TB2929HQ

2009-01-29

7

5. Pop Noise Suppression

Since the TB2929HQ uses the AC-GND pin (pin 16) as the common input reference voltage pin for all

amplifiers, the ratio of the input capacitance (C1) to the AC-to-GND capacitance (C6) should be 1:4.

Also, if power is removed before C1 and C6 are completely charged, pop noise will be generated because of

unbalanced DC currents.

To avoid this problem, it is recommended to use a larger capacitor as C2 to increase the charging times of C1

and C6. Note, however, that C2 also affects the time required from power-on to audio output.

The pop noise generated by the muting and unmuting of the audio output varies with the time constant of

C4. A larger capacitance reduces the pop noise, but increases the time from when the mute control signal is

applied to C4 to when the mute function is enabled.

6. External Component Constants

Effects

Component

Recommended

Value

Purpose

When lower than

recommended value

When higher than

recommended value

Notes

C1

0.22

μF

To eliminate DC

Cut-off frequency is

increased.

Cut-off frequency is reduced.

Pop noise is

generated

turned on.

C2

10

μF

To reduce ripple

Powering on/off is faster.

Powering on/off is slower.

C3

0.1

μF

To provide

sufficient

oscillation margin

Reduces noise and provides sufficient oscillation margin

C4

1

μF

To reduce pop

noise

High pop noise. Duration until

mute function is turned on/off

is short.

Low pop noise. Duration until

mute function is turned on/off

is long.

C5

3900

μF

Ripple filter

Power supply humming and ripple filtering.

C6

1

μF

Common

reference voltage

for all input

Pop noise is suppressed when C1: C6

= 1:4.

Pop noise is

generated

turned on.

C7

0.22

μF

To eliminate DC

Cut-off frequency is

increased in AUX

Cut-off frequency is reduced

in AUX.