NXP Semiconductors TDA8932B - Manual (Page 26)

TDA8932B_4 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 04 — 18 December 2008 26 of 48
NXP Semiconductors
TDA8932B
Class-D audio amplifier
(9)
Where:
R
EQ
= equivalent resistance (
Ω
)
R3 = parallel resistor (
Ω
)
Z
i
= internal input impedance (
Ω
)
Example:
Substituting R1 = R2 = 4.7 k
Ω
, Z
i
= 100 k
Ω
and R3 = 22 k
Ω
in Equation 8 and Equation 9
results in a gain of G
v(tot)
= 26.3 dB.
14.6 Device synchronization
If two or more TDA8932B devices are used in one application it is recommended that all
devices are synchronized running at the same switching frequency to avoid beat tones.
Synchronization can be realized by connecting all OSCIO pins together and configuring
one of the TDA8932B devices as master, while the other TDA8932B devices are
configured as slaves (see
Figure 11 ).
A device is configured as master when connecting a resistor between pins OSCREF and
V
SSD(HW)
setting the carrier frequency. Pin OSCIO of the master is then configured as an
oscillator output for synchronization. The OSCREF pins of the slave devices should be
shorted to V
SSD(HW)
configuring pin OSCIO as an input.
14.7 Thermal behavior (printed-circuit board considerations)
The TDA8932B is available in two different thermally enhanced packages:
TDA8932BT in a SO32 (SOT287-1) package for reflow and wave solder process
TDA8932BTW in an HTSSOP32 (SOT549-1) package for reflow solder process only
The SO32 package has special thermal corner-leads, increasing the power capability
(reducing the overall R
th(j-a)
. To benefit from the corner leads pins V
SSD(HW)
(pins 1, 16, 17
and 32) should be attached to a copper plane. The SO32 package is very suitable for
applications with limited space for a thermal plane (in a single layer PCB design).
R
EQ
R3 Z
i
×
R3 Z
i
+
------------------ =
Fig 11. Master slave concept in two chip application
001aaf600
39 k Ω
Rosc
100 nF
Cosc
IC1
TDA8932B
OSCREF V
SSD(HW)
V
SSD(HW)
OSCIO
IC2
TDA8932B
master slave
OSCIO OSCREF