tfa9879hn NXP Semiconductors, tfa9879hn Datasheet - Page 21

• Manufacturer Part Number: tfa9879hn
• Description: Mono Btl Class-d Audio Amplifier For Portable Applications With Digital Input
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TFA9879_1
Preliminary data sheet
9.2.11 Power limiter
Table 12.
[1]
[2]
[3]
The power limiter controls the maximum output voltage in Amplifier mode. This feature
makes it possible to limit the output voltage across a peripheral (speaker) when
necessary.
The TFA9879 output voltage is dependent on:
The bass/treble output signal is connected to the power limiter input and is relative to the
Fraction of Full Scale (FFS), from 1 to +1.
Equation 10
between pins OUTA and OUTB in the audio bandwidth:
Equation 10
control and the R
The power limiter gain can be reduced in 249 steps of 0.5 dB in the range 0 dB to
124 dB.
V
Control value:
attack rate
0000
0001
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
0010
•
•
•
o
=
The control value is selected via bits AT_RATE in the DRC control register (see
The control value is selected via bits RL_RATE in the DRC control register (see
Default value.
The analog supply voltage on pin V
The gain of the power limiter (G)
The power limiter input signal (X
[3]



X
V
i
DDP

[1]
DRC attack and release rates
G
shows the relationship between these settings and the output voltage
only applies with no load and with clip control off (see

5.91
All information provided in this document is subject to legal disclaimers.
DSon
Attack rate (dB/ms)
3
2.7
2.25
1.8
1.35
0.9
0.45
0.225
0.15
0.11
0.09
0.075
0.065
0.06
0.055
0.05
of the power switches reduce the maximum clipped output signal.
Rev. 01 — 8 April 2010
X
X
i
I


G
G


5.91
5.91
Mono BTL class-D audio amplifier with digital input
i
)


DDP
V
V
DDP
DDP
Control value:
release rate
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
(V)
[3]
[2]
Release rate (dB/ms)
0.5
0.137
0.075
0.05
0.036
0.03
0.026
0.021
0.020
0.017
0.015
0.014
0.013
0.012
0.011
0.01
Section
Table
Table
TFA9879
© NXP B.V. 2010. All rights reserved.
28).
28).
9.3). Clip
21 of 60
(10)