SA58670A_2
© NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 02 — 23 October 2008
16 of 24
NXP Semiconductors
SA58670A
2.1 W/channel stereo class-D audio amplifier
11. Application information
11.1 Power supply decoupling considerations
The SA58670A is a stereo class-D audio amplifier that requires proper supply voltage
decoupling to ensure the rated performance for THD+N and power efficiency. To decouple
high frequency transients, supply voltage spikes and digital noise on the supply voltage
bus line, a low Equivalent Series Resistance (ESR) capacitor of typically 1
µ
F is placed as
close as possible to the PVDD pins of the SA58670A. It is important to place the
decoupling capacitor at the supply voltage pins of the SA58670A because any resistance
or inductance in the PCB trace between the SA58670A and the capacitor can cause a
loss in efficiency. Additional decoupling using a larger capacitor, 4.7
µ
F or greater, may be
done on the supply voltage connection on the PCB to filter low frequency signals. Usually
this is not required due to high PSRR of the SA58670A.
11.2 Input capacitor selection
The SA58670A does not require input coupling capacitors when used with a differential
audio source that is biased from 0.5 V to V
DD
−
0.8 V. In other words, the input signal must
be biased within the common-mode input voltage (V
i(cm)
) range. If high-pass filtering is
required or if it is driven using a single-ended source, input coupling capacitors are
required.
The 3 dB cut-off frequency created by the input coupling capacitor and the input resistors
(see
) is calculated by
(1)
Fig 16. SA58670A application schematic
002aad665
SA58670A
OUTRP
OUTRN
10
µ
F
1 nF
1 nF
FB
FB
1 nF
1 nF
OUTLP
OUTLN
V
DD
G1
V
DD
PVDD
PGND
1
µ
F
V
DD
10
µ
F
1
µ
F
V
DD
SDL
SDR
AVDD
10
µ
F
1
µ
F
PGND
V
DD
PVDD
G0
INLP
1
µ
F
INLN
1
µ
F
differential inputs
left channel
INRN
1
µ
F
INRP
1
µ
F
differential inputs
right channel
AGND
FB
FB
f
3dB
–
1
2
π
R
i
×
C
i
×
------------------------------
=
