NJU7085 JRC, NJU7085 Datasheet - Page 10

• Manufacturer Part Number: NJU7085
• Description: Audio Amplifier / SSOP32
• Manufacturer: JRC

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NJU7085
2.1External parts
2.1.1 power supply bypassing capacitor
Select C1 which is enough good thermal characteristics and high frequency characteristics. The wiring pattern
2.1.2 Input coupling capacitor
The input impedance and input coupling capacitor (Ci) form a high pass filter which limits low frequency
2.1.3 Input resistance (Ri) and feedback resistance (Rf) of power amplifier.
The closed loop gain is adjusted by Ri and Rf .
It is given by the following equation.
The closed loop gain should be set from 0dB to +43dB.
2.1.4Reference voltage bypassing capacitor
Reference voltage bypassing capacitor (C2) affects PSRR (See Fig.2).
2.1.5 eala effect volume
The surround effect is able to adjust with eala effect volume (R2).
It is able to replace to fixed resister (R1+R2) if you select constant surround effect.
2.1.6 eala TC capacitor
2.1.7 PS capacitor
PS capacitor (C5) affects phase characteristics on eala Mobile mode.
In case of canceling L/R sound, it is able to compensate with using small capacitor.
2.1.8 Control terminal (D0,D1,D2) resistance
Control terminal resistances (R3, R8, R9) reduce pop noise at the time of changing mode control.
2.1.9 PSRR (Power Supply Rejection Ratio) vs. C2
Large bypassing capacitor (C2) improves PSRR shown in Fig.2.
But a large input coupling capacitor requires more charge time to reach its quiescent DC voltage.
Select C2 in consideration of PSRR and pop noise.
between C1 and IC should be shortened to prevent the generating of wiring resistance.
response. The input impedance is designed about 100k .
eala TC capacitor (C3) reduces pop noise at the time of changing the mode setting (Bypass eala,
Bypass Mobile, eala
The pop noise becomes smaller with using large capacitor.
- 10 -
Mobile).
70
60
50
40
30
20
10
1.E+01
0
Gv=20LOG(2Rf/Ri) = 6 [dB]
Fig.2 PSRR vs. Frequency
V+=3V,RL=4Ω,Ta=25
1.E+02
PSRR vs. Frequency
C2=2.2uF
Frequency[Hz]
1.E+03
C2=1uF
O
C,RIN=GND
C2=0.47uF
1.E+04
1.E+05