NXP Semiconductors TDA8932B 14. Application information

TDA8932B_3 © NXP B.V. 21 June 2007. All rights reserved.
Product data sheet Rev. 03— 21 June 2007 22 of 48
NXP Semiconductors TDA8932B
Class-D audio amplifier
14. Application information
14.1 Output power estimation
The output power Po at THD+N = 0.5 %, just before clipping, for the SE and BTL
configuration can be estimated using Equation 2 and Equation 3.
SE configuration:
(2)
BTL configuration:
(3)
Where:
VP= supply voltage VDDP1 − VSSP1 (V) or VDDP2 − VSSP2 (V)
RL= load impedance (Ω)
RDSon = on-resistance power switch (Ω)
Rs= series resistance output inductor (Ω)
RESR = equivalent series resistance SE capacitor (Ω)
tw(min) = minimum pulse width (s); 80 ns typical
fosc = oscillator frequency (Hz); 320 kHz typical with Rosc = 39 kΩ
The output power Po at THD+N = 10 % can be estimated by:
(4)
Figure 8 and Figure 9 show the estimated output power at THD+N = 0.5 % and
THD+N = 10 % as a function of the supply voltage for SE and BTL configurations at
different load impedances. The output power is calculated with: RDSon = 0.15 Ω (at
Tj=25°C), Rs= 0.05 Ω, RESR = 0.05 Ω and IO(ocp) = 4 A (minimum).
Po 0.5%()
RL
RLRDSon RsRESR +++
----------------------------------------------------------


1t
wmin()
–fosc ×()×VP ×2
8R
L
×
-------------------------------------------------------------------------------------------------------------------------------------------
=
Po 0.5%()
RL
RL2+RDSon Rs +()×
------------------------------------------------------


1t
wmin()
–fosc ×()×VP ×2
2R
L
×
--------------------------------------------------------------------------------------------------------------------------------------
=
Po10%()1.25 Po 0.5%() ×=