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Power Analog Microelectronics Inc

www.poweranalog.com

Shutdown Operation

Internal Bias Generator Capacitor Selection

Power Supply Decoupling, CS

Selection of ROSC

BST_A and BST_B Capacitors

VCLAMP Capacitors

Internal Regulated 5-V Supply (AVDD)

The PAM8615 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 pull 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.

For the best power-off pop performance, the

amplifier should be set in shutdown mode prior to

removing the power supply voltage.

The internal bias generator (VCM) provides the

internal bias for the preamplifier stage. The

e xt e r n a l in p u t ca p a cit o r s a n d t h is in t e r n a l

reference allow the inputs to be biased within the

o p t i m a l c o m m o n - m o d e r a n g e o f t h e i n p u t

preamplifiers.

The selection of the capacitor value on the VCM

terminal is critical for achieving the best device

performance. During startup or recovery from

shutdown state, the VCM capacitor determines

the rate at which the am plifier starts up. 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 VCM

capacitor.

Another function of the VCM capacitor is to

bypass high frequency noise on the internal bias

generator.

The PAM8615 is a high-performance CMOS audio

amplifier that requires adequate power supply

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

0.1µF, is recommended, placing as close as

possible to the device's PVCC lead. To filter

l o w e r - f r e q u e n c y n o i s e s , a l a r g e a l u m i n u m

electrolytic capacitor of 470µF 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 switching frequency is determined by the

values of components connected to ROSC (pin

19) and calculated with the following equation:

The recommended values is

323 kHz.

The half H-bridge output stages use NMOS

transistors only. They therefore require bootstrap

capacitors for the high side of each output to turn

on correctly. An at least 220nF ceramic capacitor,

rated for at least 25V, must be connected from

each output to its corresponding bootstrap input.

Sp ecif ica lly, on e 22 0 nF cap a cito r m us t b e

connected from OUT_A to BST_A, and another

220nF capacitor from OUT_B to BST_B. It is

recommended to

replace 220nF for lower than 100Hz applications.

To ensure that the maximum gate-to-source

voltage for the NMOS output transistors not

exceeded, two 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.

The AVDD terminal is the output of an internally-

generated 5V supply, used for the oscillator,

preamplifier, and volume 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.

ROSC=100k

Ω for a

switching frequency of

use 1

μF BST capacitor to

PAM8615

16W/32W Stereo Class-D Audio Power Amplifier

02/2012 Rev1.1

pF

R

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OSC

osc

21

68

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