TS4962_07 STMICROELECTRONICS [STMicroelectronics], TS4962_07 Datasheet - Page 33

• Manufacturer Part Number: TS4962_07
• Description: 2.8W filter-free mono class D audio power amplifier
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

TS4962
4.3
4.4
Common mode feedback loop limitations
As explained previously, the common mode feedback loop allows the output DC bias voltage
to be averaged at V
However, due to V
page
range depends upon the values of V
V
with
and the result of the calculation must be in the range:
Due to the +/-9% tolerance on the 150kΩ resistor, it’s also important to check V
conditions:
If the result of V
be used (with V
For example:
With V
3V-0.8V=2.2V. With 136.5kΩ we find 1.97V and with 163.5kΩ we have 2.02V. So, no input
coupling capacitors are required.
Low frequency response
If a low frequency bandwidth limitation is requested, it is possible to use input coupling
capacitors.
In the low frequency region, C
with R
So, for a desired cut-off frequency we can calculate C
with R
icm
value, we can apply this formula (no tolerance on R
7), the common mode feedback loop can play its role only within a defined range. This
in
in
CC
, a first order high-pass filter with a -3dB cut-off frequency:
in Ω and F
=3V, R
V
---------------------------------------------------------------------------------- - V
CC
CC
icm
in
=150k and V
×
icm
2
CL
between 2.4V and 2.5V, input coupling capacitors are mandatory).
calculation is not in the previous range, input coupling capacitors must
R
CC
×
in
in Hz.
limitation in the input stage (see
(
/2 for any DC common mode bias input voltage.
R
+
in
2
V
×
+
icm
136.5kΩ
V
IC
in
=
IC
(input coupling capacitor) starts to have an effect. C
×
F
=2.5V, we typically find V
V
----------------------------------------------------------------------------- -
C
CL
CC
136.5kΩ
in
0.5V V
)
V
=
CC
=
×
IC
2
------------------------------------- -
2π
--------------------------------------- -
2π
R
×
≤
and R
=
in
(
×
×
R
+
icm
≤
In
---------------------
R
R
in
2
+
1
in
1
in
icm
+
≤
×
2
in
+
×
×
V
150kΩ
In
V
(A
CC
≤
C
IC
F
-
Vdiff
V
---------------------------------------------------------------------------------- -
CL
in
×
–
CC
(V)
0.8V
150kΩ
)
). To have a good estimation of the
in
×
Table 3: Operating conditions on
2
,
(Hz)
R
in
(F)
×
icm
):
in
(
R
+
=2V, which is lower than
in
2
×
+
(V)
163.5kΩ
V
Application information
IC
×
163.5kΩ
)
icm
in these
in
forms,
33/46