TFA9881_1104 PHILIPS [NXP Semiconductors], TFA9881_1104 Datasheet - Page 18

• Manufacturer Part Number: TFA9881_1104
• Description: 3.4 W PDM input class-D audio amplifier
• Manufacturer: PHILIPS [NXP Semiconductors]

NXP Semiconductors
13. Application information
TFA9881
Product data sheet
13.1.1 Immunity
13.1.2 Emissions
13.1 ElectroMagnetic Compatibility (EMC)
13.2 Supply decoupling and filtering
EMC standards define to what degree a (sub)system is susceptible to externally imposed
electromagnetic influences and to what degree a (sub)system is responsible for emitting
electromagnetic signals, when in Standby mode or Operating mode.
EMC immunity and emission values are normally measured over a frequency range from
180 kHz up to 3 GHz.
A major reason why amplifier devices pick up high frequency signals, and (after detection)
manifest these in the device's audio band, is the presence of analog circuits inside the
device or in the (sub)system.
The TFA9881 has digital inputs and digital outputs. Comparative tests on a
TFA9881-based (sub)system show that the impact of externally imposed electromagnetic
signals on the device is negligible in both Standby and Operating modes.
Since the TFA9881 is a class-D amplifier with digitally switched outputs in a BTL
configuration, it can potentially generate emissions due to the steep edges on the
amplifier outputs. External components can be used to suppress these emissions.
However, the TFA9881 features built-in slope control to suppress such emissions by
reducing the slew rate of the BTL output signals. By reducing the slew rate, the emissions
are reduced by 10 dB when compared with full-speed operation.
A ceramic decoupling capacitor of between 4.7 μF and 10 μF should be placed close to
the TFA9881 for decoupling the V
high-frequency current loop, thereby optimizing EMC performance. The TEST bump can
be used to route the V
All information provided in this document is subject to legal disclaimers.
DDP
Rev. 2 — 1 April 2011
bump connection (without using a PCB via).
DDP
supply. This minimizes the size of the
3.4 W PDM input class-D audio amplifier
TFA9881
© NXP B.V. 2011. All rights reserved.
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