lv49821vh Sanyo Semiconductor Corporation, lv49821vh Datasheet - Page 7

• Manufacturer Part Number: lv49821vh
• Description: Bi-cmos Ic For Portable Electronic Device Use 1.4w ? 2ch Btl Power Amplifier
• Manufacturer: Sanyo Semiconductor Corporation

Usage Note
1. Input coupling capacitor (C1 and C2)
2. BTL voltage gain
3. Beep signal input pin (pin 3)
4. pin 4 capacitor (C3)
5. Power supply line capacitor (C7and C8)
C1 and C2 are input coupling capacitors that are used to cut the DC component. The input coupling capacitors C1, C2
and the input resistors R1 and R3 make up the high-pass filter, attenuating the bass frequency. Therefore, the
capacitance value must be selected with due consideration of the cut-off frequency.
The cut-off frequencies are expressed by the following formulas.
This capacitor affects the pop sound at startup. Note with care that increasing the capacitance value lengthens the
charging time of the capacitor, which will make the pop sound louder.
The voltage gain of the first amplifier is determined by the ratio between the resistors R1 and R2 (R3 and R4).
Therefore, the BTL voltage gain is expressed by the following formulas.
The BTL voltage gain must be set in the range of 0 to 26 dB.
This pin is connected to the non-inverting input block of the first amplifier of the BTL amplifier, and is biased
internally by a 50kΩ resistor. The input coupling capacitor C4 and the bias resistor make up a high-pass filter that
attenuates bass band signals, so when determining the C4 capacitance value, the value must be set with due
consideration of the cut-off frequency. The cut-off frequency is expressed by the following formula.
In addition, when input from Pin 3, the BTL voltage gain is expressed by the following formulas.
When setting the signal level, the signal should be attenuated and input as shown in Fig.1.
When not using this input pin, connect it to pin 4 as shown in Application Circuit Example-2.
This capacitor is a ripple filter capacitor. The internal resistors (100kΩ + 450kΩ) and C3 make up a low-pass filter that
is used to reduce the power supply ripple component and increase the ripple rejection ratio.
Note that inside the IC, the rising-transient-response-characteristic of the pin 4 voltage (reference voltage) is used to
activate the automatic pop sound reduction circuit. Therefore, when reducing the C3 capacitance value to increase the
voltage rise speed, the design should take into account that the pop sound increases during voltage rise.
The bypass capacitor C8 is used to remove the high frequency component that cannot be eliminated by the power
supply capacitor C7 (chemical capacitor). Place the bypass capacitor C8 as near to the IC as possible, and use a
ceramic capacitor with good high frequency characteristics.
When using a stabilized power supply, these capacitors can also be combined into a single 2.2µF ceramic capacitor.
Note that when the power supply line is relatively unstable, the power supply capacitor C7 capacitance value must be
increased.
1ch ⇒ fc1 = 1/(2π × C1 × R1)
2ch ⇒ fc2 = 1/(2π × C2 × R3)
1ch ⇒ Vg1 = 20 × log(R2/R1) …unit: dB
2ch ⇒ Vg2 = 20 × log(R4/R3) … unit: dB
1ch ⇒ VgBTL1 = 6 + 20 × log(R2/R1) … unit: dB
2ch ⇒ VgBTL2 = 6 + 20 × log(R4/R3) … unit: dB
fc3 = 1/(2π× C4 × 50000)
1ch ⇒ VgBTL1 = 6 + 20 × log(1+R2/(R1 + ro)) … unit: dB
2ch ⇒ VgBTL2 = 6 + 20 × log(1+R4/(R3 + ro)) … unit: dB
other IC
Beep signal in
ro
OUT
LV49821VH
C1
Fig.1
R1
R2
C3
C4
13
1
3
4
LV49821VH
VREF
No.A1468-7/15