Datasheet LA4906 Datasheet (SANYO)

Page 1

Overview

The LA4906 is a BTL two-channel power amplifier for use in car audio systems. It uses a signal-following switching technique in the power supply for the amplifier output stage and a newly-developed nonlinear amplifier that features nonlinear characteristics in the signal system. These features hold increases in the number of external components to a minimum, and reduce power dissipation (and thus heat generation) in the practical operating region to about 1/2 that of earlier class B amplifier ICs. This can contribute significantly to miniaturization and weight reduction in the heat sink and to reduction of the heat generated within the end product case.

Features

• Power dissipation reduced by 50% (for music at average power levels, as compared to earlier Sanyo products)

• The number of required signal-following switching circuits has been reduced to just one circuit for two channels, reducing the number of external components.

• The output is a pure analog signal; no switching noise whatsoever appears on the output lines.

• Uses a single-voltage power supply from 8 to 18 V.

• Provides a full range of built-in protection circuits, including shorting of output pin to VCC, shorting of output pin to ground, overvoltage, and thermal shutdown protection.

• Built-in standby switch

• Clipping detection function

Package Dimensions

unit: mm

3160-SIP23HZ

Monolithic Linear IC

Ordering number : EN *5714

73097HA(OT) No. 5714-1/10

Preliminary

SANYO: SIP23HZ

[LA4906]

SANYO Electric Co.,Ltd. Semiconductor Bussiness Headquarters

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

17-W, 2-Channel BTL AF High-Efficiency

Power Amplifier for Car Audio Systems

LA4906

Parameter Symbol Conditions Ratings Unit

Maximum supply voltage

max1 With no signal, t = 1 minute 18 V

max2 16 V

Maximum output current I

Peak Per channel 4.5 A Allowable power dissipation Pd max With an arbitrarily large heat sink 37.5 W Operating temperature Topr –35 to +85 °C Storage temperature Tstg –40 to +150 °C

Specifications

Absolute Maximum Ratings at Ta = 25°C

Notes: 1. Set VCCand RLto be in the range where Pd max does not exceed 37.5 W.

2. The overvoltage protection circuit operates at V

= 26 V or higher.

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LA4906

Parameter Symbol Conditions

Ratings

Unit

min typ max

Quiescent current drain I

0 RL= ∞, VIN= 0 80 110 150 mA Standby current Ist 0 10 µA Voltage gain VG V

= 0 dBm 28 30 32 dB

Total harmonic distortion THD P

= 1 W, LPF = 30 kHz 0.07 0.2 %

Output power

1 THD = 10 %, RL = 4 Ω 14 17 W

2 THD = 10 %, RL = 2 Ω 25 W Output noise voltage V

Rg = 0, BPF = 20 Hz to 20 kHz 0.10 0.3 mVrms

Ripple rejection ratio SVRR

Rg = 0, V

CCR

= 0 dBm,

60 75 dB

BPF = 20 Hz to 20 kHz

Channel separation CH sep

Rg = 10 kΩ, V

= 0 dBm,

45 60 dB

BPF = 20 Hz to 20 kHz

Input resistance Ri 21 30 39 kΩ Output offset voltage VN offset Rg = 0 –200 +200 mV Standby on voltage V

STH

AMP = on, applied through a 10 kΩ resistor 3 V

Clipping detect off current I

DOFF

THD = 1 % 1 10 µA

Clipping detect on current I

DON

THD = 10 % 100 150 200 µA

Operating Characteristics

at Ta = 25°C, VCC= 13.2 V, RL= 4 Ω, f = 1 kHz, RG = 600 Ω, in the recommended circuit

Parameter Symbol Conditions Ratings Unit

Recommended supply voltage V

13.2 V

Allowable operating voltage range V

op 8 to 16 V Recommended load resistance R

4 Ω

Recommended load resistance range R

op 2 to 4 Ω

Operating Conditions at Ta = 25°C

Note: Set VCCand RLto be in the range where Pd max does not exceed 37.5 W.

Allowable power dissipation, Pd max – W

Heat sink thermal resistance,

θf – °C/W

Heat sink area, Sf – cm

Ambient temperature, Ta – °C

With an arbitrarily large heat sink

Al heat sink, t = 1.5 mm Tightening torque: 39 N·cm With silicone grease applied.

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No. 5714-3/10

LA4906

Technologies for Increased Efficiency Used in the LA4906

• Nonlinear amplifier The LA4906 adopts a nonlinear amplifier, which has the nonlinear characteristics shown in Figure 2, in the signal system. The LA4906 dispenses with the lower side switching regulator by using a low 2 V as the midpoint voltage instead of the 1/2 VCC used in normal amplifiers.

This nonlinear amplifier is basically formed from a differential amplifier that has a symmetrical negative feedback circuit. Although the BTL output stage positive and reverse phase output waveforms have a half-wave waveform that, when referenced to ground, is expanded and compressed as shown in Figure 3, the combined output waveform at the load terminals is identical to that of earlier products.

