TS4962_10 Datasheet, PDF (32/44 Pages) STMicroelectronics – 2.8 W filter-free mono class D audio power amplifier

Application information
TS4962
4.5
Decoupling of the circuit
A power supply capacitor, referred to as C_S, is needed to correctly bypass the TS4962.
The TS4962 has a typical switching frequency at 250 kHz and output fall and rise time about
5 ns. Due to these very fast transients, careful decoupling is mandatory.
A 1 µF ceramic capacitor is enough, but it must be located very close to the TS4962 in order
to avoid any extra parasitic inductance being created by an overly 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
4 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. As C_S has 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).
4.6
Wake-up time (t_WU)
When the standby is released to set the device ON, there is a wait of about 5 ms. The
TS4962 has an internal digital delay that mutes the outputs and releases them after this
time in order to avoid any pop noise.
4.7
Shutdown time (t_STBY)
When the standby command is set, the time required to put the two output stages into high
impedance and to put the internal circuitry in standby mode is about 5 ms. This time is used
to decrease the gain and avoid any pop noise during the shutdown phase.
4.8
Consumption in standby mode
Between the standby pin and GND there is an internal 300 kΩ resistor. This resistor forces
the TS4962 to be in standby mode when the standby input pin is left floating.
However, this resistor also introduces additional power consumption if the standby pin
voltage is not 0 V.
For example, with a 0.4 V standby voltage pin, Table 3 on page 4 shows that you must add
0.4 V/300 kΩ = 1.3 µA typical (0.4 V/273 kΩ = 1.46 µA maximum) to the standby current
specified in Table 5 on page 5.
32/44
Doc ID 10968 Rev 8