TFA9879 NXP Semiconductors, TFA9879 Datasheet - Page 45

• Manufacturer Part Number: TFA9879
• Description: The TFA9879 contains a processor that supports a range of sound processing featuresincluding a 5-band parametric equalizer, separate bass and treble control, a dynamicrange compressor, soft clip control and volume control
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TFA9879
Product data sheet
Fig 17. Optional low-pass LC filter
15.1.2 Output current limiting
15.2 PWM output filtering
15.3 Supply decoupling and filtering
The peak output current I
level is 1.3 A. During normal operation, the output current should not exceed this
threshold level, otherwise the audio signal will be distorted. The peak output current in
BTL configuration can be calculated using
where:
Example:
A 4
The TFA9879 PWM power stage is optimized to meet the legal limits (FCC) for radiated
emissions without requiring an external filter (speaker cable < 5 cm). But a low-pass LC
filter is recommended if a long speaker cable can’t be avoided or other components in the
application are sensitive to frequencies in the 10 MHz to 150 MHz range (e.g. an FM
tuner). The suggested differential low-pass filter consists of a ferrite bead inductor (Z >
80 Ω at 100 MHz) and a small ceramic capacitor of about 1 nF (see
A ceramic decoupling capacitor of between 1 μF and 10 μF should be placed close to the
TFA9879 to minimize the size of the high-frequency current loop, thereby optimizing EMC
performance. Optionally, a small 1 nF ceramic capacitor can be connected in parallel to
further reduce the impedance.
I
O max
V
R
R
(
DDP
L
DSon
Ω
= load resistance (Ω)
)
speaker can be used with a 5 V supply without triggering OCP.
≤
= power supply voltage (V)
= drain-source on-state resistance (Ω)
I
O OCP
CLASS-D AMPLIFIER
(
TFA9879
All information provided in this document is subject to legal disclaimers.
)
≤
------------------------------------ -
2
OUTA
OUTB
×
Rev. 02 — 15 October 2010
R
V
DSon
DDP
O(max)
+
R
is limited internally by OCP. The minimum OCP trigger
ferrite bead
L
≤
speaker cables > 5 cm
Mono BTL class-D audio amplifier with digital input
1.3A
1 nF
Equation
1 nF
010aaa626
14:
Figure
TFA9879
© NXP B.V. 2010. All rights reserved.
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