PAM8302L datasheet(9/13 Pages) PAM

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Power Analog Microelectronics, Inc

Application Information

www.poweranalog.com

PAM8302L

2.5W Filterless Class-D Mono Audio Amplifier

Maximum Gain

As shown in block diagram (page 2), the

PAM8302L has two internal amplifier stages. The

first stage's gain is externally con figurable, while

the second stage's is internally fixed. The closed-

loop gain of the first stage is set by selecting the

ratio of R to R while the second stage's gain is

fixed at 2x.The output of amplifier 1 serves as the

input to amplifier 2, thus the two amplifiers

produce signals identical in magnitude, but

different in phase by 180°. Consequently, the

differential gain for the IC is

A =20*log [2*(R /R )]

The PAM8302L sets maximum R =80kΩ, minimum

R =10kΩ, so the maximum closed-gain is 24dB.

capacitor is the best choice. When a polarized

capacitor is used, the positive side of the

capacitor should face the amplifier input in most

applications as the DC level is held at VDD/2,

which is likely higher than the source DC level.

Please note that it is important to confirm the

capacitor polarity in the application.

Power Supply Decoupling (Cs)

The PAM8302L is a high-performance CMOS

audio amplifier that requires adequate power

supply decoupling to ensure the output THD and

P S R R a s l o w a s p o s s i b l e . P o w e r s u p p l y

decoupling affects low frequency response.

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-

Input Capacitors (Ci)

resistance (ESR) ceramic capacitor, typically

1.0µF is good, placing it as close as possible to

In typical application, an input capacitor, Ci, is

the device VDD terminal. For filtering lower-

required to allow the amplifier to bias input

frequency noise signals, a capacitor of 10µF or

signals to a proper DC level for optimum

operation. In this case, Ci and the minimum input

larger, closely located to near the audio power

impedance Ri (10k internal) form a high pass filter

amplifier is recommended.

with a corner frequency determined by the

following equation:

Shutdown Operation

In order to reduce shutdown power consumption,

the PAM8302L contains shutdown circuitry for

turn off the amplifier. This shutdown feature turns

It is important to choose the value of Ci as it

the amplifier off when a logic low is applied on the

directly affects low frequency performance of the

SD pin. By switching the shutdown pin over to

circuit, for example, when an application requires

GND, the PAM8302L supply current draw will be

a flat bass response as low as 100Hz. Equation is

minimized in idle mode.

reconfigured as follows:

For the best power on/off pop performance,

the amplifier should be set in the shutdown

mode prior to power on/off operation.

As the input resistance is variable, for the Ci

value of 0.16μF, one should actually choose the

Ci within the range of 0.1μF to 0.22μF. A further

consideration for this capacitor is the leakage

path from the input source through the input

network (Ri, RF,Ci) to the load. This leakage

current creates a DC offset voltage at the input to

the amplifier that reduces useful headroom,

especially in high gain application. For this

reason, a low leakage tantalum or ceramic

11/2010 Rev 1.0

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