la4815m Sanyo Semiconductor Corporation, la4815m Datasheet - Page 9

• Manufacturer Part Number: la4815m
• Description: Monaural Power Amplifier
• Manufacturer: Sanyo Semiconductor Corporation

10. Signal mixing methods
11. Short-circuit between pins
12. Load short circuit
13. Maximum ratings
The following methods can be used to mix a beep, key tone or other signal into the audio signal. Note that when input
to Pin 8 is selected, amplification of signals input from Pin 3 changes according to impedance Z8 connected to Pin 8.
10-1. Mixing method using resistors in the Pin 3 input front end
10-2. Method using input to Pin 8
Turning on the power supply with some pins short-circuited may cause deterioration or breakdown. Therefore, when
mounting the IC on a board, check to make sure that no short-circuit is formed between pins by solder or other foreign
substances before turning on the power supply.
Leaving the IC for a long time in the condition with a load short circuit may cause deterioration or breakdown.
Therefore, never short-circuit the load.
When used under conditions near the maximum ratings, even a slight fluctuation in the conditions may cause the
maximum ratings to be exceeded, possibly resulting in a breakdown or other accidents. Therefore, always provide
enough margin for fluctuations in the supply voltage and other conditions, and use within a range not exceeding the
maximum ratings.
• First signal system (Signal-1) voltage gain : Vg1
• Second signal system (Signal-2) voltage gain : Vg2
Vg1 = 20log (Vout/Vin1) = 20log (4 × (125 + Z8) (500 + (125 × Z8/(125 + Z8)))/(25 × Z8))
Vg2 = 20log (Vout/Vin2) = 20log (10000/(125 + R1))
Signal-2
Signal-1
Signal-2
Signal-1
other IC
* Z8 = R1 + ro
* fc2 = 1/(2π × Cin2 × (R1 + 125))
other IC
ro
ro
ro
ro
OUT2
OUT1
OUT2
OUT1
Vout2
Vout1
Vin2
Rg2
+
Cin2
Rg1
LA4815M
Vin1
Figure 10
Figure 11
Rg3
Rg2
R1
Cin
8
3
GAIN2
IN
Pin 3 input impedance : Zin = 100kΩ
Rg1
LA4815M
Vin
Cin
Pre-Amp
100kΩ
125Ω
500Ω
+
-
3
Vbias
IN
PWR - Amp
10kΩ
LA4815M
+
-
100kΩ
+
-
OUT
Pre-Amp
Vbias
5 Vout
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