TFA9842AJ_1 © Koninklijke Philips Electronics N.V. 2006. All rights reserved.
Preliminary specification Rev. 01 — 28 April 2006 12 of 18
Philips Semiconductors
TFA9842AJ
7.5 W stereo power amplifier with volume control
13.2.2 Power supply decoupling
Proper supply bypassing is critical for low-noise performance and high supply voltage
ripple rejection. The respective capacitor location should be as close as possible to the
device and grounded to the power ground. Proper power supply decoupling also prevents
oscillations.
For suppressing higher frequency transients (spikes) on the supply line a capacitor with
low ESR, typical 100 nF, has to be placed as close as possible to the device. For
suppressing lower frequency noise and ripple signals, a large electrolytic capacitor, e.g.
1000 µF or greater, must be placed close to the device.
The bypass capacitor connected to pin SVR reduces the noise and ripple on the mid rail
voltage. For good THD and noise performance a low ESR capacitor is recommended.
13.3 Thermal behavior and heatsink calculation
The measured maximum thermal resistance of the IC package, R
th(j-mb)
, is 2.0 K/W.
A calculation for the heatsink can be made, with the following parameters:
T
amb(max)
=60°C (example)
V
CC
= 17 V and R
L
=4Ω (SE)
T
j(max)
= 150 °C (specification)
R
th(tot)
is the total thermal resistance between the junction and the ambient including the
heatsink. This can be calculated using the maximum temperature increase divided by the
power dissipation:
Fig 15. Printed-circuit board layout (single-sided); components view
AUDIO POWER CS NIJMEGEN
27 Jan. 2003 / FP
IN2+ IN1+
MUTE
SB ON
TVA
−SE2+
−SE1+
+V
P
1000 µF
1000 µF
1000 µF
BTL1/2
1
22
µF
10 kΩ
10
kΩ
001aaa426
100 nF
150 µF
220
nF
220
nF
MODE
SGND
SVR
SVR
CIV
CIV
