PAM8620
15W Stereo Class-D Audio Power Amplifier with Power Limit
Application Information
MUTE Operation
decoupling to ensure the output total harmonic
distortion (THD) as low as possible. Power supply
decoupling also prevents oscillations caused by
long lead between the amplifier and the speaker.
The optimum decoupling is achieved by using two
capacitors of different types that target different
types of noise on the power supply leads. For
higher frequency transients, spikes, or digital
hash on the line, a good low equivalent-series-
resistance (ESR) ceramic capacitor, typically
1µF, is recommended, placing as close as
possible to the device’s VCC lead. To filter lower-
frequency noises, a large aluminum electrolytic
capacitor of 10µF or greater is recommended,
placing near the audio power amplifier. The 10µF
capacitor also serves as a local storage capacitor
for supplying current during large signal
transients on the amplifier outputs.
The MUTE pin is an input for controlling the output
state of the PAM8620. A logic high on this pin
disables the outputs and low enables the outputs.
This pin may be used as a quick disable or enable
of the outputs without a volume fade.
Shutdown Operation
The PAM8620 employs a shutdown operation
mode to reduce supply current to the absolute
minimum level during periods of non-use to save
power. The SD input terminal should be held high
during normal operation when the amplifier is in
use. Pulling SD low causes the outputs to mute
and the amplifier to enter a low-current state. SD
should never be left unconnected to prevent the
amplifier from unpredictable operation.
BSN and BSP Capacitors
For the best power-off pop performance, the
amplifier should be set in shutdown mode prior to
removing the power supply voltage.
The full H-bridge output stages use NMOS
transistors only. They therefore require bootstrap
capacitors for the high side of each output to turn
on correctly. A at least 220nF ceramic capacitor,
rated for at least 25V, must be connected from
each output to its corresponding bootstrap input.
Specifically, one 220nF capacitor must be
connected from xOUTP to xBSP, and another
220nF capacitor from xOUTN to xBSN. It is
recommended to use 1μF BST capacitor to
replace 220nF or lower than 100Hz applications.
Internal 2.5V Bias Generator Capacitor
Selection
The internal 2.5V bias generator (V2P5) provides
the internal bias for the preamplifier stage. The
external input capacitors and this internal
reference allow the inputs to be biased within the
optimal common-mode range of the input
preamplifiers.
VCLAMP Capacitors
The selection of the capacitor value on the V2P5
terminal is critical for achieving the best device
performance. During startup or recovery from
shutdown state, the V2P5 capacitor determines
the rate at which the amplifier starts up. When the
voltage on the V2P5 capacitor equals 0.75 x
V2P5, or 75% of its final value, the device turns on
and the class-D outputs start switching. The
startup time is not critical for the best de-pop
performance since any heard pop sound is the
result of the class-D output switching-on other
than that of the startup time. However, at least a
0.47µF capacitor is recommended for the V2P5
capacitor.
To ensure that the maximum gate-to-source
voltage for the NMOS output transistors not
exceeded, a internal regulators are used to clamp
the gate voltage. A 1µF capacitors must be
connected from VCLAMP to ground and must be
rated for at least 25V. The voltages at the
VCLAMP terminals vary with VCC and may not be
used to power any other circuitry.
Internal Regulated 5-V Supply (AVDD)
The AVDD terminal is the output of an internally-
generated 5V supply, used for the oscillator,
amplifier,power limit circuitry and logic control
circuitry. It requires a 0.1µF to 1µF capacitor,
placed very close to the pin to Ground to keep the
regulator stable. The regulator may not be used to
power any external circuitry.
Another function of the V2P5 capacitor is to filter
high frequency noise on the internal 2.5V bias
generator.
Power Supply Decoupling, CS
The PAM8620 is a high-performance CMOS audio
amplifier that requires adequate power supply
Power Analog Microelectronics,Inc
10/2012 Rev1.0
www.poweranalog.com
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