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LV49821VH Datasheet PDF : 15 Pages
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LV49821VH
6. Standby pin (pin 2)
By controlling the standby pin, the mode changeover can be made between standby and operation modes. Direct
control is possible using the CPU output port, but inserting a series resistor R5 (1 kΩ or more) is recommended in case
the pin is affected by digital noise from the CPU.
Standby mode … V2 = 0V to 0.3V
Operating mode…V2 = 1.6V to VCC
In addition, when not using standby mode, this pin can also be used interlocked
with the power supply as shown in Fig. 2. The series resistor R5 can be
VCC
11 VCC
2 STBY
R5
eliminated, but the current I2 expressed by the following formula flows through
the standby pin, so this should be taken into account in the design.
Pin 2 inflow current (unit: A): I2 = 7 × 10-6 + (VCC − 0.7) / (R5 + 30000)
Fig.2
7. Pin 6 control (2nd amplifier stop control function)
Pin 6 performs on/off control for the BTL amplifier’s second amplifier operation. This function enables switching
between speaker drive (BTL output system) and headphone drive (single end output system). The control comparator
is connected to this pin, and this threshold voltage is generated by resistance division from the supply voltage. For this
reason, care should be taken, as the threshold value varies according to the supply voltage. When switching using a
headphone jack switch, the connection method shown in Application Circuit Example-1 is recommended.
Comparator threshold value: Vth = VCC × 2/3
In addition, when controlling this pin with the CPU (BTL amplifier mute function), care should be taken for the
relationship between the supply voltage used by the CPU and the supply voltage used by the power amplifier IC. When
the supply voltage used by the power amplifier IC is higher, open/low format control as shown in Fig.3 and Fig.4 is
recommended. In addition, there is also a control method that uses three resistors as shown in Fig.5. The recommended
ratio between the resistance values of these three resistors is as follows.
RC1, RC2, RC3 resistance ratio … RC1 : RC2 : RC3 = 1 : 1 : 3
CPU
VCC
VSS
11
VCC
6 A2CNT
CPU
VDD
VCC
LV49821VH
VSS
11
VCC
6 A2CNT
LV49821VH
CPU
VDD
VSS
VCC
RC2
RC1
11
VCC
6 A2CNT
RC3
LV49821VH
Figure 3
Figure 4
Figure 5
8. Headphone drive
When also using the BTL amplifier’s first amplifier as the headphone amplifier, it is recommended to adjust the level
by inserting series resistors R6 and R8 to the signal line as shown in Application Circuit Example-1.
Note that this series resistor, the headphone load resistance and the output coupling capacitors C5 and C6 make up a
high-pass filter, so this should be taken into account in the design. The cut-off frequencies are expressed by the
following formulas.
1ch  fc1 = 1 / (2π × C5 × (R6 + RL))
2ch  fc2 = 1 / (2π × C6 × (R8 + RL))
9. Load capacitance
When connecting a capacitor between the output pin and ground to suppress electromagnetic radiation or other
purposes, the effects of this capacitor may cause the power amplifier phase margin to be reduced, resulting in
oscillation. When adding this capacitor, care should be taken for the capacitance value.
Recommended capacitance value: 0.033μF to 0.33μF
10. Thermal protection circuit
The IC has a built-in thermal protection circuit that can reduce the risk of breakdown or degradation when the IC
becomes abnormally hot for some reason. When the internal chip junction temperature Tj rises to approximately 170°
C, this protective circuit operates to cut off the power supply to the power amplifier block and stop signal output.
Operation recovers automatically when the chip temperature drops to approximately 130°C.
Note that this circuit cannot always prevent breakdown or degradation, so sufficient care should be taken for using the
IC. When the chip becomes abnormally hot, immediately turn off the power and determine the cause.
No.A1468-8/15
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