TB2905HQ データシートの表示（PDF） - Toshiba

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TB2905HQ

Class KB High-Efficiency, Low-Frequency Power Amplifier IC Maximum Power: 47 W × 4 Channels

Toshiba 

Large-current capacity switch

Battery

VCC

VCC

- Conventional method -

TB2905HQ

Relay

Battery

From microcontroller

Small-current capacity switch

Battery

From microcontroller

Stand-By VCC

Stand-By VCC

- Standby switching -

Battery

Figure 3 Standby switching

3. Muting Function (Pin 22)

Driving pin 22 low triggers audio muting.

The time constant for muting is determined from R1 and C4. Select the constants considering the pop noise

that is produced when powering the TB2905HQ on/off or turning muting on/off. (See Figures 4 and 5.)

Pin 22 is designed to be controlled at 3.3 V.

The pin functions as a current source switch for the internal muting circuit and is designed so that its

discharging current is 200 µA. The value of the external pull-up resistor is based on this current.

Example: When changing the control voltage from 3.3 V to 5 V, 5 V/3.3 V x 47 kΩ = 71 kΩ

The TB2905HQ internally triggers muting when the voltage is dropped, taking in a current of 200 µA. It

cannot take in the current if the pull-up resistance is too low. The series resistance (R1) for pin 22 must,

therefore, be at least 47 kΩ.

3.3Ｖ

22

R1

C4

1 kΩ

Muting

ON/OFF control

20

Vcc = 13.2 V

0 f = 1kHz

RL = 4 Ω

VOUT = 20dBm

−20

ATT – VMUTE

−40

−60

−80

−100

−120

0

0.5

1

1.5

2

2.5

3

Muting pin voltage: VMUTE (V)

Figure 4 Muting function

Figure 5 Muting attenuation − VMUTE (V)

4

2005-08-17

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