TFA9881_1104 PHILIPS [NXP Semiconductors], TFA9881_1104 Datasheet - Page 9

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

NXP Semiconductors
TFA9881
Product data sheet
Fig 7.
Dynamic Power Stage Activation
0.105 × full scale
0.035 × full scale
0.07 × full scale
8.4.5 Dynamic Power Stage Activation (DPSA)
8.4.6 Bandwidth extension
Table 10.
The TFA9881 uses DPSA to regulate current consumption in line with the level of the
incoming audio stream. This function switches off power stage sections that are not
needed, reducing current consumption.
Each of the TFA9881 H-bridge power stages is divided into eight sections. The number of
power stage sections activated depends on the level of the incoming audio stream. The
thresholds used by the DPSA to determine how many stages are switched on are given in
Table
sections on and off. The DPSA signal will rise in tandem with the rectified audio input
signal. When the rectified audio input signal falls, the DPSA decreases with a negative
exponential function, as illustrated in
The DPSA function can be switched off via silence pattern 0xE2. When DPSA is off, all
power stage sections are activated in Operating mode.
Table 11.
The TFA9881 output spectrum has a sigma-delta converter characteristic.
illustrates the output power spectrum of the TFA9881 when it is receiving a PDM input
stream without audio content and with bandwidth extension off. The quantization noise is
shaped above the band of interest. The band of interest (bandwidth) is determined by the
Setting
slope low
slope normal; default setting
Setting
≤ 0.035 × full scale (−29 dBFS)
> 0.035 × full scale (−29 dBFS)
> 0.07 × full scale (−23 dBFS)
> 0.105 × full scale (−19.5 dBFS)
1 section
11. The DPSA signal is used as a reference signal for switching power stage
Slope rise and fall times
DPSA input levels
All information provided in this document is subject to legal disclaimers.
Rev. 2 — 1 April 2011
8 sections
Figure
10 ns with V
2
Rise and fall times of the PWM output edges
40 ns with V
Number of power stage sections active
1
4
8
7.
3.4 W PDM input class-D audio amplifier
DDP
DDP
4 sections
DPSA signal
= 3.6 V
= 3.6 V
2 sections
010aaa713
TFA9881
© NXP B.V. 2011. All rights reserved.
Figure 8
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