LA4809M 查看數據表（PDF） - SANYO -> Panasonic

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LA4809M

Stereo Headphone Amplifier

SANYO -> Panasonic 

Cautions for use

LA4809M

1. Input coupling capacitors (Cin1, Cin2)

Cin1 (Cin2) is an input coupling capacitor, which is intended for DC cut. This capacitor forms a high pass filter

together with the internal resistance of 45kΩ attenuating the bass frequency signal. Set the capacitance value with due

consideration of the cut-off frequency.

Note that the cut-off frequency is expressed as follows :

1ch ⇒ fc1 = 1/ (2π × Cin1 × 45000)

2ch ⇒ fc2 = 1/ (2π × Cin2 × 45000)

This capacitor also affects the pop noise at a time of falling. Note that setting the higher capacitance value causes delay

of the capacitor discharge rate, causing louder pop noise.

2. Output coupling capacitors (Cout1, Cout2)

Cout1 (Cout2) is an output coupling capacitor, which is intended for DC cut. This capacitor forms a high pass filter

together with the load impedance of RL, attenuating the bass frequency signal. Set the capacitance value with due

consideration of the cut-off frequency. Normally, the chemical capacitor is used. When setting the capacitance value,

take into account the characteristics of the chemical capacitor, namely, the capacitance value of chemical capacitor

tends to decrease at low temperature.

Note that the cut-off frequency is expressed as follows :

1ch ⇒ fc3 = 1/ (2π × Cout1 × RL)

2ch ⇒ fc4 = 1/ (2π × Cout2 × RL)

This capacitor also affects the pop noise at a time of rising. Note that setting the higher capacitance value causes louder

pop noise.

3. Power supply line capacitor (CVCC)

CVCC is intended to stabilize the power supply line. Arrange this capacitor as near to IC as possible and always use the

ceramic capacitor with superior high frequency characteristics.

Increase the capacitance value when the power supply line is relatively unstable.

4. Pin 2 capacitor (Crf)

Crf is a capacitor to determine the transient response characteristics of the Pin 2 voltage (reference voltage) : Vrf. At a

time of rising, this is charged by the internal constant-current source (about 39μA). At a time of falling, this is

discharged by the internal resistance (about 157kΩ). Due attention must be paid because pop noise and the amplifier

rise / fall time change depending on the transient response characteristics of Pin 2 voltage. Decreasing the capacitance

value to shorten the response time, pop noise becomes louder. Therefore, the use of the value shown below as the

capacitance value is recommended. As this capacitor reduces the power supply ripple component, decrease in the

capacitance value results in lowering of the ripple removal ratio.

Crf recommended values : 1μF to 3.3μF

5. Voltage gain

The voltage gain of amplifier is determined by the internal resistance and is fixed at about 11.7dB. When the output

level is to be changed, attempt attenuation with the resistor in the forward stage of input as shown in Fig.1. To enhance

the degree of attenuation, use two resistors as shown in Fig.2 so as to reduce internal-resistor variation factors.

Though attenuation in the backward stage of output as shown in Fig.3 is possible, this may cause decrease in the

maximum output power.

OUT

other IC

IN

LA4809M

(Low attenuation degree)

Fig.1

OUT

other IC

IN

LA4809M

(High attenuation degree)

Fig.2

OUT

+

LA4809M

Fig.3

6. Load capacitance

When connecting a capacitor between the output pin and GND for an anti-electric wave radiation measure, this

capacitor may cause decrease in the phase margin of power amplifier, resulting in the oscillation phenomenon. When

connecting this capacitor, pay attention to its capacitance value.

Recommended capacitance value : 560pF or less, or 0.01μF to 0.1μF

No.A1569-6/15

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