• Signal-following switching technique The LA4906 uses a switching regulator for the power supply for the amplifier output stage. The LA4906 significantly reduces power dissipation by having the switching regulator output voltage follow the signal. Also, the LA4906 restricts the number of switching regulators required to just one circuit even though it implements a BTL 2-channel amplifier by using the switching regulator in combination with the nonlinear amplifier described below. (See Figure 1.)

Figure 1 Overview Block Diagram

Figure 2 Nonlinear Amplifier

Input/Output Characteristics

Figure 3 Output Waveforms

Figure 4

RL = 4 Ω f = 1 kHz Rg = 600 Ω With both channels driven. Calculated at Pd = VCC × ICC – 2 P

Regulator output

Amplifier

output

stage

Nonlinear

amplifier

Loss in the output transistor

Regulator output (point C)

Positive phase output (point A) Center point Ground

Reverse phase output (point B) Center point Ground

Waveform between the outputs (Between A and B)

Power dissipation, Pd – W

Output power, PO– W

High-efficiency

LA4906

Earlier SANYO products (class B amplifiers)

Page 4

Equivalent Circuit Block Diagram

No. 5714-4/10

LA4906

Pin Voltages (At VCC= 13.2 V, with 5 V applied to STBY through a 10 kΩ resistor, using a digital voltmeter)

Pin No. 1 2 3 4 5 6 7 8 Pin IN2 Pre - GND IN1 BEEP PWR - GND 1 –OUT1 +OUT1 C Pin voltage (V) 1.36 0 1.36 1.36 0 2.03 2.03 13.0

Pin No. 9 10 11 12 13 14 15 16 Pin C V

(SW) SW OUT1 SW OUT2 SW E SE B SW - GND

Pin voltage (V) 3.92 13.2 13.2 3.70 3.70 3.73 4.0 0

Pin No. 17 18 19 20 21 22 23 Pin +OUT2 –OUT2 PWR - GND2 D. C STAND-BY DDL OUT ON-TIME Pin voltage (V) 2.03 2.03 0 12.1 3.21 0 2.81

Standby switch

Switching regulator block

Switch

driver

Standby switch

Ripple filter

(Tokin Co. Ltd.)

(OS capacitor)

* = Polyester film capacitors

D1 SB40-05J Flywheel diode

Amplifier output stage

Input amplifier

Nonlinear amplifier/output stage

TR1 Switching transistor 2SD1668, class S

Muting circuit used

at power on

Popping noise

prevention circuit

Power supply/ground shorting protection circuit Overvoltage/thermal protection circuit

Beep amplifier

4 to 2 Ω

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No. 5714-5/10

LA4906

Sample Printed Circuit Board

1. External component descriptions

C1 and C2

· Input capacitors. A value of 2.2 µ F is recommended for these capacitors. Note that the low-frequency area

characteristics can be adjusted by changing fL, which is determined by the values of C1 and C2. However, due to impulse (pop) noise considerations, the value of C1 and C2 should not exceed 3.3 µF when C4 is 22 µF.

· Beep amplifier input capacitor. A value the same as that of C1 and C2 is used. If the beep function is not used, connect

the beep input to PRE-GND through C3.

· Set the amplifier turn-on time. A value of 22 µF is recommended. (This will result in a turn-on time of about 0.7

second.) The on time is proportional to the value of this capacitor, and any value may be used. However, due to impulse (pop) noise considerations, a value of 22 µF or larger should be used.

C5, C6, C7, and C8

· Oscillation prevention capacitors. Polyester film (Mylar) capacitors with good temperature characteristics must be used.

(These are used together with R1, R2, R3, and R4.) We recommend values of 0.1 µ F or higher for these capacitors since the stability will differ somewhat depending on the printed circuit board layout actually used.

· Decoupling capacitor (ripple filter)

C10

· Power-supply capacitor

C11

· Oscillation prevention capacitor for the switching regulator. A value of 1500 pF is recommended.

C12

· Switching regulator output smoothing capacitor. The LA4906 adopts a self-excited switching regulator technique. The

value of this capacitor must be optimized, since it influences both the self-excitation stability and the regulator efficiency. We recommend using a 2.2-µ F 25-V OS (Organic Semiconductor) capacitor with a low series resistance and good temperature characteristics. Note that for the same reason a 2.2-Ω 1/2-W resistor should be used for the associated resistor R6.

· Standby switch current limiter resistor. A value of 10 kΩ is recommended. (When the voltage applied to the standby

switch is in the range 3 to 13.2 V.) Note that this resistor cannot be removed from this circuit.

Page 6

See the “Standby Function” section elsewhere in this document. TR1

· External switching transistor. The 2SD1668 (rank S) is recommended.

