28 pin): VIN = –40dBV
Power supply voltage, VCC — V
No. 5776-12/16
LA8638V
Output Noise Level — VCC
Splatter Filter Cutoff Frequency — VCC
Output noise level — dBV
TX (pin 23)
TX (pin 23)
TX (pin 23)
Cutoff frequency — kHz
Att. = 3 dB down;
resistance at pin 24
= 4.3 kΩ
Power supply voltage, VCC — V
Power supply voltage, VCC — V
Splatter Filter Attenuation — VCC
Data Shaper Duty Cycle — VCC
Duty cycle — %
Attenuation — dB
fIN = 5 or 1 kHz;
resistance at pin 24
= 4.3 kΩ
Power supply voltage, VCC — V
Power supply voltage, VCC — V
Data Shaper Dead Zone — VCC
Current Drain — Ta
Current drain, ICC — mA
BTL on
BTL off
Standby
Power supply voltage, VCC — V
Ambient temperature, Ta — °C
Output Level — Ta
Gain Change Level Difference — Ta
RX (pin 10) ← VIN = –20 dBV
TX (pin 23) ← VIN = –60 dBV
TX-DATA (pin 23) ← VIN = –20 dBV
Ambient temperature, Ta — °C
Gain change level difference, GC — dB
Output level, VO — dBV
Minimum input level — dBV
No signal
Switches gain between high and low levels.
Resistance at pin 9: 1 kΩ; Resistance
between pins 30 and 29: 4.7 kΩ
Ambient temperature, Ta — °C
No. 5776-13/16
LA8638V
Output Distortion — Temperature
Compander gain error, GE — dB
Total harmonic distortion, THD — %
Compander Gain Error — Temperature
Ambient temperature, Ta — °C
TX (pin 23) ← V{IN} = –60 dBV
RX (pin 10) ← V{IN} = –20 dBV
Ambient temperature, Ta — °C
BTL Distortion — Temperature
BTL Power Amplifier Maximum Output Voltage — Temperature
Pin 13
Pin 14
Maximum output voltage, VO — VPP
Total harmonic distortion, THD — %
THD output = 1 %
Ambient temperature, Ta — °C
Ambient temperature, Ta — °C
BTL Output Level — Temperature
Receiver Muting Attenuation — Temperature
Pin 14
Muting level — dBV
Pin 13
Pin 13
Pin 10
Ambient temperature, Ta — °C
Ambient temperature, Ta — °C
Receiver (TX → RX) Crosstalk — Temperature
Transmitter Crosstalk — Temperature
Pin 13
Pin 10
Pin 14
Ambient temperature, Ta — °C
Crosstalk level, CT — dBV
Crosstalk level, CT — dBV
Output level, VO — dBV
Pin 14
Ambient temperature, Ta — °C
No. 5776-14/16
LA8638V
Output Noise Level — Temperature
Splatter Filter Cutoff Frequency — Temperature
TX (pin 23)
TX-MUTE (pin 23)
Cutoff frequency — kHz
Output noise level — dBV
Att. = 3 dB down;
resistance at pin
24 = 4.3 kΩ
RX (pin 10)
RX-MUTE (pin 10)
Ambient temperature, Ta — °C
Receiver Maximum Input Level — Temperature
Attenuation — dB
Maximum inputlevel at pin 5 — dBV
Ambient temperature, Ta — °C
Splatter Filter Attenuation — Temperature
Ambient temperature, Ta — °C
THD = 1% for
output from pin 10
Ambient temperature, Ta — °C
Transmitter Maximum Input Level — Temperature
Data Shaper Duty Cycle — Temperature
Duty cycle — %
Maximum input level at pin 21 — dBV
THD = 1% for output from pin 23
Ambient temperature, Ta — °C
Ambient temperature, Ta — °C
Minimum input level — dBV
Data Shaper Dead Zone — Temperature
Ambient temperature, Ta — °C
No. 5776-15/16
LA8638V
■ 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:
➀ 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:
➁ 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.
This catalog provides information as of April, 1998. Specifications and information herein are subject to change
without notice.
PS No. 5776-16/16