Pam8320 new product – Diodes PAM8320 User Manual
Page 7
PAM8320
Document number: DS36610 Rev. 1 - 2
7 of 11
October 2013
© Diodes Incorporated
PAM8320
New Product
A PRODUCT LINE OF
DIODES INCORPORATED
Dual-Side PCB
To achieve good heat dissipation the PCB's copper plate should be thicker than 35um and the copper plate on both sides of the PCB should be
utilized for heat sink.
The thermal pad on the bottom of the device should be soldered to the plate of the PCB and via holes (usually 9 to 16) should be drilled in the
PCB area under the device. Deposited copper on the vias should be thick enough so that the heat can be dissipated to the other side of the plate.
There should be no insulation mask on the other side of the copper plate. More vias can and should be added to the PCB around the device for
further thermal optimization.
How to Reduce EMI
Most applications require a ferrite bead filter for EMI elimination shown at Figure 1. The ferrite filter reduces EMI around 1MHz and higher. When
selecting a ferrite bead it should be chosen with high impedance at high frequencies but low impedance at low frequencies.
200pF
200pF
OUT+
OUT-
Ferrite Bead
Ferrite Bead
Figure 1: Ferrite Bead Filter to Reduce EMI
Shutdown Operation
The PAM8320 employs a shutdown operation mode to reduce supply current to the absolute minimum level during periods of non-use to save
power. The SDN input terminal should be pull high during normal operation. Pulling SDN low causes the outputs to be muted and the amplifier
enters a low-current state. SDN should never be left unconnected.
Anti-POP and Anti-Click Circuitry
The PAM8320 contains circuitry to minimize turn-on and turn-off transients or “click and pops”, where turn-on refers to either power supply turn-on
or device recover from shutdown mode. When the device is turned on, the amplifiers are internally muted. An internal current source ramps up the
internal reference voltage. The device will remain in mute mode until the reference voltage reach half supply voltage. As soon as the reference
voltage is stable, the device will begin full operation. For the best power-off pop performance, the amplifier should be set in shutdown mode prior
to removing the power supply voltage.
Internal Bias Generator Capacitor Selection
The internal bias generator (VCM) 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 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 amplifier 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.