BD7830NUV Rohm, BD7830NUV Datasheet - Page 10

• Manufacturer Part Number: BD7830NUV
• Description: 1.1W to1.5W Monaural Speaker Amplifier
• Manufacturer: Rohm

●Selection of external components
●Use when VCC = STBY short
BD7830NUV
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www.rohm.com
①Setting gain from desired output
②Setting input resistance and feedback resistance from gain
③Setting input coupling capacitor from low-range cut-off frequency
④Setting bias capacitor and SOFT capacitor to minimize pops
Since this IC is designed on the assumption that it will be used to switch standby mode ON and OFF while the power supply
remains ON, normally STBY should be switched from H to L and the SOFT voltage should be discharged before powering
down. When used while VCC = STBY short, pop sounds may occur if the IC's power supply is reduced prior to discharging
the SOFT voltage.
To prevent pop sounds, you must ① set STBY = H→L before setting VCC = H→L, and ② forcibly discharge the SOFT
voltage.
A sample circuit in which VCC = STBY short is used is shown below.
・Sample circuit configuration when VCC = STBY short
②
Fast discharge of
SOFT voltage at
power-off
Output Po is determined via the following formula, from which the required gain Av can also be obtained.
Gain Av is determined via the following formula, from which input resistance Rin and feedback resistance Rf can be set.
Rin is set with the input side's drive capacity taken into account.
Low-range cut-off frequency fc is determined via the following formula, from which input coupling capacitor Cin can be set.
It is recommended that the capacitance of the bias capacitor CB be set to at least 10 times that of the input coupling
capacitor Cin, in order to soften the rise of the bias voltage while improving the Cin following ability.
Also, when a higher gain is used, the capacitance of the SOFT capacitor Cs can be raised to control pop sounds.
Po [W] = Vo
Vo = Av ・ Vin
Av ≧
Av = (Rf / Rin) ・ 2
fc [Hz] = 1 / (2π ・ Rin ・ Cin)
Cin ≧ 1 / (2π ・ Rin ・ fc)
Av = 2 (6 dB at BTL)
Av = 4 (12 dB at BTL)
Av = 8 (18 dB at BTL)
Av = 20 (26 dB at BTL) → Cs ・ (80 / fc) ≧ 0.068 µF
Po
・
2
RL
[Vrms] / RL [Ω]
/ Vin
Cin
Rin
1μ
C
→ Cs ・ (80 / fc) ≧ 0.01 µF
→ Cs ・ (80 / fc) ≧ 0.022 µF
→ Cs ・ (80 / fc) ≧ 0.033 µF
S
STBY
BIAS
SOFT
IN－
1
2
3
4
SOFT
Bias
2nd Amp
1st Amp
Rf
10/17
OUT2
GND
VCC
OUT1
8
7
6
5
C
D
Slow power-off of IC itself
VCC
①
STBY = H → L at
power-off
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Technical Note
2010.06 - Rev.A