TS4961T datasheet(37/49 Pages) STMICROELECTRONICS

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TS4961T

Application component information

37/49

4.2

Low frequency response

If a low frequency bandwidth limitation is required, it is possible to use input coupling

capacitors.

In the low frequency region, Cin (input coupling capacitor) starts to have an effect. Cin forms,

with Rin, a first order high-pass filter with a -3 dB cut-off frequency:

Therefore, for a desired cut-off frequency FCL, Cin is calculated as follows:

with Rin in Ω and FCL in Hz.

4.3

Decoupling of the circuit

A power supply capacitor, referred to as CS, is necessary to correctly bypass the class D

part of the TS4961T.

The TS4961T has a typical switching frequency at 250 kHz and an output fall and rise time

at approximately 5 ns. Because of these very fast transients, careful decoupling is

mandatory.

A 1 µF ceramic capacitor is enough, but it must be located very close to the TS4961T in

order to avoid any extra parasitic inductance created by a long track wire. In relation with

dI/dt, this parasitic inductance introduces an overvoltage that decreases the global

efficiency and, if it is too high, may cause a breakdown of the device.

In addition, even if a ceramic capacitor has an adequate high frequency ESR value, its

current capability is also important. A 0603 size is a good compromise, particularly when a

Ω load is used.

Another important parameter is the rated voltage of the capacitor. A 1 µF/6.3 V capacitor

used at 5 V, loses about 50% of its value. In fact, with a 5 V power supply voltage, the

decoupling value is about 0.5 µF instead of 1 µF. Since CS has a particular influence on the

THD+N in the medium-high frequency region, this capacitor variation becomes decisive. In

addition, less decoupling means higher overshoots, which can be problematic if they reach

the power supply AMR value (6 V).

4.4

Wake-up time (tWU)

There is a wait of approximately 5 ms when standby is released to set the device ON. The

TS4961T has an internal digital delay that mutes the outputs and releases them after this

time in order to avoid any pop noise.

π R

--------------------------------------

(Hz)

π R

----------------------------------------

(F)

Obsolete

Product(s)

- Obsolete

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