PAM8603A Datasheet, PDF (12/16 Pages) Diodes Incorporated – ANTI-SATURATION FILTERLESS 3W CLASS-D STEREO AMPLIFIER WITH DC VOLUME CONTROL AND HEADPHONE OUTPUT

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PAM8603A
Application Information
Power Supply Decoupling
The PAM8603A is a high performance CMOS audio amplifier that requires adequate power supply decoupling to ensure the output THD and
PSRR are as low as possible. Power supply decoupling affects low frequency on the power supply leads for higher frey response. Optimum
decoupling is achieved by using two capacitors of different types that target different types of noise frequency transients, spike, or digital hash
on the line, a good low equivalent-series-resisitance (ESR) ceramic capacitor, typically 1.0µF, placed as close as possible to the device V_DD
terminal works best. For filtering lower-frequency noise signals, a large capacitor of 10µF (ceramic) or greater placed near the audio power
amplifier is recommended.
Input Capacitor (C_I)
Large input capacitors are both expensive and space hungry for portable designs. Clearly, a certain sized capacitor is needed to capacitor is
needed to couple in low frequencies without severe attenuation. But in many cases the speakers used in portable systems, whether internal or
external, have little ability to reproduce signals below 100Hz to 150Hz. Thus, using a large input capacitor may not increase actual system
performance. In this case, input capacitor (C_I) and input resisitance (R_I) of the amplifier form a high-pass filter with the corner frequency
determined equation below,
fC
=
1
2ΠR_I
CI
In addition to system cost and size, click and pop perfomance is affected by the size of the input coupling capacitor, C_I. A larger input coupling
capacitor requires more charge to reach its quiescent DC voltage (nominally ½ V_DD). This charge comes from the internal circuit via the
feedback and is apt to create pops upon device enable. Thus, by minimizing the capacitor size based on necessary low frequency response,
turn-on pops can be minimized.
Analog Refernce Bypass Capacitor (C_BYP)
Analog Refernce Bypass Capacitor (C_BYP) is the most critical capacitor and serves several important functions. During start-up or recovery from
shutdown mode, C_BYP determines the rate at which the amplifier starts up. The second function is to reduce noise produced by the power
supply caused by coupling into the output drive signal. This noise is from the internal analog reference to the amplifier, which appears as
degraded PSRR and THD+N.
A ceramic bypass capacitior (C_BYP) of 0.47µF to 1.0µF is recommended for the best THD and noise performance. Increasing the bypass
capacitor reduces clicking and popping noise from power on/off and entering and leaving shutdown.
Under Voltage Lock-Out (UVLO)
The PAM8603A incorporates circuitry designed to detect when the supply voltage is low. When the supply voltage drops to 1.8V or below, the
PAM8603A outputs are disable, are the device comes out of this state and states to normal functional once V_DD ≥ 2.0V.
Short Circuit Protection (SCP)
The PAM8603A has short circuit protection circuitry on the outputs that prevents the device from damage when output-to-output and output-to-
GND short. When a short circuit is detected on the outputs, the outputs are disabled immediately. If the short was removed, the device activates
again.
Over Temperature Protection
Thermal protection on the PAM8603A prevents the device from damage when the internal die temperature exceeds +135°C. There is a
15 degree tolerance on this point from device to device. Once the die temperature exceeds the thermal set point, the device outputs are
disabled. This is not a latched fault. The thermal fault is cleared once the temperature of the die is reduced by 30°C. This large hysteresis will
prevent motor boating sound well. The device begins normal operation at this point without external system interaction.
PAM8603A
Document number: DSxxxxx Rev. 1 - 2
12 of 16
www.diodes.com
November 2012
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