TDA8920B_2
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Product data sheet
Rev. 02 — 07 November 2005
16 of 34
Philips Semiconductors
TDA8920B
2
×
100 W class-D power amplifier
13.2 MODE pin
For pop noise-free start-up an RC time-constant must be applied on the MODE pin. The
bias-current setting of the VI-converter input is directly related to the voltage on the MODE
pin. In turn the bias-current setting of the VI converters is directly related to the DC output
offset voltage. Thus a slow dV/dt on the MODE pin results in a slow dV/dt for the DC
output offset voltage, resulting in pop noise-free start-up. A time-constant of 500 ms is
sufficient to guarantee pop noise-free start-up (see also
and
13.3 Output power estimation
The achievable output powers in several applications (SE and BTL) can be estimated
using the following expressions:
SE:
(1)
Maximum current (internally limited to 8 A):
(2)
BTL:
(3)
Maximum current (internally limited to 8 A):
(4)
Variables:
R
L
= load impedance
f
osc
= oscillator frequency
t
min
= minimum pulse width (typically 150 ns)
V
P
= single-sided supply voltage (so, if supply is
±
30 V symmetrical, then V
P
= 30 V)
P
o(1%)
= output power just at clipping
P
o(10%)
= output power at THD = 10 %
P
o(10%)
= 1.24
×
P
o(1%)
.
13.4 External clock
When using an external clock the following accuracy of the duty cycle of the external clock
has to be taken into account: 47.5 % <
δ
< 52.5 %.
P
o 1%
(
)
R
L
R
L
0.4
+
--------------------
V
P
1
t
min
f
osc
×
–
(
)
×
×
2
2
R
L
×
-----------------------------------------------------------------------------------------
=
I
o peak
(
)
V
P
1
t
min
f
osc
×
–
(
)
×
R
L
0.4
+
------------------------------------------------------
=
P
o 1%
(
)
R
L
R
L
0.8
+
--------------------
2V
P
1
t
min
f
osc
×
–
(
)
×
×
2
2
R
L
×
---------------------------------------------------------------------------------------------
=
I
o peak
(
)
2V
P
1
t
min
f
osc
×
–
(
)
×
R
L
0.8
+
---------------------------------------------------------
=
