TS4990EKIJT STMICROELECTRONICS [STMicroelectronics], TS4990EKIJT Datasheet - Page 20

• Manufacturer Part Number: TS4990EKIJT
• Description: 1.2 W audio power amplifier with active low standby mode
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Application information
Note:
4.5
20/32
Therefore, the power dissipated by each amplifier is:
and the maximum value is obtained when:
and its value is:
This maximum value is only dependent on power supply voltage and load values.
The efficiency is the ratio between the output power and the power supply:
The maximum theoretical value is reached when V
Decoupling of the circuit
Two capacitors are needed to correctly bypass the TS4990: a power supply bypass
capacitor C
C
an indirect influence on power supply disturbances. With a value for C
expect THD+N levels similar to those shown in the datasheet.
In the high frequency region, if C
on the power supply rail are less filtered.
On the other hand, if C
more filtered.
C
result of PSRR (with input grounded and in the lower frequency region).
If C
If C
to PSRR is substantial.
Note that C
of C
s
b
has particular influence on the THD+N in the high frequency region (above 7 kHz) and
has an influence on THD+N at lower frequencies, but its function is critical to the final
b
b
in
P
is lower than 1 µF, THD+N increases at lower frequencies and PSRR worsens.
is higher than 1 µF, the benefit on THD+N at lower frequencies is small, but the benefit
, the higher the PSRR.
diss
= P
in
s
and a bias voltage bypass capacitor C
has a non-negligible effect on PSRR at lower frequencies. The lower the value
supply
- P
out
s
is higher than 1 µF, those disturbances on the power supply rail are
(W)
s
P
is lower than 1 µF, it increases THD+N and disturbances
diss
η =
max
P
diss
------------------ - =
P
=
P
π
---- - = 78.5%
supply
δP
----------------- - = 0
4
δP
2V
-------------- -
out
π
diss
2
=
out
R
2
CC
2 2V
---------------------- P
L
π R
---------------------- -
πV
PEAK
4V
b
.
CC
L
PEAK
CC
(W)
= V
out
CC
–
P
, so:
out
s
of 1 µF, you can
TS4990