Cb has an influence on the THD+N in the low frequency range. Its value is critical on the PSRR with grounded

inputs in the lower frequencies:

•

If Cb is lower than 1 µF, the THD+N improves and the PSRR worsens

•

If Cb is higher than 1 µF, the benefit on the THD+N and PSRR is small

Note:

The input capacitor Cin also has a significant effect on the PSRR at lower frequencies. The lower the value of

Cin, the higher the PSRR.

5.7

Decoupling of the circuit

Two capacitors are needed to properly bypass the TS488, a power supply capacitor Cs and a bias voltage bypass

capacitor Cb.

Cs has a strong influence on the THD+N in the high frequency range (above 7 kHz) and indirectly on the power

supply disturbances. With 1 µF, you can expect THD+N performance to be similar to the one shown in the

datasheet. If Cs is lower than 1 µF, the THD+N increases in the higher frequencies and disturbances on the power

supply rail are less filtered. On the contrary, if Cs is higher than 1 µF, the disturbances on the power supply rail are

more filtered.

Cb has an influence on the THD+N in the low frequency range. Its value is critical on the PSRR with grounded

inputs in the lower frequencies:

•

If Cb is lower than 1 µF, the THD+N improves and the PSRR worsens

•

If Cb is higher than 1 µF, the benefit on the THD+N and PSRR is small

Note:

The input capacitor Cin also has a significant effect on the PSRR at lower frequencies. The lower the value of

Cin, the higher the PSRR.

5.8

Standby mode

When the standby mode is activated an internal circuit of the TS488 is charged (see Figure 78. Internal equivalent

schematic of the TS488 in standby mode). A time required to change the internal circuit is a few microseconds

Figure 78. Internal equivalent schematic of the TS488 in standby mode

25K

25K

600K

600K

Vin1

BYPASS

Vin2

Vout1

Vout2

GND

TS488

5.9

Wake-up time

When the standby is released to put the device ON, the bypass capacitor Cb is charged immediately. As Cb is

directly linked to the bias of the amplifier, the bias does not work properly until the Cb voltage is correct. The time

to reach this voltage plus a time delay of 20 ms (pop precaution) is called the wake-up time or tWU; it is specified

in the electrical characteristics table with Cb = 1 µF.

TS488

Decoupling of the circuit

DS4579 - Rev 8

page 23/32