Ordering number : EN *5714

Monolithic Linear IC

LA4906
17-W, 2-Channel BTL AF High-Efficiency
Power Amplifier for Car Audio Systems
Preliminary

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

• Provides a full range of built-in protection circuits,
The LA4906 is a BTL two-channel power amplifier for
including shorting of output pin to VCC, shorting of
use in car audio systems. It uses a signal-following
output pin to ground, overvoltage, and thermal
switching technique in the power supply for the amplifier
shutdown protection.
output stage and a newly-developed nonlinear amplifier
• Built-in standby switch
that features nonlinear characteristics in the signal system.
• Clipping detection function
These features hold increases in the number of external
components to a minimum, and reduce power dissipation Package Dimensions
(and thus heat generation) in the practical operating region
unit: mm
to about 1/2 that of earlier class B amplifier ICs. This can
contribute significantly to miniaturization and weight 3160-SIP23HZ
reduction in the heat sink and to reduction of the heat
generated within the end product case. [LA4906]

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.

SANYO: SIP23HZ

Specifications
Absolute Maximum Ratings at Ta = 25°C
Parameter Symbol Conditions Ratings Unit
VCC max1 With no signal, t = 1 minute 18 V
Maximum supply voltage
VCC max2 16 V
Maximum output current IO 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
Notes: 1. Set VCC and RL to be in the range where Pd max does not exceed 37.5 W.
2. The overvoltage protection circuit operates at VCC = 26 V or higher.

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73097HA(OT) No. 5714-1/10
 LA4906

Operating Conditions at Ta = 25°C

Parameter Symbol Conditions Ratings Unit
Recommended supply voltage VCC 13.2 V
Allowable operating voltage range VCC op 8 to 16 V
Recommended load resistance RL 4 Ω
Recommended load resistance range RL op 2 to 4 Ω

Note: Set VCC and RL to be in the range where Pd max does not exceed 37.5 W.

Operating Characteristics at Ta = 25°C, VCC = 13.2 V, RL = 4 Ω, f = 1 kHz, RG = 600 Ω, in the recommended circuit
Ratings
Parameter Symbol Conditions Unit
min typ max
Quiescent current drain ICC0 RL = ∞, VIN = 0 80 110 150 mA
Standby current Ist 0 10 µA
Voltage gain VG VO = 0 dBm 28 30 32 dB
Total harmonic distortion THD PO = 1 W, LPF = 30 kHz 0.07 0.2 %
PO1 THD = 10 %, RL = 4 Ω 14 17 W
Output power
PO2 THD = 10 %, RL = 2 Ω 25 W
Output noise voltage VNO Rg = 0, BPF = 20 Hz to 20 kHz 0.10 0.3 mVrms

Ripple rejection ratio SVRR Rg = 0, VCCR = 0 dBm, 60 75 dB

BPF = 20 Hz to 20 kHz

Channel separation CH sep Rg = 10 kΩ, VO = 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 VSTH AMP = on, applied through a 10 kΩ resistor 3 VCC V
Clipping detect off current IDOFF THD = 1 % 1 10 µA
Clipping detect on current IDON THD = 10 % 100 150 200 µA

With an arbitrarily large heat sink

Al heat sink, t = 1.5 mm
Allowable power dissipation, Pd max – W

Tightening torque: 39 N·cm

Heat sink thermal resistance, θf – °C/W

With silicone grease applied.

Ambient temperature, Ta – °C Heat sink area, Sf – cm2

No. 5714-2/10
 LA4906

Technologies for Increased Efficiency Used in the LA4906

• Signal-following switching technique Regulator
output
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 Nonlinear
amplifier
Amplifier
Figure 1.) output
stage

Figure 1 Overview Block Diagram

• 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.
Figure 2 Nonlinear Amplifier
Input/Output Characteristics
Regulator output (point C)
Loss in the output
transistor

Positive phase RL = 4 Ω
output (point A) f = 1 kHz
Center point Rg = 600 Ω
Ground With both channels
driven.
Regulator output (point C) Calculated at Pd =
Power dissipation, Pd – W

VCC × ICC – 2 PO

Earlier SANYO
products (class
Reverse phase B amplifiers)
output (point B)
Center point
Ground

Waveform between High-efficiency

the outputs LA4906
(Between A and B)

