TB2905HQ Просмотр технического описания (PDF) - Toshiba

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TB2905HQ

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

Toshiba 

Operational Description (Each description applies to a single channel)

TB2905HQ

1. Voltage Gain

The TB2905HQ has no NF (negative feedback) pins. Therefore, the voltage gain (GV) is determined

within the IC.

Input

Amplifier 1

Amplifier 2A

Amplifier 2B

Figure 1 Amplifier Configuration

Voltage gain of amplifier 1: GV1 = 0 dB

Voltage gain of amplifiers 2A and 2B: GV2 = 20 dB

Voltage gain obtained by BTL connection: GV (BTL) = 6 dB

Therefore, the total voltage gain is determined by the following expression:

GV = GV1 + GV2 + GV (BTL) = 0 + 20 + 6 = 26dB

Although this configuration without an NF pin does not allow the user to adjust voltage gain, it

eliminates the need for an NF capacitor, resulting in lower total application cost and smaller mounting

space.

2. Standby Switching Function (Pin 4)

The TB2905HQ can be powered up or

down by controlling the state of pin 4

(standby pin).

The threshold voltage for pin 4 is

approximately 3 VBE (typ.). The supply

current in standby state is approximately 2

µA (typ.).

ON Power

OFF

10 kΩ

4

VCC

≈ 2 VBE

To bias

cutoff circuit

Pin 4 control voltage: VSB

Stand-by

ON

OFF

Power

OFF

ON

VSB (V)

0~0.5

2.5~6 V

Figure 2 Driving pin 4 high powers up

the TB2905HQ

When changing the time constant for pin 4, check the pop noise produced.

< Advantages of standby switching >

(1) The microcontroller can directly turn VCC on or off without using a switching relay.

(2) Since the control current is microscopic, a switching relay with small current capacity is satisfactory

for switching.

3

2005-08-17

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