SA58671 Datasheet, PDF (16/24 Pages) NXP Semiconductors – 1.2 W/channel stereo class-D audio amplifier

NXP Semiconductors
11. Application information
SA58671
1.2 W/channel stereo class-D audio amplifier
differential inputs
left channel
differential inputs
right channel
1 µF
V_DD
1 µF
1 µF
1 µF
V_DD
INLP INLN AGND
G1
INRN INRP
G0
FB
1 nF
FB
1 nF
OUTLP
OUTLN
FB
OUTRP
1 nF
SA58671
FB
OUTRN
1 nF
V_DD
10 µF
PVDD
1 µF
PGND
SDL
SDR AVDD
1 µF
10 µF
V_DD
Fig 15. SA58671 application schematic
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11.1 Power supply decoupling considerations
The SA58671 is a stereo class-D audio amplifier that requires proper power supply
decoupling to ensure the rated performance for THD+N and power efficiency. To decouple
high frequency transients, power supply spikes and digital noise on the power bus line, a
low Equivalent Series Resistance (ESR) capacitor of typically 1 µF is placed as close as
possible to the PVDD pins of the device. It is important to place the decoupling capacitor
at the power pins of the device because any resistance or inductance in the PCB trace
between the device and the capacitor can cause a loss in efficiency. Additional decoupling
using a larger capacitor, 4.7 µF or greater, may be done on the power supply connection
on the PCB to filter low frequency signals. Usually this is not required due to high PSRR of
the device.
11.2 Input capacitor selection
The SA58671 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 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 Table 6) is calculated by Equation 1:
f _–3dB = -₂---_π-----_×-----_R1---_i---_×-----_C----_i
(1)
SA58671_2
Product data sheet
Rev. 02 — 24 October 2008
© NXP B.V. 2008. All rights reserved.
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