la4809m Sanyo Semiconductor Corporation, la4809m Datasheet - Page 7

• Manufacturer Part Number: la4809m
• Description: Monolithic Linear Ic Stereo Headphone Amplifier
• Manufacturer: Sanyo Semiconductor Corporation

7. Selection of the maximum output power value (handling of Pin 10)
8. Change of the maximum output power value (by handling Pin 2)
9. Standby pin (Pin 3)
This IC enables selection of two types of maximum output power value according to the handling method of Pin 10.
The regulator circuit for output power control is built in, in which, by changing the voltage of Pin 2, the regulator
voltage : Vreg is changed to enable selection of the maximum output power value.
When the maximum output power value is to be changed under CPU
control, use the NPN transistor as shown in Fig.4, so that the Pin 10
voltage approaches the GND potential (0.1V or below) sufficiently.
Pin 2 voltage : V2 is determined from the constant-current source and internal resistance as shown in Fig.5.
The internal regulator voltage and amplifier operating reference voltage are generated from this Pin 2 voltage.
Accordingly, to change the maximum output power value, connect the resistance : Rrf between Pin 2 and GND as
shown in Fig.5. This will cause change in the Pin 2 voltage. Note that, in view of circuit operation, the Pin 2 voltage
must be set to 1.6V or above.
If the discharge constant is not to be changed, Use the NPN transistor to control the Rrf connection as shown in Fig.6.
By controlling the standby pin, the mode can be changed over between standby and operation. Though this control is
possible directly by the CPU output port, the control may be exposed to adverse affect of digital noise from CPU. It is
recommended therefore to insert series resistance (1kΩ or more).
Rrf
Mode-A (P O max = 55mW) : Pin 10 set to the OPEN state
Mode-B (P O max = 160mW) : Pin 10 connected to the GND line
Operating ⇒ Mode-A : 54kΩ used
Not operating (at a time of falling) ⇒ 157kΩ (54kΩ + 26kΩ + 77kΩ) used
Regulator voltage : Vreg = V2 × 2
Amplifier operating reference voltage : Vref = V2 × 1
Standby mode ⇒ V3 = 0V to 0.6V
Operation mode ⇒ V3 = 2V to 9V (for V CC = 9V or above), V3 = 2V to V CC (for V CC = less than 9V)
Crf
RF
Pin 2 voltage : V2 = 2.1V,
Internal regulator voltage : Vreg = 4.2V,
Amplifier operating reference voltage : Vref = 2.1V
Pin 2 voltage : V2 = 3.1V,
Internal regulator voltage : Vreg = 6.2V,
Amplifier operation reference voltage : Vref = 3.1V
2
PLS-cnt
Mode-B : 80kΩ (54kΩ + 26kΩ) used
54kΩ
39μA
Fig.5
V CC
26kΩ
77kΩ
STBY-cnt
LA4809M
from CPU
from CPU
Fig.6
Rrf
Crf
PLS
2
3
Fig.4
Continued on next page.
RF
STBY
10
V CC
10kΩ
22μA
No.A1569-7/15