LA4708.PDF

Ordering number: EN5245A

Monolithic Linear IC

LA4708

20 W 2-channel BTL AF Power Amplifier

for Car Stereos

Overview

Package Dimensions

unit: mm

3109-SIP18H

The LA4708 is a BTL two-channel power IC for car audio

developed in pursuit of excellent sound quality. Low-region

frequency characteristics have been improved through the use

of a new NF capacitorless circuit, and crosstalk which causes

‘‘muddy’’ sound has been reduced by improving both circuit

and pattern layout. As a result, the LA4708 provides powerful

bass and clear treble. In addition, the LA4708 features on-chip

protectors and standby switch. The LA4708 is also

pin-compatible with the LA4705NA (car stereo-use 17 W

two-channel power IC), and can be substituted for the

LA4705NA for higher power. (When the board is shared, pins

1 and 9 must be left open.)

[LA4708]

Features

. High power: supports total output of 30 W + 30 W

(V CC = 13.2 V, THD = 30%, R L =4

SANYO : SIP18H

. Designed for excellent sound quality

(f L < 10 Hz, f H = 130 kHz)

. Any on time settable by external capacitor

. Less pop noise

. Standby switch circuit on chip (microprocessor supported)

. Various protectors on chip

(output-to-ground short/output-to-V CC short/

load short/overvoltage/thermal shutdown circuit)

Any and all SANYO products described or contained herein do not have specifications that can handle

applications that require extremely high levels of reliability, such as life-support systems, aircraft’s

control systems, or other applications whose failure can be reasonably expected to result in serious

physical and/or material damage. Consult with your SANYO representative nearest you before using

any SANYO products described or contained herein in such applications.

SANYO assumes no responsibility for equipment failures that result from using products at values that

exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other

parameters) listed in products specifications of any and all SANYO products described or contained

herein.

SANYO Electric Co.,Ltd. Semiconductor Bussiness Headquarters

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

93096HA(II)/13096HA(II) No.5245-1/9

. Supports R L =2W(P O = 30 W when V CC = 13.2 V,

THD = 10%)

)

. NF capacitorless

LA4708

Specifications

Maximum Ratings at Ta = 25°C

Parameter

Symbol

Conditions

Ratings

Unit

Maximum supply voltage

V CC max 1 No signal,t=60s

V CC max 2

Surge supply voltage

V CC surge t % 0.2 s, single giant pulse

Maximum output current

I O peak Per channel

4.5

Allowable power dissipation

Pd max Arbitrarily large heat sink

37.5

Operating temperature

Topr

–35 to +85

°C

Storage temperature

Tstg

–40 to +150

°C

* Set V CC ,R L in a range that does not exceed Pd max = 37.5 W

Operating Conditions at Ta = 25°C

Parameter

Symbol

Conditions

Ratings

Unit

Recommended supply voltage

V CC

13.2

Operating voltage range

V CC op Range where Pd max is not exceeded

9 to 16

Recommended load resistance

R L

Recommended load resistance range

R L op

2to4

Operating Characteristics at Ta = 25°C, V CC = 13.2 V, R L =4

,f=1kHz, Rg = 600

Parameter

Symbol

Conditions

min typ max Unit

Quiescent current

I CCO

70 150 250 mA

Standby current

Ist

10 60 µA

Voltage gain

38 40 42 dB

Total harmonic distortion

THD P O = 2 W

0.07 0.4 %

P O 1 THD = 10%

16 20

Output power

P O 2 THD = 10%, V CC = 14.4 V

P O 3 THD = 10%, R L =2

Output offset voltage

V N offset Rg = 0

–300

+300 mV

Output noise voltage

V NO Rg = 0, B.P.F. = 20 Hz to 20 kHz

0.1 0.5 mVrms

Ripple rejection ratio

SVRR Rg = 0, f R = 100 Hz, V R = 0 dBm

40 50

Channel separation

CHsep Rg = 10 k W ,V O = 0 dBm

50 60

Input resistance

r i

21 30 39 k

Standby pin applied voltage

Vst Amp on, applied through 10 k W

2.5

V CC V

Arbitrarily large heat sink

Al heat sink, t = 1.5 mm

Tightening torque 39 N c cm

With silicone grease applied

Ambient temperature, Ta — °C

Heat sink area, S f —cm 2

No.5245-2/9

LA4708

Equivalent Circuit Block Diagram

Pins 1,9 : Don’t use

Pin 10 : No connection

Each Pin Voltage

V CC = 13.2 V, 5 V applied through STBY = 10 kW,R L =4W,Rg=0

Pin No.

