Diodes PAM8008 - Manual (Page 9)

PAM8008
Document number: DSxxxxx Rev. 1 - 0
9 of 14
www.diodes.com
October 2012
© Diodes Incorporated
PAM8008
A Product Line of
Diodes Incorporated
Application Information
Power Limit Function
When connect Pin 4 to GND or floating, the PAM8008 power is limited at 2.5W. Different from other company’s power limit, the power limit circuit
of PAM8008 sets a limit on the output peak voltage, and the value is lower than the supply voltage (V
DD
), it means the THD+N always lower than
10% when power limit works. When the PAM8008 enters in power limit mode, the gain changes depending on the input audio signal amplitude
and the attack, release time. The gain changes constantly as the audio signal increase or decrease. Every gain step size is about 0.4dB. If the
audio signal has near-constant amplitude or the maximum attenuation is 20dB, the gain does not change.
Anti-Saturation Function
When connect Pin 4 to high, the PAM8008 enters power limit or anti-saturation mode. Which mode is selected depending on V
DD
and input
audio signal amplitude. If the V
DD
< = 5V, it enters anti-saturation mode. If the V
DD
> 5V, it enters power limit mode. In anti-saturation mode, the
power is 2.3W and the THD+N is lower than 1% when V
DD
= 5V. If connect Pin 4 to V
DD
/2, it can disable power limit and antisaturation function.
Table 2. PAM8008 Power Limit and Anti-Saturation Varible Description
Varible Description Value
Gain
The max gain when the PAM8008 is not in power limit
and anti-saturation mode. 20dB
(Maximum)
Attack Time The minimum time between two gain decrements. 128µs
Release Time The minimum time between two gain increments. 256mS
Table 3. PAM8008 Power Limit and Anti-Saturation Mode Setting
PL Mode
PL = Floating or
PL = 0V to 0.2V
Power Limit
PL = 0.8V to VDD/2
Power Limit and
Anti-Saturation Off
PL = 3.8V to VDD
V
DD
> 5V, Power Limit
V
DD
< = 5V, Anti-Saturation
Noise Reduction Function
The gain of PAM8008 will reduce 6dB when there is no audio at the input of the amplifier for 8s. The gain will recover until the input signal is
above the noise threshold.The noise threshold is set by internal voltage.
Mute Operation
The MUTE pin is an input for controlling the Class-D output state of the PAM8008. A logic low on this pin enables the outputs, and a logic high
on this pin disables the outputs. This pin may be used as a quick disable or enable of the outputs without a volume fade. Quiescent current is
listed in the electrical characteristic table. The MUTE pin can be left floating due to the internal pull-down.
Shutdown Operation
In order to reduce power consumption while not in use, the PAM8008 contains shutdown circuit to tur n off the amplifier's bias circuit. The
amplifier is turned off when logic low is placed on the SD pin. By connecting the SD pin to GND, the PAM8008 supply current will be minimized
in idle mode. The SD pin can be left floating due to the internal pull-up.
For the best power on/off pop performance, the amplifier should be placed in the Mute mode prior to turning on/off the
power supply.