TB2905HQ

2005-08-17

6

5.

Pin 25 has open-collector output (active low) structure, as shown in Figure 7.

If the output waveform is clipped, the clipping detection circuit in the IC activates and turns the Q1 NPN

transistor on.

The microcontroller can use this signal to control the volume and tone control circuits, thus improving

sound quality.

Pin 25 should be left open when this function is not used.

Pin 25: Open-collector output (active low)

Output clipping

detector

25

Q1

5 V

L.P.F.

smoothing

circuit

Volume control circuit

Tone control circuit

(Example application)

DC

DC

AC

t

t

t

(C)

(A)

(B)

(A) Output AC waveform

(B) Clipping detection circuit

(C) Clipping detection pin

(output of pin 25)

Clipped level

Clipped level

Figure 8

Clipping detection mechanism

5V

GND