Name

IN1

Pre-GND

STBY

ON TIME

Pin voltage (V)

0.29

1.58

6.55

3.2

2.28

Pin No.

Name

IN2

POP

–

N.C

V CC 2

–OUT 2

Pin voltage (V)

1.58

2.08

0.29

13.2

6.5

Pin No.

Name

PWR–GND 2

+OUT 2

+OUT 1

PWR–GND 1

–OUT 1

V CC 1

Pin voltage (V)

6.5

13.2

No.5245-3/9

LA4708

Sample Print Pattern

Copper foil area 90

105 mm 2

Description of External Components

C1, C4

Input capacitors

2.2 µF is recommended. f L can be varied by C1, C4 capacitances to adjust the

bass range.

Decoupling capacitor

(ripple filter)

Amplifier on time setting

capacitor

Approximately 0.8 second for 33 µF. Since the on time is proportional to this

capacitance, it can be set as desired by varying this capacitance.

(Refer to the characteristics curve.)

C5 Power supply capacitor

C6, C7, C8, C9 Oscillation blocking capacitors Use polyester film capacitors (Mylar capacitors) with good temperature

characteristics. (R2, R3, R4, and R5 used jointly.) Since stability may be

affected slightly by the pattern layout, etc., 0.1 µF or more is recommended.

Standby switch current limiting

resistor

is recommended (when the applied voltage for the standby switch is

2.5 V to 13.2 V). This resistor cannot be removed.

No.5245-4/9

10 k

LA4708

Features of IC Inside and Usage Notes

Standby function

. Pin 5 is the standby switch pin. The amplifier is turned on by applying approximately 2.5 V or more to this pin through an

external resistor (R1).

R1 =

Applied voltage – 1.4 V

–10kW

500 µA

500 µA or less

Pin 5 Equivalent

circuit internal IC

Standby

applied voltage

About 1.4 V

(2V BE )

Mute function

. Pin 6 is the connector for the capacitor that determines the on time in order to prevent pop noise. By grounding this pin, the

amplifier can implement mute operation. In this case, the recovery time depends on C3.

How to reduce pop noise

. Although the LA4708 reduces pop noise, an electrolytic capacitor of between 0.47 and 2.2 µF can be connected between pin 8

and the pre-GND to further reduce pop noise that occurs when power supply is turned on/off (standby switch on/off). The larger

the capacitance, the lower the frequency of pop noise, and it is barely audible, but sound residue of the sound signal is liable to

linger when power is turned off. Pin 8 is the bias pin for the output amplifier and normally is left open.

Protectors

. In an output-to-ground and output-to-V CC short protector system configuration, if a DC resistor is connected between amplifier

output pin and GND, the protector may operate, causing the amplifier not to start operating. Therefore, as a general rule, no DC

resistor should be connected between amplifier output pin and GND.

. Also be fully careful of handling other protectors built in the LA4708.

Miscellaneous

. Since pins 1 and 9, which are unused, are connected internally, they must be left open.

No.5245-5/9

. If voltage in excess of 13.2 V is to be applied to the standby switch, calculate the value of R1 using the following formula so

that the current flowing into pin 5 is 500 µA or less:

. In order to prevent damage or degradation which may be caused by abnormally heated IC, the LA4708 has a thermal shutdown

protector. Accordingly, if the IC junction temperature (Tj) climbs to around 170 to 180°C due to inadequate heat dissipation, the

thermal shutdown protector will operate to control the output gradually into attenuation.

. Pin 10 is an NC pin (no internal connection).

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