SA58670 Datasheet, PDF (16/25 Pages) NXP Semiconductors – 2.1 W/channel stereo Class D audio amplifier

NXP Semiconductors
11. Application information
SA58670
2.1 W/channel stereo class-D audio amplifier
differential inputs
left channel
differential inputs
right channel
V_DD
1 µF
1 µF
1 µF
1 µF
INLP INLN AGND
G1
INRN INRP
G0
V_DD
FB
1 nF
FB
1 nF
OUTLP
OUTLN
FB
OUTRP
1 nF
SA58670
FB
OUTRN
1 nF
V_DD
10 µF
PVDD
1 µF
PGND
SDL
PVDD
PGND
SDR AVDD
1 µF
V_DD
10 µF
1 µF
10 µF
V_DD
Fig 16. SA58670 application schematic
001aah515
11.1 Power supply decoupling considerations
The SA58670 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 µF is placed as
close as possible to the PVDD pins of the SA58670. It is important to place the decoupling
capacitor at the supply voltage pins of the SA58670 because any resistance or inductance
in the PCB trace between the SA58670 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
supply voltage connection on the PCB to filter low frequency signals. Usually this is not
required due to high PSRR of the SA58670.
11.2 Input capacitor selection
The SA58670 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 Table 6) is calculated by Equation 1:
f _–3dB = -₂---_π-----_×-----_R1---_i---_×-----_C----_i
(1)
SA58670_1
Product data sheet
Rev. 01 — 4 January 2008
© NXP B.V. 2008. All rights reserved.
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