TS4956 datasheet(43/51 Pages) STMICROELECTRONICS

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TS4956

Application information

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4.6

Decoupling of the circuit

Two capacitors are needed to properly bypass the TS4956 — a power supply capacitor Cs

and a bias voltage bypass capacitor Cb.

Cs has a strong influence on the THD+N at high frequencies (above 7 kHz) and indirectly on

the power supply disturbances.

With a Cs value of about 1 µF, you can expect to obtain THD+N performances similar to

those shown in the datasheet.

If Cs is lower than 1 µF, THD+N increases in high frequency and disturbances on power

supply rail are less filtered.

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

filtered.

Cb has an influence on THD+N at lower frequencies, but its value has critical impact on the

final result of PSRR with inputs grounded at lower frequencies:

●

If Cb is lower than 1 µF, THD+N increases at lower frequencies and the PSRR

worsens upwards.

●

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

frequency range is small.

The value of Cb also has an influence on startup time.

4.7

Power On Reset

When power is applied to VCC, an internal Power On Reset holds the TS4956 in a reset

state (shutdown) until the supply voltage reaches its nominal value. The Power On Reset

has a typical threshold of 1.75 V.

During this reset state the output configuration is the same as in the shutdown mode.

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