If the application supports a load resistance RL of 4 Ω, a 2SD1667 (rank S) may be used. A heat sink must be provided for this transistor, as well as for the IC itself.

· Flywheel diode used to absorb energy from the coil. The SB40-05J, which is a Schottky barrier diode with a low VF, is recommended. If the application supports a load resistance RL of 4 Ω, an SB10-05A2 may be used. A heat sink must be provided for this diode, as well as for the IC itself.

· The Tokin Co., Ltd.-made HP-022Z [180 µH] (or the HP-011Z [200 µH] for 4-Ω applications) is recommended.

2. IC internal characteristics and other notes

Switching regulator

· The LA4906 includes a signal-following self-excited switching regulator to reduce power dissipation. The selfexcitation frequency with no input signal is about 100 kHz.

· To avoid spurious signal interference within the end product case, it is desirable to separate the tuner block from the amplifier block by as far as possible. When designing the printed circuit board pattern, make the lines associated with the switching regulator external components as short and as wide as possible.

· To prevent degradation of the LA4906 characteristics, separate the switching regulator external components from the IC inputs (the input block pattern, the input capacitors, and the beep amplifier capacitor) by at least 1.5 cm.

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LA4906

Standby function

· Pin 21 is the standby switching pin. The amplifier is turned on by applying a voltage of over 3 V to pin 21 through an external resistor (R1).

· If the standby switch applied voltage will exceed 13.2 V, then the current flowing into pin 5 must be held to under 500 µ A. Use the following formula to determine the value of R1 that meets this condition.

R1 =

applied voltage – 1.4 V

– 10 kΩ

500 µA

BEEP pin (pin 4)

· If the BEEP pin is used, use the smallest value of R102 (see figure) possible (but note that this value must be under 100 Ω) to prevent degradation of the IC's output noise voltage (VNO) characteristics.

Protection circuits

· The LA4906 includes an on-chip thermal protection circuit to prevent destruction of or damage to the IC if abnormal heating occurs. If, due to an inadequate heat sink or other reason, the IC junction temperature (Tj) reaches or exceeds 160°C, the output is gradually attenuated by the operation of the thermal protection circuit.

The overvoltage protection circuit operates if the VCCvoltage exceeds 20 V.

· While the LA4906 includes a power supply/ground short protection circuit, it does not include a load shorting protection circuit. The idea behind this design is that the thermal shutdown protection circuit will protect the IC itself if the load is shorted. However, since a load short will also cause temperature increases in the external transistor and coil, care is required in handling this case.

Other notes

· Pin 22 is not connected electrically to any other points within the package.

Pin 21 IC Internal Equivalent Circuit

Applied standby voltage

500 µA or less

Beep signal

About 1.4 V (2VBE)

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No. 5714-7/10

LA4906

Quiescent current, I

CCO

– mA

Output power, P

– W

Output pin voltage, V

– V

Output power, P

– W

Total harmonic distortion, THD – %

Response – dB

Output power, P

– W

Total harmonic distortion, THD – %

Supply voltage, VCC–V

Overvoltage protection circuit operation

Supply voltage, VCC–V

Output power, PO– W

Input frequency, f – Hz

Output power, PO– W

Supply voltage, VCC–V

Input level, V

– mV rms

Both channels operating

peak exceeded

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LA4906

Output power, P

– W

Channel separation, CHsep – dB

Ripple rejection ratio, SVRR – dB

Power dissipation, Pd – W

Output noise voltage, V

– mV rms

Ripple rejection ratio, SVRR – dB

Current drain, I

– A

Input frequency, f – Hz

Input resistance, Rg – Ω

Ripple frequency, f

– Hz

Output power, P

– W

Output power, PO– W

Power supply ripple current voltage, V

CCR

– Vrms

Supply voltage, VCC–V

Input frequency, f – Hz

Both channels operating

Using a 1-µF power-supply capacitor

Using a 1-µF power-supply capacitor Calculate SVRR from the following formula:SVRR = 20 log (VO/VCCR)

Pd for the IC itself

Pd for the external transistor

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No. 5714-9/10

LA4906

With VST applied to pin 21 through a 10-kΩ resistor)

· The time until the amplifier turns on after VSTis applied

Power dissipation, Pd – W

Quiescent current, I

CCO

– mA

Total harmonic distortion, THD – %

Regulator oscillator frequency, f

OSC

– kHz

Output power, P

– W

Output pin voltage, V

– V

Output power, PO– W

Supply voltage, VCC– V

Ambient temperature, Ta – °C

Applied standby pin voltage, VST– V

Ambient temperature, Ta – °C

Output power, P

– W

Both channels operating

Pd for the external transistor

Pd for the IC itself

(Tokin Co., Ltd.)

(OS capacitor)

In the recommended circuit

With VST applied to the standby pin (pin 21) through a 10-kΩ resistor

Page 10

No. 5714-10/10

LA4906

This catalog provides information as of July, 1997. 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: 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.