PAM8320 Datasheet, PDF (8/11 Pages) Diodes Incorporated – 20W Mono Class D Audio Amplifier

Power Supply Decoupling, CS
A PRODUCT LINE OF
DIODES INCORPORATED
PAM8320
The PAM8320 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 the oscillations causing by long lead length between the amplifier and
the speaker.
Optimum decoupling is achieved by using two different types of capacitors that target different types of noise on the power supply leads. Higher
frequency transients, spikes or digital hash should be filtered with a good low equivalent-series-resistance (ESR) ceramic capacitor with a value of
typically 0.1μF. This capacitor should be placed as close as possible to the PVCC pin of the device. Lower frequency noise signals should be
filtered with a large ceramic capacitor of 470μF or greater. It's recommended to place this capacitor 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 half H-bridge output stages use NMOS transistors therefore requiring bootstrap capacitors for the high side of each output to turn on correctly.
A ceramic capacitor 220nF or more rated for over 25V must be connected from each output to its corresponding bootstrap input. Specifically, one
220nF capacitor must be connected from OUTN to BSN and another 220nF capacitor from OUTP to BSP. It is recommended to use 1μF BST
capacitor to replace 220nF for lower than 100Hz applications.
VCLAMP Capacitors
To ensure that the maximum gate-to-source voltage for the NMOS output transistors is not exceeded, an internal regulator is used to clamp the
gate voltage. A 1µF capacitor 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.
Using low-ESR Capacitors
Low-ESR capacitors are recommended throughout this application section. A real (with respect to ideal) capacitor can be modeled simply as a
resistor in series with an ideal capacitor. The voltage drop across this resistor minimizes the beneficial effects of the capacitor in the circuit. The
lower the equivalent value of this resistance the more the real capacitor behaves as an ideal capacitor.
Short-circuit Protection
The PAM8320 has short circuit protection circuitry on the outputs to prevent damage to the device when output-to-output shorts (BTL mode),
output-to-GND shorts, or output-to-VCC shorts occur. Once a short-circuit is detected on the outputs, the output drive is immediately disabled.
This is not a latched fault, if the short is removed the normal operation is restored.
Thermal Protection
Thermal protection prevents the device from damage. When the internal die temperature exceeds a typical of 160°C the device will enter a
shutdown state and the outputs are disabled. This is not a latched fault, once the thermal fault is cleared and the temperature of the die decreased
by 40°C the device will restart with no external system interaction.
Over Voltage Protection and Under Voltage Lock-out (OVP and UVLO)
An over voltage protection (OVP) circuit is integrated in PAM8320, when the supply voltage is over 18V the OVP is active and then the output
stage is disabled. The PAM8320 will auto recovery when the supply voltage is lower than the OVP threshold.
The PAM8320 incorporates circuitry designed to detect low supply voltage. When the supply voltage drops to 4.4V or below, the PAM8320 goes
into a state of shutdown. When the supply voltage is higher than 4.5V normal operation is resumed.
PAM8320
Document number: DS36610 Rev. 1 - 2
8 of 11
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October 2013
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