MSA180 查看數據表（PDF） - Oki Electric Industry

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MSA180

Piezo Speaker Amplifier

Oki Electric Industry 

¡ Semiconductor

MSA180

Supplemental Information When Using a Voice Signal on the MODE1 Pin

When using the voice signal on MODE1, as in the circuit below, care must be taken regarding the

voice input level. Application of the voice signal below VIH1level to the MODE1 pin causes the

MSA180 to switch into standby mode, interrupting the voice reproduction flow, and causing

undesired noises.

VDD

Signal

BASE

VCC

PIEZO SPEAKER

R1

MODE2

SP

C1 AIN MSA180

MODE1

SP

GND

When using a voice signal lower than VIH, refer to the circuit below. With a low-pass filter consisting

of R2 and C2, voice levels lower than VIH1 are passed through. However, select values for R2 and C2

such that the input voltage on MODE1 is greater than VIH2.

VDD

Signal

BASE

VCC

PIEZO SPEAKER

R2

R1

MODE2

SP

C1 AIN MSA180

MODE1

SP

C2

GND

The cutoff frequency of the low-pass filter is calculated as follows:

fC =

1

2p ¥ R2 ¥ C2

[Hz]

For instance, if the cutoff frequency is 50 Hz, C2 is 0.1 mF and R2 is 30 kW. For a lower cutoff frequen-

cy, use a larger value for C2 or R2.

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