Output power, PO – W

Figure 4

Figure 3 Output Waveforms

No. 5714-3/10
 LA4906

Equivalent Circuit Block Diagram

Standby
switch
Standby switch Switching
regulator
block
* TR1
Ripple filter Switch
Switching transistor
driver
2SD1668, class S

D1
(Tokin Co. Ltd.) SB40-05J
* Flywheel diode

(OS capacitor)

Amplifier output stage

Input amplifier
Nonlinear amplifier/output stage

4 to 2 Ω

Beep amplifier
Power supply/ground shorting
protection circuit * = Polyester film capacitors
Overvoltage/thermal
protection circuit

Input amplifier
4 to 2 Ω

Nonlinear amplifier/output stage

Muting circuit used Popping noise

at power on prevention circuit

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 VCC VCC (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

No. 5714-4/10
 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.
C3
· 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.
C4
· 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 µF or higher for these capacitors
since the stability will differ somewhat depending on the printed circuit board layout actually used.
C9
· 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-µF 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.
R5
· 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.

No. 5714-5/10
 LA4906

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.
D1
· 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.
L1
· 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 self-
excitation 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.

Standby function Pin 21 IC Internal Equivalent Circuit

500 µA or less About 1.4 V (2VBE)

· 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 µA. Use the following
formula to determine the value of R1 that meets this condition.
Applied standby
applied voltage – 1.4 V voltage
R1 = – 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 Beep signal
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 VCC voltage 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.

No. 5714-6/10
 LA4906

Quiescent current, ICCO – mA

Output power, PO – W
Both
Overvoltage channels
protection circuit

Output pin voltage, VN – V

operating
operation

Supply voltage, VCC –V Input level, VIN – mV rms

ed
ed

ed
ed

ce
Both Both
ce

ex
Output power, PO – W
Output power, PO – W

ex

channels channels

ak
ak

operating operating

pe
pe

IO
IO

Supply voltage, VCC –V Supply voltage, VCC –V

Total harmonic distortion, THD – %

Total harmonic distortion, THD – %

Both Both
channels channels
operating operating

Output power, PO – W Output power, PO – W

Total harmonic distortion, THD – %

Both
Response – dB

channels
operating

Input frequency, f – Hz Input frequency, f – Hz

No. 5714-7/10
 LA4906

Channel separation, CHsep – dB

Both
channels
Output power, PO – W

operating

Input frequency, f – Hz Input frequency, f – Hz

Output noise voltage, VNO – mV rms

Ripple rejection ratio, SVRR – dB

Using a 1-µF
power-supply
capacitor

Input resistance, Rg – Ω Supply voltage, VCC –V

Ripple rejection ratio, SVRR – dB
Ripple rejection ratio, SVRR – dB

Using a 1-µF Using a 1-µF power-supply

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

Ripple frequency, fR – Hz Power supply ripple current voltage, VCCR – Vrms

Power dissipation, Pd – W

Both Both
channels
Current drain, ICC – A

channels
operating operating
f
el
its
IC
he
rt
fo

Pd for the external

Pd

transistor

Output power, PO – W Output power, PO – W

No. 5714-8/10
 LA4906

Power dissipation, Pd – W
Both Both

f
Power dissipation, Pd – W

el
its
channels channels

elf

IC
operating operating

its

he
C

rt
I

fo
he

Pd
t
or
f
Pd Pd for the
Pd for the external
external transistor
transistor

Output power, PO – W Output power, PO – W

Regulator oscillator frequency, fOSC – kHz

(Tokin Co., Ltd.)

Quiescent current, ICCO – mA

(OS capacitor)
In the recommended circuit

Supply voltage, VCC – V Ambient temperature, Ta – °C

Total harmonic distortion, THD – %

Both
Output power, PO – W

channels
operating Both
channels
operating

Ambient temperature, Ta – °C Ambient temperature, Ta – °C

With VST applied to pin 21 through a

Output pin voltage, VN – V

With VST applied to the standby pin 10-kΩ resistor)

(pin 21) through a 10-kΩ resistor · The time until the amplifier turns on
after VST is applied

Applied standby pin voltage, VST – V

No. 5714-9/10
 LA4906

■ 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 July, 1997. Specifications and information herein are subject to change
without notice.

No. 5714-10/10