PAM8620

Document number: DSxxxxx Rev. 1 - 0

8 of 13

www.diodes.com

June 2013

© Diodes Incorporated

PAM8620

A Product Line of

Diodes Incorporated

Application Information

Test Setup for Performance Testing

Notes:

1. The AP AUX-0025 low pass filter is necessary for class-D amplifier measurement with AP analyzer.

2. Two 22µH inductors are used in series with load resistor to emulate the small speaker for efficiency measurement.

MUTE Operation

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.

For the best power-off pop performance, the amplifier should be set in shutdown mode prior to removing the power supply voltage.

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.

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.

Another function of the V2P5 capacitor is to filter high frequency noise on the internal 2.5V bias generator.

The PAM8620 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 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.

BSN and BSP Capacitors

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.